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Low Carb Weekly Meal Plans Summary


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Carbohydrates and Lipids

Carbohydrates are a class of organic molecules that includes monosaccharides, disaccharides, and polysaccharides. All of these molecules are based on a characteristic ratio of carbon, hydrogen, and oxygen atoms. Lipids constitute a category of diverse organic molecules that share the physical property of being nonpolar, and thus insoluble in water Carbohydrates and lipids are similar in many ways. Both groups of molecules consist primarily of the atoms carbon, hydrogen, and oxygen, and both serve as major sources of energy in the body (accounting for most of the calories consumed in food). Carbohydrates and lipids differ, however, in some important aspects of their chemical structures and physical properties. Such differences significantly affect the functions of these molecules in the body.

Carbohydrates and Lipids 31

Carbohydrates contain carbon, hydrogen, and oxygen, usually in a ratio of 1 2 1. A. Carbohydrates consist of simple sugars (monosaccharides), disaccharides, and polysaccharides (such as glycogen). D. Proteins may be combined with carbohydrates, lipids, or other molecules.

Anaerobic Fermentation Of Carbohydrates

In human colonic microflora, the majority of bacteria use nondigestible carbohydrates as the main if not exclusive feeding substrates. The metabolism of these compounds is quantitatively more important than amino acid fermentation, especially in the cecum and ascending segment where substrate availability is greatest. Carbohydrate fermentation is thus an important force driving the micro ecology and the physiology of the large intestine.8 Even though a wide variety of anaerobic bacteria are capable of fermenting many different types of carbohydrate, they use a small number of metabolic pathways to produce a limited range of end products. The most important and most frequent nondigestible carbohydrates in human diet that serve as substrates for colonic fermentation are (Table 5.4)

Carbohydrates Sugars and Sugar Polymers

Cage Protein

The second class of biological molecules, the carbohydrates, is a diverse group of compounds. Carbohydrates contain primarily carbon atoms flanked by hydrogen atoms and hy-droxyl groups (H C OH). They have two major biochemical roles Some carbohydrates are relatively small, with molecular weights of less than 100. Others are true macromolecules, with molecular weights in the hundreds of thousands. There are four categories of biologically important carbohydrates, which we will discuss in turn Monosaccharides (mono-, one saccharide, sugar ), such as glucose, ribose, and fructose, are simple sugars. They are the monomers out of which the larger carbohydrates are constructed. The general formula for carbohydrates, CH2O, gives the relative proportions of carbon, hydrogen, and oxygen in a monosaccharide (i.e., the proportions of these atoms are 1 2 1). In disaccharides, oligosaccharides, and polysaccha-rides, these proportions differ slightly from the general formula because two hydrogens...

Ketogenic Diet Therapy

Although several factors are considered necessary for its efficacy, the diet's exact mechanism of action has not yet been determined. It is known that a high level of ketosis must be reached. Traditionally, ketosis has been monitored by measuring urinary acetoaeetate. Measurement of blood ketones (eg, p-hydroxybutyrate) may give a more accurate picture of ketosis level although this is not feasible for routine outpatient care. Strict adherence to the diet is essential since only a small variation in dietary intake can affect the maintenance of ketosis and thus seizure control. Food is usually divided into three meals per day. Intake between meals is restricted to those foods that provide little or no carbohydrates. These include sugar-free fruit-llavored drinks made w ith saccharin, sugar-free soda, water, or measured amounts of nuts or olives. The diet must be supplemented with a multivitamin and multimineral supplement as well as additional calcium. The carbohydrate content of all...

Digestion And Absorption Of Carbohydrates

Structure Glycogen

The digestion and absorption of dietary carbohydrates takes place in the small intestine. These are extremely efficient processes, in that essentially all of the carbohydrates consumed are absorbed. Carbohydrates are an extremely important component of food intake, since they constitute about 45 to 50 of the typical Western diet and provide the greatest and least expensive source of energy. Carbohydrates must be digested to monosaccha-rides before absorption. The Diet Contains Both Digestible and Nondigestible Carbohydrates Humans can digest most carbohydrates those we cannot digest constitute the dietary fiber that forms roughage. Carbohydrate is present in food as monosaccharides, disaccha-rides, oligosaccharides, and polysaccharides. The monosaccharides are mainly hexoses (six-carbon sugars), and glucose is by far the most abundant of these. Glucose is obtained directly from the diet or from the digestion of dis-accharides, oligosaccharides, or polysaccharides. The next most common...

Digestion and Absorption of Carbohydrates Lipids and Proteins

The caloric (energy) value of food is derived mainly from its content of carbohydrates, lipids, and proteins. In the average American diet, carbohydrates account for approximately 50 of the total calories, protein accounts for 11 to 14 , and lipids make up the balance. These food molecules consist primarily of long combinations of subunits (monomers) that must be digested by hydrolysis reactions into free monomers before absorption can occur. The characteristics of the major digestive enzymes are summarized in table 18.7.

Major Products of Anaerobic Fermentation of Carbohydrates and Proteins in the Human Large Bowel

Carbohydrates The recent development and validation of molecular methodologies (especially the fluorescent in situ hybridization technique using specific ribosomal RNA rRNA sequences known as the FISH method in Chapter 9, Section 9.3) has initiated very active research on the composition of human fecal flora. The experiments so far reported have already revealed the existence of yet unknown noncultivable genera and species. The number of bacteria expressed as colony-forming units (cfu) of the different species range from 102 up to 1010 per gram of fresh feces. Each species has its own nutrition requirements and produces a specific pattern of metabolic end products. The colonic microflora is acquired at birth and during the early days, weeks, and months after birth. It is recognized today that the composition of the first colonic microflora is a key element in the development of the immune system early in life. Furthermore, the maintenance of a well-balanced composition throughout life...

Digestion Of Carbohydrates In The Gastrointestinal Tract

Digestion Carbohydrates

In the human diet, the most common carbohydrates are starch, sucrose, lactose, fructose, glucose, and dietary fibers. Most ( 50-60 of daily intake) carbohydrates are starch, which is a mixture of linear (amylose) and branched (amylopectin) polymers of glucose with D-1, 4 and D-1, 4 + D-1, 6 linkages, respectively. Starch, as well as the disaccharides lactose and sucrose, is hydrolyzed in the upper part of the gastrointestinal system (Figure 4.1), essentially the oral cavity and the small intestine, whereas the dietary fibers are not. The monosaccharides that preexist in the diet (fructose and glucose) and that are produced by the hydrolysis of starch and disaccharides (lactose and sucrose) are absorbed and reach the systemic circulation via the portal vein. But the oligo- and monosaccharides that reach or are produced in the large bowel, essentially by bacterial hydrolysis of dietary fibers and, in some populations, lactose, are not absorbed but fermented. Strictly speaking, the...

In Vitro Models to Study the Fermentation of Carbohydrates by the Colonic Microflora

The most commonly used in vitro models to study anaerobic fermentation of carbohydrates by mixed bacteria population, particularly fecal bacteria, are 47 Batch culture fermenters (50-350 ml working volume) that are inoculated either with pure culture of selected genera or species of bacteria or with fecal slurry (5-10 w v fresh feces homogenized in anaerobic buffer pH 7.0 and subsequently sieved) and the carbohydrate ( 1 w v) to be studied. Feces are collected anaerobically from volunteers with no preceding history of gastrointestinal disorder and who have not been prescribed antibiotics for at least 3 months. Before incubation, the slurry is gazed out with argon leaving a slight positive pressure of gas. The fermenters are then incubated for up to 48 h and samples of gas and liquid are taken for analyses at regular time intervals. The gas samples are analyzed for H2, CH4, and CO2 concentrations by gas liquid chromatog-raphy. In the liquid samples, the concentration of SCFAs is...

In Vivo Models to Study the Fermentation of Carbohydrates by the Colonic Microflora

In vivo fermentation of nondigestible carbohydrates can be studied both in experimental and domestic animals as well as in pets or in human volunteers. To study fermentation of dietary carbohydrates in humans, two major approaches are used The other approach to study fermentation of dietary carbohydrates in humans is rather straightforward. It consists in collecting feces after oral feeding and quantitatively measuring the concentration of the residual carbohydrate. If all fecal samples are collected over, e.g., 24 or 48 h, the test allows the determination of the proportion of the carbohydrate that has been digested and or fermented. But if adequate tests have demonstrated that the product is nondigestible (see Chapter 4, Table 4.1), then it is a measure of fermentation and, if the feces contain no residual carbohydrate, then the carbohydrate tested is completely fermentable. In the in vivo tests just described, both in animals and in humans, change in pH and an increase in the fecal...


Although carbohydrates account for only about 1 percent of the body weight, they play a central role in the chemical reactions that provide cells with energy. Carbohydrates are composed of carbon, hydrogen, and oxygen atoms in the proportions represented by the general formula Cn(H2O)n, where n is any whole number. It is from this formula that the class of molecules gets its name, carbohydrate water-containing (hydrated) carbon atoms. Linked to most of the carbon atoms in a carbohydrate are a hydrogen atom and a hydroxyl group The presence of numerous hydroxyl groups makes carbohydrates readily soluble in water. Most carbohydrates taste sweet, and it is among the carbohydrates that we find the substances known as sugars. The simplest sugars are the monosaccha-rides (single-sweet), the most abundant of which is glucose, a six-carbon molecule (C6H12O6) often called blood sugar because it is the major monosaccharide found in the blood. Most monosaccharides in the body contain five or six...

Antigens And Their Receptors

Since antigens can be of almost any chemical composition, the proteins and carbohydrates present in the membranes of our cells may be antigenic if the cells are introduced into another person or an animal. It was just this principle that was exploited in the production of monoclonal antibodies. Injecting human cells into mice (where they are recognised as foreign) meant that mice produced antibodies to the different molecules on the surfaces of the cells. By fusing a single antibody producing B cell with a replicating, transformed, cell the product was an immortalised clone of cells constantly producing antibody of a single specificity. That allowed us to identify individual molecules (antigens) on the surface of cells and to use them to identify and classify different cell types. Thus, a molecule on the surface of a cell (i.e. inserted through the membrane of the cell) may also be referred to as a surface antigen.

Life and Chemistry Large Molecules

These meteorites suggest that life is not found only on Earth, but they do not answer the question of how or where life arose from nonliving matter. We begin this chapter by presenting two hypotheses for the origin of life on Earth. After discussing these hypotheses, we take a detailed look at the four kinds of large molecules that characterize living organisms proteins, carbohydrates, lipids (fats), and nucleic acids.

Structure And Catalysis

7 Carbohydrates and Glycobiology 238 was removed from the cells into the chemists' laboratories, to be studied there by the chemists' methods. It proved, too, that, apart from fermentation, combustion and respiration, the splitting up of protein substances, fats and carbohydrates, and many other similar reactions which characterise the living cell, could be imitated in the test tube without any cooperation at all from the cells, and that on the whole the same laws held for these reactions as for ordinary chemical processes.

Sources Of Antibodies

Antibodies are synthesized by lymphocytes. Lymphocytes may be T ( thymus)-processed or B ( bone marrow)-processed. Antibodies are made by B-lymphocytes and exist in two forms, either membrane bound or secreted. B-lymphocytes use membrane-bound antibody to interact with antigens. A B-cell makes antibodies all of the same specificity, i.e., able to react with the same antigenic determinants its progeny (as a consequence of mitotic division) are referred to as a clone. The clone will continue making antibody of the same specificity. Simultaneously, there will be many other clones of different specificity. This is known as a polyclonal response. Antigens have determinants called epitopes. Epitopes are molecular shapes recognized by antibodies, which recognize one epitope rather than whole antigen. Antigens may be proteins, lipids, or carbohydrates, and an antigen may consist of many different epitopes and or may have many repeated epitopes.

The Digestive Functions

It includes masticating, mixing, and triturating the food to disrupt the matrix followed by solubilization of the components and micelle formation with the nonsoluble products (especially fats), and, finally, partial or complete hydrolysis of the complex food molecules (peptides and proteins, lipids, some complex carbohydrates, and nucleic acids).

Types of Supporting Matrix

Electrophoresis is conducted in a sievelike supporting matrix, such as filter paper, cellulose acetate membrane, or, more commonly, a gel. Gels are made primarily of starch, agarose, or polyacrylamide. Starch and agarose are carbohydrates. Gel electrophoresis typically uses agarose, a purified form of agar-agar, extracted from seaweeds (marine red algae). Agarose gels have large pores, which allow large molecules to pass through.

Study in Ileal Pouch Anal Anastomosis IPAA

In a study of some years ago 96 , our aim was to determine whether a meal induces specific motor patterns in longstanding IPAA. Nine patients (6M, 3F) aged 35-58 (median 49) years were studied 1-10 (median 6.8) years after ileostomy closure. Two had a W-pouch and seven had a J-pouch. None of the patients showed endoscopic findings of pouchitis daily bowel movements were 2-6 (median 4.6). After at least 12 h of fasting, an 8-channel perfused catheter with an open central lumen was placed by means of a guide-wire inserted during a regular colonoscopy. Recording ports, 15 cm apart, were positioned such that four were in the proximal small bowel, three in the reservoir and one on the internal anal sphincter. After at least 1 h after colonoscopy, we recorded pressure signals for 120 min before the ingestion of a 1 000-Kcal meal with 40, 30 and 30 of lipids, proteins and carbohydrates respectively. Postprandial recording continued for a further 60 min. Small bowel and pouch...

Endomembrane System And Golgi Complex

Have direct, permanent connections with the endomembrane system (such as between the endoplasmic reticulum and the nuclear envelope), whereas other components share membrane and contents by trafficking vesicles (membrane-bound packages) from one component to another (for example, the ER sends numerous vesicles to the Golgi complex) across the cytosol. The endomembrane system is responsible for processing, sorting, and packaging membrane material, proteins embedded in membranes, and large water-soluble molecules (such as proteins or carbohydrates), either for export from the cell (called exocytosis) or for use within the cell. The endoplasmic reticulum is the ultimate source of all the membranes of the endo-membrane system.

Economic Growth and Modernization

Generally, as incomes rise and populations become more urban, diets high in complex carbohydrates and fibre give way to varied diets with a higher proportion of fats, saturated fats and sugars. Recent analyses of economic and food availability data, however, reveal a major shift in the structure of the global diet over the last 30 years. Innate preferences for palatable diets coupled with the greater availability of cheap vegetable oils in the global economic have resulted in greatly increased fat consumption and greater dietary diversity among low income nations. As a result, the classic relationship between incomes and fat intakes has been lost, with the so-called 'nutrition transition' now occurring in nations with much lower levels of gross national product than previously. The process is accelerated by rapid urbanization (21). The ramifications of programming are immense for countries such as India and China where a large proportion of infants are still born undernourished. If...

Smooth and Rough ER Functions

Facturing cell are transported into the rough ER for further processing. Once inside, they are shaped into the correct three-dimensional configuration that will be useful outside the cell. Necessary chemicals, such as carbohydrates or sugars, are then added to complete the proteins. The ER then transports these proteins to other areas of the ER, called transitional Er, where they are packed in vesicles to be sent to the Golgi complex for export, or secretion, to other parts of the plant. Occasionally, some of the completed proteins are transported to areas of the manufacturing cell where they are needed. Because the smooth ER does not have attached ribosomes, it appears relatively smooth when viewed through an electron microscope. It also appears to bud off from vesicles that contain material from the lumen of the ER. Using the many different enzymes that are anchored to its walls, the smooth ER is involved with the synthesis, secretion, and storage of lipids as well as the...

Characteristics A Organism

S. aureus is a spherical gram-positive bacterium (coccus) that on microscopic examination appears in pairs, short chains, or bunched, grape-like clusters. Some strains are capable of producing a highly heat-stable protein toxin, which is capable of causing illness in humans. Other salient characteristics are that they are nonmotile and asporogenous capsules may be present in young cultures but are generally absent in stationary phase cells (9). Staphylococcus species are aerobes or facultative anaerobes and have both respiratory and fermentative metabolism. They are catalase positive and utilize a wide variety of carbohydrates. Amino acids are required as nitrogen sources, and thiamine and nicotinic acid are also required. When grown anaerobically, they appear to require uracil (10).

Isotope labeling experiments revealed the steps of the Calvin Benson cycle

To identify the sequence of reactions by which CO2 ends up in carbohydrates, it was necessary to label CO2 so that it could be followed after being taken up by a photosynthetic cell. In the 1950s, Melvin Calvin, Andrew Benson, and their colleagues used radioactively labeled CO2 in which some of the carbon atoms were not the normal 12C, but its radioisotope 14C. Although 14C is distinguished by its emission of radiation, chemically it behaves virtually identically to nonra-dioactive 12C. In general, enzymes do not distinguish between isotopes of an element in their substrates, so 14CO2 is treated the same way by photosynthesizing cells as 12CO2. rapidly killed the cells, extracted their carbohydrates, and separated the different compounds from one another by paper chromatography. Many compounds, including monosaccharides and amino acids, contained 14C (Figure 8.12).

Resource Requirements

Insects feed on a wide variety of plant, animal, and dead organic matter. Dietary requirements for all insects include carbohydrates amino acids cholesterol B vitamins and inorganic nutrients, such as P, K, Ca, Na, etc. (R. Chapman 2003, Rodriguez 1972, Sterner and Elser 2002). Insects lack the ability to produce their own cellulases to digest cellulose. Nutritional value of plant material often is limited further by deficiency in certain requirements, such as low content of N (Mattson 1980), Na (Seastedt and Crossley 1981b, Smedley and Eisner 1995), or linoleic acid (Fraenkel and Blewett 1946). Resources differ in ratios among essential nutrients, resulting in relative limitation of some nutrients and potentially toxic levels of others (Sterner and Elser 2002). High lignin content toughens foliage and other tissues and limits feeding by herbivores without reinforced mandibles. Toxins or feeding deterrents in food resources increase the cost, in terms of search time, energy, and...

Variation in Food Quality

Food quality varies widely among resource types. Plant material has relatively low nutritional quality because N usually occurs at low concentrations and most plant material is composed of carbohydrates in the form of indigestible cellulose and lignin.Woody tissues are particularly low in labile resources readily available to insects or other animals. Plant detrital resources may be impoverished in important nutrients as a result of weathering, leaching, or plant resorption prior to shedding senescent tissues.

Regulators of complement activation RCA family

One member of the RCA family is the C4-binding protein (C4BP). As its name suggests, it binds C4b which may be cleaved (and therefore inactivated) by the protease Factor I. The latter, in the presence of another member of the RCA family, Factor H, may cleave the a chain of hydrolysed C3 or C3b to form a partially degraded molecule, iC3b. This molecule does not play a part in the complement cascade but is capable of promoting phagocytosis. In addition, under appropriate conditions, Factor I can degrade iC3b further to C3dg. Regulation by Factors I and H is dependent upon the surface to which C3b is bound. If the surface is that of a microorganism, the C3b is protected from Factors H and I, which are unable to bind, and the complement cascade proceeds to its termination with the formation of the MAC. By contrast, when C3b is bound to host cell membranes, Factors H and I are able to interact with it causing its degradation and preventing the continuation of the pathway. This difference...

The Immune Response To Bacteria

Recognition of microbial invaders is based on the fact that for virtually every category of microbe, there are certain structural features that the microbe cannot change without losing its ability to survive and function in its own hostile and life-threatening environment. Structural features of living organisms are based on standard biochemical molecules such as proteins, carbohydrates, fats, and even DNA or RNA. When a microbe has a chemically based structure it simply cannot alter, that structure becomes a prime target for a chemically based (innate) immune defense.

Neutropenia Associated with Metabolic Diseases

The presenting clinical features in neutropenia associated with metabolic diseases (Table 9-6) are lethargy, vomiting, ketosis, and dehydration during the neonatal period, failure to thrive, and growth retardation. The marrow is hypoplastic in these conditions, with decreased numbers of myeloid precursors. Idiopathic hyperglycin-emia and methylmalonic acidemia also have associated thrombocytopenia.

Monosaccharides and Disaccharides

The simplest of the carbohydrates, the monosaccharides, are either aldehydes or ketones with two or more hydroxyl groups the six-carbon monosaccharides glucose and fructose have five hydroxyl groups. Many of the carbon atoms to which hydroxyl groups are attached are chiral centers, which give rise to the many sugar stereoisomers found in nature. We begin by describing the families of monosaccharides with backbones of three to seven carbons their structure and stereoisomeric forms, and the means of representing their three-dimensional structures on paper. We then discuss several chemical reactions of the carbonyl groups of mono-saccharides. One such reaction, the addition of a hydroxyl group from within the same molecule, generates the cyclic forms of five- and six-carbon sugars (the forms that predominate in aqueous solution) and creates a new chiral center, adding further stereochemical complexity to this class of compounds. The nomenclature for unambiguously specifying the...

Specific saturated and trans fatty acids and CHD risk

Different specific saturated fatty acids may have different effects on CHD risk. In particular, there is a growing interest in stearic acid as a substitute for TFA to give texture and solidity to foods. Metabolic studies show that lauric acid most markedly increases total and LDL cholesterol, whereas stearic acid somewhat lowers total and LDL cholesterol when it replaces carbohydrates (Fig. 1.2) (Mensink et al., 2003). However, lauric acid also has the strongest HDL raising effect, whereas stearic acid raises HDL cholesterol less than other saturated or cis-unsaturated fatty acids. The net effect is that lauric and stearic acid have less unfavourable effects on the total to HDL cholesterol ratio than myristic and palmitic acids. However, consequences of these differences for CHD risk are unclear. Saturated fatty acids tend to occur together in diets due to shared food sources, there are therefore hardly any epidemiological data for specific saturated fatty acids. Only one published...

Health Related Effects Associated with Colonic Microflora

Hydrolysis and fermentation of nondigestible carbohydrates (dietary content (low pH). In the left distal (descending segment and sigmoid-rectum) colon, the availability of substrates (especially carbohydrates) is usually low, bacteria grow slowly, and pH is close to neutrality (7).1 Moreover, the breakdown and fermentation of organic materials reaching the large bowel is a complex process that involves different groups of bacteria with miscellaneous and complementary activities. Bacteria are generally not specific for particular metabolic activities they all metabolize

Protein and Amino Acid Metabolism

Unlike most carbohydrates and fats, amino acids contain nitrogen atoms (in their amino groups) in addition to carbon, hydrogen, and oxygen atoms. Once the nitrogen-containing amino group is removed, the remainder of most amino acids can be metabolized to intermediates capable of entering either the glycolytic pathway or the Krebs cycle.

Immune Response Viral Infections

In response to the constant threat of invasion by microorganisms and viruses, vertebrates have evolved an elaborate set of defensive measures, called, collectively, the immune system. During the initial encounter with a virus, the immune system of the host recognizes as foreign certain viral macromolecules (proteins, carbohydrates) called antigens, which elicit several kinds of responses to eliminate the virus and to prevent reinfection. Cells of the humoral immune system (B lymphocytes) respond to an antigenic stimulus by producing and secreting specific immunoglobulins called antibodies cells of the cell-mediated immune system (T lymphocytes) respond by secreting several cytokines which regulate the immune response by coordinating the activities of the various types of cells involved. These lymphocytes bear highly specific receptors that enable them to interface with discrete sites on the virion or on viral peptides, known as antigenic determinants or epitopes This specific...

Generalized Bone Marrow Disorders

Hyperglycinemia with ketosis and the closely related metabolic disorder of methyl-malonic acidemia may cause periodic thrombocytopenia, as well as neutropenia, during infancy. Infants with these metabolic disorders present with lethargy, vomiting, and ketosis during the neonatal period. A similar disorder, isovaleric acidemia, is associated with a generalized marrow hypoplasia causing thrombocytopenia and neu-tropenia. Neonatal thrombocytopenic purpura has been reported in infants born to hyperthyroid mothers. The mechanism has not been defined.

Healthy Eating for Children

Meals should provide adequate amounts of protein, carbohydrates. and fat (Tables 8-2 to 8-6).14 Fat in moderate amounts is an essential component of any diet. It is recommended that no less than M)c of the calories in a child's diet come from fat. unless the child is on a special high or low fat diet.1 If the child is eating a lot of fast and or junk food, it is likely that their dietary fat intake is too high.1 Carbohydrates prov ide a feeling of fullness and substance in a meal. Children generally enjoy starchy foods and thus do not have to be persuaded to eat them. The diet that is too high in carbohydrates may be too low in fat. however, and is likely to be unsatisfying.1

Play a key role in the digestion of food and in the uptake and release of fatty acids by tissues

Seeds that contain lipid may have as much as 80 of their dry weight represented by triacylglycerols. Plants such as soybean face two particular problems in using such energy reserves. First, these plants have to mobilize the lipid rapidly and break it down to useful products. This overall process involves the synthesis of degradative enzymes as well as the production of the necessary membranes and organelles that are the sites of such catabolism. Secondly, plants with lipid-rich seeds must be able to form water-soluble carbohydrates (mainly sucrose) from the lipid as a supply of carbon to the rapidly elongating stems and roots. Animals are unable to convert lipid into carbohydrate (Fig. 3.9) because of the decarboxylation reactions of the Krebs (tricarboxylic acid) cycle (isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase). Thus, for every two carbons entering the Krebs Fig. 3.9 Permitted and forbidden interconversions of fats, carbohydrates and proteins in animals. Fig. 3.9...

Metabolic Pathways in Plants

The Metabolic Pathways Photosynthesis

The light reactions of photosynthesis generate ATP and NADPH, which are used to synthesize carbohydrates. These compounds can then be used in cellular respiration to provide energy for processes such as active transport and an-abolism. Both cellular respiration and fermentation can occur in plants, although the former is far more common. Plant cellular respiration, unlike photosynthesis, takes place both in the light and in the dark. Because glycolysis occurs in the Some G3P from the Calvin-Benson cycle can be converted to pyruvate, the end product of glycolysis. This pyru-vate can be used in cellular respiration for energy, or its carbon skeletons can be used anabolically to make lipids, proteins, and other carbohydrates (see Figure 7.17).

Food Absorption Requires a High Blood Flow to Support the Metabolism of the Mucosal Epithelium

The active absorption of amino acids and carbohydrates and the metabolic processing of lipids into chylomicrons by mucosal epithelial cells place a major burden on the mi-crovasculature of the small intestine. There is an extensive network of capillaries just below the villus epithelial cells that contacts these cells. The villus capillaries are unusual in that portions of the cytoplasm are missing, so that the two opposing surfaces of the endothelial cell membranes appear to be fused. These areas of fusion, or closed fenestrae, are thought to facilitate the uptake of absorbed materials by capillaries. In addition, intestinal capillaries have a higher filtration coefficient than other major organ systems, which probably enhances the uptake of water absorbed by the villi (see Chapter 16). However, large molecules, such as plasma proteins, do not easily cross the fenestrated areas because the reflection coefficient for the intestinal vasculature is greater than 0.9, about the same as in...

Rubisco catalyzes RuBP reaction with O2 as well as CO2


As its full name indicates, rubisco is a carboxylase (adding CO2 to the acceptor molecule RuBP) as well as an oxygenase (adding O2 to RuBP). These two reactions compete with each other. So when RuBP reacts with O2, it cannot react with CO2. This reaction reduces the overall CO2 that is converted to carbohydrates, and therefore limits plant growth.

Exercise USome Metabolic Activities of Bacteria

Some bacteria ferment simple carbohydrates, producing acidic, alcoholic, or gaseous end products. Many different species are distinguished on the basis of the carbohydrates they do or do not attack, as well as by the nature of end products formed during fermentation. Still others break down more complex carbohydrates, such as starch. The nature of products formed in amino acid metabolism also provides information as to the identification of bacterial species. The production of visible pigments distinguishes certain types of bacteria.

Catabolism and anabolism involve interconversions using carbon skeletons

A hamburger or veggiburger contains three major sources of carbon skeletons for the person who eats it carbohydrates, mostly as starch (a polysaccharide) lipids, mostly as triglycerides (three fatty acids attached to glycerol) and proteins (polymers of amino acids). Looking at Figure 7.17, you can see how each of these three types of macromolecules can be used in catabolism or anabolism.

Macronutrient Effects On Intake

This confers a much greater sensitivity to changes in the pool size for carbohydrate, than for fat, and Flatt argues that this modulates later consumption in order to restore the equilibrium. Based on this hypothesis the status of the body's carbohydrate store is critical in determining intake and implies that individuals eat sufficient food to defend their carbohydrate stores. Thus on a diet with a low carbohydrate fat ratio the total amount of energy consumed in order to provide sufficient carbohydrate will be greater than when consuming a diet with a high carbohydrate fat ratio. This scenario must inevitably lead to fat deposition which will persist until such time as the substrate mixture being oxidized matches that of the habitual diet (i.e. RQ FQ). Fat accumulation is thus interpreted as a response to a high fat diet (25). Evidence for this theory comes from prolonged feeding trials in mice (7). Specifically there was a negative correlation between changes...

Isabel M Vazquez MS RD and Jan P Hangen MS RD

II is important for children to eat a variety of foods that can provide them with the proper intake of carbohydrates. protein, fat. minerals, and vitamins. Each child grows at a unique rate and therefore has unique nutritional needs. Children's behaviors and food preferences are also unique. The nutritional needs of children should be balanced with their food likes and dislikes. The following are general guidelines to follow when feeding infants, children, and adolescents they should not be viewed as precise. It is important to recogni e that children eat differently every day and that they should be allowed to follow their own internal hunger and satiety cues.

DNA in Aquatic Ecosystems

In aquatic ecosystems, the organic carbon inventory is largely dominated by non-living materials (i.e. detrital carbon) present in both the dissolved and particulate states, whose cycling is primarily mediated by heterotrophic prokaryotes. The labile fraction of the organic carbon pool in the oceans is mainly composed of simple (i.e. monomeric) and combined biochemical compounds. Among the biochemical classes of organic compounds, DNA ranks fourth after carbohydrates, proteins and lipids 1 . In aquatic environments, DNA is present in different forms (1) associated with living organisms (i.e. intracellular DNA) (2) encapsulated by proteins (i.e. viral DNA) (3) free (i.e. soluble DNA) and (4) adsorbed to detrital and or mineral particles 2 . Since viruses are a group of biological entities with a genome 3 , only the two latter forms can be considered genuine extracellular DNA. DNA associated with living biomass is the ultimate source of extracellular DNA because cell-free DNA synthesis...

Exercise Activities of Bacterial Enzymes

As catalysts, enzymes promote changes only in very specific substances or substrates, as they are often called. Thus, in the previous exercise, the changes produced in simple carbohydrates and in starch substrates were brought about by different, specific enzymes. We have seen the activity of an enzyme with a different kind of outcome, the breakdown of an antimicrobial agent (see Experiment 15.3), but the principle is exactly the same. In the latter instance, the beta-lactamase enzyme penicillinase brought about a change in the substrate penicillin.

Evidence Linking Fat To Obesity

Increased following ingestion of a high fat diet (20-22). In addition, a number of studies have suggested that appetite control is dissociated from fat since energy intake of a subsequent meal was not suppressed by adding up to 60 g fat (2.3 MJ) to the previous meal (for review see Astrup and Raben (19)). Likewise, one study demonstrated that 2-year maintenance of weight loss was more successful on an ad libitum low fat diet than on calorie counting (23). Finally, randomized dietary fat intervention studies consistently show that weight is lost on a calorically unrestricted low fat diet, although rates of weight loss per day are modest (ranges between 17 g and 37 g per day) (18). The specific mechanism for dietary fat in obesity development is generally believed to depend on passive over-consumption on the high fat diet, due mainly to its high energy density and also palatabil-ity related factors. However, the effect is likely to vary under different circumstances. For instance, fat...

Lectin Carbohydrate Interactions Are Very Strong and Highly Specific

Lymphocytes Sugar Code

In addition to these very specific interactions, there are more general interactions that contribute to the binding of many carbohydrates to their lectins. For example, many sugars have a more polar and a less polar side (Fig. 7-36) the more polar side hydrogen-bonds with the lectin, while the less polar undergoes hydro-phobic interactions with nonpolar amino acid residues. The sum of all these interactions produces high-affinity binding (Kd often 10 8 m or less) and high specificity of lectins for their carbohydrates. This represents a kind of information transfer that is clearly central in many processes within and between cells. Figure 7-37 summarizes some of the biological interactions mediated by the sugar code. SUMMARY 7.4 Carbohydrates as Informational Molecules The Sugar Code X-ray crystallography of lectin-sugar complexes shows the detailed complementarity between the two molecules, which accounts for the strength and specificity of their interactions with carbohydrates.

Evidence Unlinking Fat From Obesity

Genetic susceptibility for weight gain may be influenced by dietary factors, such as fat intake (46). Indeed, a few studies have indicated that development of obesity is, in part, due to differential effects of fat in the diet for those who are genetically predisposed, compared to those who are not (47-49). In this context, studies in both animals and humans have demonstrated that food intake seems to play a specific role for obesity development in association with a predisposition to obesity (37,50,51). For instance, Sclefani and Assimon (52) found that obesity prone mice ate more high fat, but less sugar-rich foods than leanness prone mice. In addition, obesity prone mice have been found to gain weight at a much faster rate than wild-type mice fed the same high fat diets (50), suggesting a gene-environment interaction between the high fat diet and the subsequent weight gain. Furthermore, compared to non-obese controls, impaired ability to increase the fat carbohydrate oxidation...

Ju h Macromolecules Giant Polymers

Extra Alveolar Vessels Septal

You eat an apple, the molecules you take in include carbohydrates, lipids, and proteins that can be refashioned into the special varieties of those molecules used by humans. Macromolecules are giant polymers (poly-, many -mer, unit ) constructed by the covalent linking of smaller molecules called monomers (Table 3.1). These monomers may or may not be identical, but they always have similar chemical structures. Molecules with molecular weights exceeding 1,000 are usually considered macromolecules, and the proteins, polysaccharides (large carbohydrates), and nucleic acids of living systems certainly fall into this category. Each type of macromolecule performs some combination of functions energy storage, structural support, protection, catalysis, transport, defense, regulation, movement, and information storage. These roles are not necessarily exclusive. For example, both carbohydrates and proteins can play structural roles, supporting and protecting tissues and organisms. However, only...

Multienzyme Metabolic Pathways

Combinations of possible control points, the overall result is staggering. The details of regulating the many metabolic pathways at the enzymatic level are beyond the scope of this book. In the remainder of this chapter, we consider only (1) the overall characteristics of the pathways by which cells obtain energy, and (2) the major pathways by which carbohydrates, fats, and proteins are broken down and synthesized. The functioning of a cell depends upon its ability to extract and use the chemical energy in organic molecules. For example, when, in the presence of oxygen, a cell breaks down 1 mol of glucose to carbon dioxide and water, 686 kcal of energy is released. Some of this energy appears as heat, but a cell cannot use heat energy to perform its functions. The remainder of the energy is transferred to another molecule that can in turn transfer it to yet another molecule or to energy-requiring processes. In all cells, from bacterial to human, the primary molecule to which energy...

Nutritional Counseling

Another aspect of nutritional counseling is to avoid the excess intake of carbohydrates and increase the reliance of the individual on fats and proteins to improve the respiratory quotient. Because the metabolism of fats and proteins yield a lower CO2 load per unit of energy, these forms of nutrition place a lower respiratory burden on the individual. Appropriate intake of trace minerals, potassium, magnesium, phosphate, and calcium needs to be assured in order to avoid any negative impact on respiratory muscle function.

Digestion As A Chemical Process

The digestive process begins in the oral cavity. The saliva contains enzymes which initiate the digestion of complex carbohydrates. c. In the small intestines, there are digestive enzymes for all three classes of foodstuffs--carbohydrates, lipids, and proteins. Enzymes for completing the digestion of these three classes are found in the fluids produced by the pancreas and glands in the mucosa of the small intestines. Moreover, there is a fluid called bile that is produced by the liver and stored in the gallbladder for release into the small intestines. Bile helps in the digestion of lipids.

Nutrition Strategies For Insulin Therapy

It is important for the patient to consistently follow the meal plan as the insulin program is initiated and insulin doses are adjusted. Consistent timing of meals and snacks as well as the quantity of foods consumed (especially carbohydrates) will help to optimize glycemic control. As the patient learns the onset, peak, and duration of his or her insulins, adjustments can be made in the meal plan, insulin program, or both to achieve target blood glucose levels (2).

Adhesionblockade effect

Adhesion-blockade of enteric pathogens. Several carbohydrates, such as 0.1 fucose or 0.5 glucose, as well as LPS (10 (ig ml) isolated from Shigella jlexneri strongly inhibit the adherence of shigellae to guinea pig colonic cells. Fucose-containing peptides from hLF also inhibit the adhesion of S. Jlexneri to colonic epithelial cells (Izhar et al., 1987)

Overcoming the Manifestations of Syndrome X

Dietary recommendations to reduce CHD have until quite recently been based upon the principle that hypercholesterolemia (more specifically, an elevated LDL cholesterol level) is the only CHD risk factor that needs to be addressed. The result has been almost total emphasis on the use of low-fat-high-carbohydrate (CHO) diets. More to the point, advice to replace saturated fat (SF) with CHO in order to lower LDL cholesterol concentrations continues to be given, regardless of how insulin resistant the individual. Unfortunately, this dietary approach will make all of the manifestations of syndrome X worse. The greater the CHO content in an isocaloric diet, the more insulin must be secreted in order to maintain glucose homeostasis. This poses no danger to insulin-sensitive individuals, but low-SF high-CHO diets will significantly increase the already high day-long plasma insulin concentrations in patients with syndrome X. As a consequence, fasting plasma TG concentrations will increase, as...

Ribosome units released

Carbohydrates, lipids, proteins, and nucleic acids, together with the characteristic synthetization processes and the genetic code, constitute the basic biochemical building elements of all life forms on Earth. As the type and frequency of the building blocks are controlled by the master plan on the DNA, one can call this entire building industry the DNA machinery. It will be mentioned below that in the early history of the Earth, when life started, there were other types of machinery.

Intestinal Absorption

7.4 INULIN AND OLIGOFRUCTOSE AS LOW-CALORIE CARBOHYDRATES CONCLUSION Using U-14C -labeled synthetic oligofructose and a radiochemical balance study in humans, Hosoya et al. have established a caloric value of 1.5 kcal g or 6.3 kJ g.39 In addition to the uncertainty factors discussed above and used in these energy calculations to account for the efficiency of the fermentation process and the metabolism of the fermentation end products by host cells, it must be kept in mind that inulin and oligofructose may have additional gastrointestinal as well as systemic effects that may influence the energy balance of the host. In the context of this discussion, it is worth mentioning that inulin-type fructans may inhibit hepatic lipogenesis (see Chapter 11) and, as shown in rats, may induce a reduction in body fat deposition.40 41 Like other dietary fibers that cross the small intestine without being digested, inulin-type fructans may affect the small intestinal transit time of other nutrients.42...

Hypoglycemia Associated With Insulin Therapy

Hypoglycemia should be treated immediately if the blood glucose level is less than 70 mg dl, even if the patient is not experiencing symptoms. The patient's first step in treating hypoglycemia is to check his or her blood glucose level if possible. Foods and beverages that contain quick-acting carbohydrates are recommended to treat hypoglycemic reactions because foods that are high in fat take longer to elevate blood glucose levels. Patients should always keep a source of quick-acting carbohydrate on hand to treat hypoglycemic reactions. If

Structural Organisation Of Human Collectins

The basic structure of collectins is organised into four regions (Kishore and Reid 2001, Lu et al. 2002, Holmskov et al. 2003) (i) a cysteine-containing N-terminus (required for disulfide-dependent oligomerisation) that is linked to (ii) a triple-helical collagen region composed of repeating Gly-X-Y triplets (associated with maintaining the molecular shape, stability and state of oligomerisation), followed by (iii) an a-helical, coiled-coil neck region (whose main function is protein trimeri-sation), and (iv) a globular structure at the C-terminus comprising a C-type lectin or CRD (that mediates calcium-dependent ligand-binding to entities such as pathogens via carbohydrates, or surfactant phospholipids, etc.) (Figure 1). The CRDs are arranged as trimers at the end of the triple-helical collagen region (Kishore and Reid, 2001). The CRDs can engage a range of pathogens and ligands, including fungi (Table 1) due to its carbohydrate or charge pattern recognition properties whereas the...

Antibodyindependent Cl Assical Pathwayactivation

Select proteins, carbohydrates, viruses, and bacteria can activate Clq in the fluid phase and without antibody. Polyanions such as polyinosine, polyguanilic acid, lecithin, and sphingomyelin are potent activators. C-reactive protein (CRP) can also activate Clq indirectly following interactions with polyanions.

Withindepot Sitespecific Properties And Obesity

Guinea-pigs are grazers, whose natural diet is very low in fat, and contains mostly unsaturated fatty acids, so this minor modification of the diet probably induced a major departure from the normal situation. These data suggest that circulating lipids affect local interactions between adipose tissue and lymphoid cells, though the mechanism remains unknown. A high fat diet or hyperlipidaemia may impair local immune responses, and reduce the sensitivity of adipocytes to cytokines. Such properties could be relevant to known associations between high fat diet, obesity and certain forms of cancer (42,50,51).

Solutions To Exercises Lesson

The three categories of foodstuffs are carbohydrates, lipids, and proteins. Other necessary items include water, minerals, and vitamins. (para 6-3b, c) 18. The saliva contains enzymes that initiate the digestion of complex carbohydrates. In the small intestines, there are digestive enzymes for carbohydrates, lipids, and proteins. These enzymes are found in the fluids produced by the pancreas and glands in the mucosa of the small intestines. Moreover, the liver produces a fluid called bile, which is stored in the gallbladder for release into the small intestines this fluid helps in the digestion of lipids. (para 6-17)

Relationship Between Obesity And Type 2 Diabetes Mellitus

Extensively on the societal factors which have accompanied or induced the changes leading to the New World syndrome, and which have led to identification of obesity as a global epidemic (25). The WHO Report cited such components of modernization as the development of market economies, reliance on imported non-traditional foods, increasing urbanization, changing occupational structures, increasing socioeconomic status, increases in animal fat and animal protein intake, decreases in vegetable fat and vegetable protein intake, reduction in total and specifically complex carbohydrates, and increases in sugar intake. The net effect of these factors might be viewed as providing an unrestrained environment in which genetic potential becomes fully expressed. Alternatively, the environment may be interacting in such a way as to be detrimental to 'normal' gene expression.

Gas Exchange In Plants

All living organisms continually produce gases via metabolic and cellular activities, and the vast majority of living things are in one way or another in intimate contact with a gaseous medium. In most instances, therefore, there is ample opportunity for all organisms to exchange gases with the environment. The gaseous balance in plants is quite complex because plant cells carry on both respiration and photosynthesis. Plants respire in much the same way as animals oxygen is used to oxidize carbohydrates, and carbon dioxide and water are produced as waste products. The photosynthetic process requires an input of carbon dioxide and water. These two reactants are used to produce carbohydrates, and oxygen is released as a waste product. Under normal conditions, photosynthetic rates are higher than respiration rates thus, there is a net increase in oxygen production, accompanied by a net increase in the usage of carbon dioxide. On balance, therefore, plants use carbon dioxide and produce...

Box 141 The World Of Biochemistry

Deep-sea explorations have revealed many species of marine life at great ocean depths, where the oxygen concentration is near zero. For example, the primitive coelacanth, a large fish recovered from depths of 4,000 m or more off the coast of South Africa, has an essentially anaerobic metabolism in virtually all its tissues. It converts carbohydrates to lac-tate and other products, most of which must be excreted. Some marine vertebrates ferment glucose to ethanol and CO2 in order to generate ATP.

Box 142 The World Of Biochemistry

Brewers prepare beer by ethanol fermentation of the carbohydrates in cereal grains (seeds) such as barley, carried out by yeast glycolytic enzymes. The carbohydrates, largely polysaccharides, must first be degraded to disaccharides and monosaccharides. In a process called malting, the barley seeds are allowed to germinate until they form the hydrolytic enzymes required to break down their polysaccharides, at which point germination is stopped by controlled heating. The product is malt, which contains enzymes that catalyze the hydrolysis of the 3 linkages of cellulose and other cell wall polysaccharides of the barley husks, and enzymes such as a-amylase and maltase.

Changes in Acid Production May Help Protect Blood pH

This scenario is especially important when the endogenous production of these acids is high, as occurs during strenuous exercise or other conditions of circulatory inadequacy (lactic acidosis) or during ketosis as a result of uncontrolled diabetes, starvation, or alcoholism. These effects of pH on endogenous acid production result from changes in enzyme

Other Risks Of Intensified Insulin Therapy Diabetic Ketoacidosis and Hyperinsulinaemia

Although severe hypoglycaemia was indisputably the major metabolic side-effect of intensive insulin therapy in the DCCT, concerns have been expressed that some intensive treatment regimens may also increase the risk of developing ketosis. This was primarily related to the use of CSII (with insulin pump therapy) and was thought to relate to the absence of any intermediate-acting or background insulin in the event of pump failure. In insulin pump therapy, soluble or fast-acting analogue insulin is delivered steadily by a slow infusion of very low doses throughout the day. The insulin delivery is accelerated before meals to deliver boluses, akin to giving intermittent subcutaneous injections of short-acting insulin. Because the basal insulin is delivered in a very low volume and there is no depot of intermediate-acting insulin in the subcutaneous tissues to act as a reservoir, an interruption in the delivery of insulin can rapidly lead to hyperglycaemia and even ketosis, especially if...

Glycolysis And Fermentation

The simple sugar glucose is generally considered the starting point for looking at glycolysis and fermentation. Glucose is a simple carbohydrate, consisting of carbon, hydrogen, and oxygen. Most glucose is produced by plants organisms that cannot photosynthesize must obtain glucose (or more complex carbohydrates) from their surroundings. Animals obtain food molecules by eating. Simpler forms of life, such as bacteria and yeast, simply absorb their food from their environment.

ApoB and lipoprotein metabolism

Several common mutations have been found in the human apoB gene. Owing to the protein's dual role as a transport protein and a peripheral recognition signal for LDL clearance, these mutations have been shown to result either in reduced VLDL secretion or in hypercholesterolaemia (LDL accumulation). Several studies have investigated the influence of some of the apoB polymorphisms on responses to change from high-fat to low-fat diets (or the opposite). Three polymorphisms have been mostly associated with diet-induced LDL cholesterol changes a XbaI restriction site located in exon 26, an EcoRI site in exon 29 and a MspI site. Lopez-Miranda et al. (1997) reported that subjects with the homozygous absence of the XbaI site have a greater postprandial response (retinyl palmitate and apoB48 levels) to a fat-rich meal than the subjects with the presence of the XbaI site. More recently, it has been shown that a high-fat diet also induced a larger increase in plasma LDL cholesterol in subjects...

Translocation of Substances in the Phloem

Photosynthesis takes place in the mesophyll cells and, in C4 plants, in the bundle sheath cells of the leaf (see Figure 8.16). The products of photosynthesis (primarily carbohydrates) diffuse to the nearest small vein, where they are actively transported into sieve tube elements.

Genetic influences on the metabolic syndrome

Numerous epidemiological studies have pointed out the role played by both environmental factors (e.g. lack of physical exercise, smoking) and nutritional factors (calorically dense, low-fibre and high-fat diets) (Zhu et al., 2004). On the other hand, some recent clues that heredity plays an important role came from the discovery of certain rare but major mutations associated with severe forms of glucose impairment (Yki-Jarvinen, 1997). The role played by genetic factors has also been highlighted by several epidemiological studies. It has been shown, for example, that impairment of insulin action could be inherited in the offspring of diabetic probands (Vauhkonen et al., 1998). Similarly, when the various determinants of glucose homeostasis are analysed in different populations, only the resistance of glucose intake, which is directly linked to impaired function of insulin, correlates with genetic background (Ferrannini et al., 2003).

Some plants produce chemical defenses

Although a plant cannot flee its herbivorous enemies, it may be able to defend itself chemically. Many plants attract, resist, and inhibit other organisms by producing special chemicals known as secondary metabolites. Primary metabolites are substances, such as proteins, nucleic acids, carbohydrates, and lipids, that are produced and used by all living things. Secondary metabolites are substances that are not used for basic cellular metabolism. Although all organisms use the same kinds of primary metabolites, plants can differ as radically in their secondary metabolites as they do in their external appearance.

Mechanisms Of Postcessation Weight Gain

In addition to short-term increases in total energy intake, smoking cessation has been associated with changes in specific components of dietary intake. Selective increases in dietary fat (56), carbohydrates (57), sucrose (56,58), and alcohol (41) have been observed following smoking cessation. Overall, increases in dietary intake after smoking cessation appear to be due to between-meal snacking, rather than from a general increase in food consumption during meals. Gilbert and Pope (59) found that energy intake from meals was similar during 24-hour periods of ad libitum smoking and abstinence, but that intake from between-meal snacks increased 50 in men and 94 in women during abstinence.

Studying Vertebrate Muscle

Once the various subcellular components are isolated, they can be subjected to a wide variety of biochemical tests to determine what type of molecules they contain (such as proteins, lipids, or carbohydrates), how much of each type they contain, and the exact chemical composition of these molecules (such as the amino acid sequence of a protein). In the case of muscle cells, much of the interest has centered on the large quantities of the proteins actin and myosin which they have been found to contain. Using isolated actin and myosin, scientists have learned much about their functions in muscle cells. In particular, it is now known that these two proteins are the molecules which generate the contractile forces which muscle cells are capable of producing. The precise molecular mechanisms are still unknown, but great progress has been made in discovering how actin and myosin accomplish the generation of contractile forces.

Suggested Reading

Digestion and absorption of carbohydrates and proteins. In Johnson LR, ed. Physiology of the Gastroin testinal Tract. 3rd Ed. New York Raven, 1994,-1723-1749. Boyer JL, Graf J, Meier PJ. Hepatic transport systems regulating pH, cell volume and bile secretion. Annu Rev Physiol 1992,54 415-438. Choudari CP, Lehman GA, Sherman S. Pancreatitis and cystic fibrosis gene mutations. Gastroenterol Clin North Am 1999,28 543-549.

Biosynthetic Controls on Lipid S13C Values

Ences in 513C values among compound classes (e.g. lipids vs. carbohydrates as described above) and also between 513C values of individual lipids within a structural class. The traditional paradigm regarding biosynthetic isotope effects is that fractionation occurs during formation of acetyl-CoA with the strongest depletion occurring at the carboxyl carbon 155 presumably this fractionation is associated with either the oxidation of pyruvate to acetyl-CoA by pyruvate dehydrogenase 156 or conversion of acetyl phosphate to acetyl-CoA by phosphotransacetylase 157 . Monson and Hayes 155 determined that the kinetic isotope effect associated with pyruvate dehydrogenase in E. coli was 23 (spdh), but this full effect is rarely expressed because of Rayleigh distillations (such that the residual pyruvate carbon pool becomes progressively enriched in 13C as the reaction progresses). Instead, the fractionation expressed during decarboxylation is (1 - f )spdh 155 , where f is the fraction of...

Ecosystem Structure

Autotrophs are those organisms capable of fixing (acquiring and storing) inorganic resources in organic molecules. Photosynthetic plants, responsible for fixation of abiotic carbon into carbohydrates, are the sources of organic molecules. This chemical synthesis is powered by solar energy. Free-living and symbiotic N-fixing bacteria and cyanobacteria are an important means of converting inorganic N2 into ammonia, the source of most nitrogen available to plants. Other chemoau-totrophic bacteria oxidize ammonia into nitrite or nitrate (the form of nitrogen available to most green plants) or oxidize inorganic sulfur into organic compounds. Production of autotrophic tissues must be sufficient to compensate for amounts consumed by heterotrophs.

Lipoprotein metabolism

In the mid-1980s, investigators began to debate the question of the ideal substitute for SFA calories carbohydrate or unsaturated fatty acids, specifically MUFAs under stable weight conditions. The results of two similar studies conducted by Grundy (1986) and Mensink and Katan (1987) reported a similar total cholesterol-lowering effect of both a high-fat diet (40 of energy) rich in MUFA and low in SFAs and a low-fat carbohydrate-rich diet. Although both diets lowered total and LDL cholesterol, the high-MUFA diet did not lower high-density lipoprotein (HDL) cholesterol or increase triglycerides, as did the carbohydrate-rich diet. The carbohydrate-rich diet lowered HDL cholesterol by 14-22 and markedly elevated triglycerides (22-39 ). Table 4.1 Expected healthy effects with the replacement of dietary monounsaturated fat for saturated fat. CHO carbohydrates

Marilyn Bernard MS RD

The ketogenic diet is an eating plan that allows the body to stay in a constant state of ketosis. It is used therapeutically to manage refractory seizures or to help reduce the side effects of antiepileptic medications. The diet consists of individually calculated amounts of foods to achieve a high-fat, low-carbohydrate, and lowered-protein diet. Nearly a century ago, several investigators noticed that epileptic patients had fewer seizures while fasting or while on a water diet. ' The original ketogenic diet was developed in the 1920s to mimic the biochemical changes associated with starvation. The diet was an effective and widely used therapy for seizures until the 1950s, when antiepileptic medications became increasingly available. Recently, the diet has regained popularity as an effective alternative or adjunct to these medications. A variety of studies have shown significant reductions in seizure frequency with the ketogenic diet.2-' A recent study reported the efficacy rate of...

Abiotic and Biotic Pools

Resources from abiotic pools are not available to all organisms but must be transformed (fixed) into biologically useful compounds by autotrophic organisms. Photosynthetic plants acquire water and atmospheric or dissolved carbon dioxide to synthesize carbohydrates, which then are stored in biomass. Nitrogen-fixing bacteria and cyanobacteria acquire atmospheric or dissolved N2 and convert it into ammonia, which they and some plants can incorporate directly into amino acids and nucleic acids. Nitrifying bacteria oxidize ammonia into nitrite and nitrate, the form of nitrogen available to most plants. These autotrophs also acquire other essential nutrients in dissolved form. The living and dead biomass of these organisms represents the pool of energy and nutrients available to heterotrophs.

Polysaccharide Capsule

Capsules are produced by organisms in a variety of habitats, many of which are found in the marine environment (245). Expression is considered a basic cellular function, as judged by its early evolution and development (245). Pathogenic bacteria are often classified on the basis of the complex polysaccharides found on the surface, usually capsular polysaccharides or lipopolysaccharides. It is common in the clinical microbiology laboratory to use reactivity with antisera that specifically recognize these various cell surface carbohydrates for identification purposes.

Tissue Specific Metabolism The Division of Labor

Each tissue of the human body has a specialized function, reflected in its anatomy and metabolic activity (Fig. 23-12). Skeletal muscle allows directed motion adipose tissue stores and releases energy in the form of fats, which serve as fuel throughout the body the brain pumps ions across plasma membranes to produce electrical signals. The liver plays a central processing and distributing role in metabolism and furnishes all other organs and tissues with an appropriate mix of nutrients via the bloodstream. The functional centrality of the liver is indicated by the common reference to all other tissues and organs as extrahepatic or peripheral. We therefore begin our discussion of the division of metabolic labor by considering the transformations of carbohydrates, amino acids, and fats in the mammalian liver. This is followed by brief descriptions of the primary metabolic functions of adipose tissue, muscle, brain, and the medium that interconnects all others the blood.

Satiating Properties Of Macronutrients

In contrast to popular belief an overall nutritional goal in dietary treatment of obesity is to increase the proportion ofcarbohydrates in the diet since carbohydrate rich foods have high satiating properties, especially when compared to fat. Numerous studies have demonstrated that fat not only is the most energy dense macronutrient but also has weak satiating properties (5). Table 30.1 summarizes the characteristics of macronutrients in their ability to regulate daily dietary food intake. A key issue in dietary treatment strategies for obesity has thus been not only to reduce the daily energy intake but also in particular to cut fat to 30 or less of total energy intake. Carbohydrates generally appear in starchy and fibre-rich natural products, which means that a diet rich in natural carbohydrates will have a low energy density and thus enhance satiety. If fat intake is reduced, the protein proportion of the daily food intake will increase. The role of the protein in a diet for weight...

Will you die of cardiovascular disease

Healthy arteries have a smooth internal lining of en-dothelial cells (Figure 49.14a). This lining can be damaged by chronic high blood pressure, smoking, a high-fat diet, or microorganisms. Deposits called plaque begin to form at sites of endothelial damage. First, the damaged endothelial cells attract certain white blood cells to the site. These cells are then joined by smooth muscle cells migrating from the deeper layers of the arterial wall. Lipids, especially cholesterol, are deposited in these cells, so that the developing plaque becomes fatty. Fibrous connective tissue made by the invading smooth muscle cells in the plaque, along with deposits of calcium, makes the artery wall less elastic hence, hardening of the arteries. The growing plaque deposit narrows the artery and causes turbulence in the blood flowing

Preparation and Precursors

Activity (enzymatic breakdown of proteins). Protein synthesis diminishes, and there is an increase in the enzymatic degradation of ribonucleic acid (RNA). There is also an increase in the hydrolytic breakdown of carbohydrates. Finally, destruction of the green pigment, chlorophyll, is accompanied by increased visibility of the yellow or orange pigments called carotenoids, which were previously masked by chlorophyll. Most of the protein, carbohydrates, RNA, and chlorophyll degradation products are rapidly transported out of the senescing leaf. The final result is the production of yellowish, dead leaves.

Carbohydrate metabolism

Experience with healthy Mediterranean populations, having a low rate of ischaemic coronary heart disease, explains the great interest placed on the study of the effects of MUFA on CHO metabolism. One of the first studies, carried out by Garg et al. (1988), showed that feeding type 2 diabetic patients with a high-fat diet enriched in MUFA (50 fat and 33 of calories as MUFA) resulted in a lower insulin requirement, lower plasma glucose concentration and lower triglyceride plasma concentration versus a low-fat, high-CHO diet (60 CHO, 25 fat and 9 as MUFA). Using a similar design, Bonanome et al. (1991) failed to demonstrate this improvement. However, different studies since 1995 have confirmed the initial data, showing that MUFA-enriched diets reduce the requirement for insulin and decrease plasma concentration of glucose and insulin. By replacing complex CHO with MUFA in the diet, Parillo et al. (1992) found a decrease in plasma triglyceride, postprandial plasma glucose and insulin

Food provides carbon skeletons for biosynthesis

Every animal requires certain basic organic molecules that it cannot synthesize for itself, but needs as building blocks for its own complex organic molecules (see Chapter 7). An example of such a required carbon skeleton is the acetyl group (Figure 50.4). Animals cannot make acetyl groups from carbon, oxygen, and hydrogen molecules they must obtain acetyl groups by metabolizing carbohydrates, fats, or proteins obtained by eating other organisms.

Function of Abscission

Will still occur when flowers are removed from the plant soon after being formed. Although competition for nutrients may not be the sole cause of the phenomenon, the mobilization of substances such as amino acids and carbohydrates from the leaves to other metabolic sinks, such as the fruit, is definitely linked to the initiation of senescence. Several of the plant hormones or other factors that stimulate mobilization also hasten senescence. Hence, it is possible that the competition for nutrients triggers the production of some unknown senescence hormone by the fruit or some other competing plant part. This theoretical substance would be transported to the leaves, where it would initiate mobilization of leaf contents. This mobilization might enhance senescence, which, in turn, might trigger the metabolic reactions that lead to abscission of the leaves.

Biomarkers discovery and complexity of biological systems

The second issue the investigator will face is the immense number and diversity of biomolecules present in a biological system. These molecules can range from simple organic or inorganic compounds such as glucose and Na+ to large complex biopolymers such as lipids, proteins, and carbohydrates. To further complicate the picture, biopolymers can be mixed with each other to form lipopolysaccharides, glycoproteins, lipoproteins, etc. From this complicated picture the investigator

Nutrients are absorbed in the small intestine

The final digestion of proteins and carbohydrates that produces absorbable products takes place among the microvilli. The mucosal cells with microvilli produce peptidases, which cleave polypeptides into tripeptides, dipeptides, and individual amino acids that the cells can absorb. These cells also produce the enzymes maltase, lactase, and sucrase, which cleave the common disaccharides into their constituent, ab-sorbable monosaccharides glucose, galactose, and fructose.

So What Can And Should Women Do To Reduce Their Chances Of Getting A Heart Problem

If it is high, indicating diabetes, lose weight, avoid sugars and carbohydrates (pasta, rice, bread, chocolate and sweets, chips, and most high-calorie snacks), do daily exercise, and have the blood sugar rechecked. If it remains high, diabetes is possible, and this may need further tests.

UpDownregulation of Components of TAG Storage and Mobilization 11481 HSL

Paired glucose and severely blunted glucose-stimulated insulin secretion upon challenge with a high-fat diet. Their islets displayed both elevated HSL activity and forskolin-induced lipolysis compared with wild-type islets, which resulted in significantly reduced TAG levels in transgenic compared with wild-type islets provided the mice have been fed a high-fat diet. Thus, the rate of influx of NEFA into TAG of the islet LD and the capacity to mobilize this TAG pool seem to determine the emergence of islet lipotoxicity. This is in accord with the recently reported inverse correlation between apoptosis and TAG accumulation in cultured -cells, suggesting a cytoprotective function of TAG in cytoplasmic LD formed by normal -cells against NEFA-induced islet dysfunction 517 . Moreover, prolonged high-fat feeding of mice is accompanied by down-regulation of the expression of islet HSL 518 . Consequently, physiological down-regulation of HSL or pharmacological inhibition of HSL and possibly of...

Nutritional physiology and ecology

Insect Physiology

A major theme of this chapter is compensatory feeding. In spite of the enormous variation in the quality of plant food, insects obtain their requirements by means of flexible feeding behaviour and nutrient utilization (Slansky 1993). There are three basic categories of compensatory responses shown by phytophagous insects (Simpson and Simpson 1990) increased consumption in order to obtain more of a limiting nutrient such as nitrogen, dietary selection of a different food to complement a limiting nutrient, or increased digestive efficiency to make the best use of a nutrient. The mechanisms of compensatory feeding have been studied in some detail for the major nutrients, proteins and carbohydrates. To avoid difficulties in interpreting experiments, the use of artificial diets is essential, in spite of their ecological limitations (Simpson and Simpson 1990). Another pervasive theme is nitrogen limitation. Insect herbivores tend to be limited by nitrogen because their C N ratio is so much...

Glycogenesis and Glycogenolysis

Cells cannot accumulate very many separate glucose molecules, because an abundance of these would exert an osmotic pressure (see chapter 6) that would draw a dangerous amount of water into the cells. Instead, many organs, particularly the liver, skeletal muscles, and heart, store carbohydrates in the form of glycogen. Figure 5.4 Glycogenesis and glycogenolysis. Blood glucose entering tissue cells is phosphorylated to glucose 6-phosphate. This intermediate can be metabolized for energy in glycolysis, or it can be converted to glycogen ( 1 ) in a process called glycogenesis. Glycogen represents a storage form of carbohydrates that can be used as a source for new glucose 6-phosphate (2) in a process called glycogenolysis. The liver contains an enzyme that can remove the phosphate from glucose 6-phosphate liver glycogen thus serves as a source for new blood glucose.

Laboratory Manual andMicrobiology in Action Intestinal Tract Companies 2003 Workbook in Microbiology 7e

One type of kit, the Enterotube II (BD Diagnostic Systems), is a tube of 12 compartmentalized, conventional agar media that can be inoculated rapidly from a single isolated colony on an agar plate (see colorplate 36). The media provided indicate whether the organism ferments the carbohydrates glucose, lactose, adonitol, arabinose, sorbitol, and dulcitol produces H2S and or indole produces acetylmethylcarbinol deaminates phenylalanine splits urea decarboxylates lysine and or ornithine and can use citrate when it is the sole source of carbon in the medium. The mechanism of the other tests provided by the Enterotube II has been described in previous exercises or experiments (17, 18, 24.1). A third type of kit, MicroScan (Dade Behring), consists of a multiwell panel containing dried antimicrobial agents for susceptibility testing and biochemical reagents for identification of enteric and glucose nonfermenting gram-negative bacilli. The wells of the panel are inoculated with a standardized...

Exercise 8Culture Media

Aseptic Technique Pouring

First, a suitable culture medium must be provided, and it must contain the nutrients essential for the growth of the microorganism to be studied (see Exercise 2). Most media designed for the initial growth and isolation of microorganisms are rich in protein components derived from animal meats. Many bacteria are unable to break down proteins to usable forms and must be provided with extracted or partially degraded protein materials (peptides, proteoses, peptones, amino acids). Meat extracts, or partially cooked meats, are the basic nutrients of many culture media. Some carbohydrate and mineral salts are usually added as well. Such basal media may then be supplemented, or enriched, with blood, serum, vitamins, other carbohydrates and mineral salts, or particular amino acids as needed or indicated.

Characteristics Of Mannosebinding Receptors

Mammalian receptors recognising carbohydrate structures are called lectins. The lectins binding to mannose residues belong to the family of C-type lectin receptors (CLRs), the C indicating Calcium-dependency of sugar binding (Cambi and Figdor, 2003). This chapter will focus on transmembrane CLRs. Based on the orientation of their amino (N)-terminus, they can be grouped in type I (intracellular N-terminus) and type II receptors (extracellular N-terminus). CLRs are pattern recognition receptors whose primary function is to mediate antigen uptake (Figdor et al. 2002). This is in contrast to the other important family of PRRs, the Toll-like receptors (TLRs), that mainly induce cytokine signalling and immune activation after binding to PAMPs (Takeda et al. 2003). The key functional domain of CLRs mediating carbohydrate binding is the carbohydrate recognition domain (CRD). CLRs either contain one or many CRDs. The capacity of C-type lectins to sense microorganisms is highly dependent on the...

Inulin Type Fructans and Feed for Domestic Animals and pets

Another but still poorly understood application of inulin and oligofructose is in the reduction of fecal odor. The fermentation of carbohydrates, including oligosac-charides, reduces fecal ammonia, amine, and phenol concentrations,40 all of which have been implicated as the major sources of odorous feces.47-49 Because of increased human contact with animals and heightened awareness of environmental considerations, fecal odor is of concern to companion animal owners and livestock producers alike. In conclusion, some research exists concerning supplementation of inulin and oligofructose in the diets of companion animals and livestock. Studies to date indicate a positive effect of fructans on colonic microbial ecology, and host health and performance. However, much more research remains to be done to determine the appropriate role of these oligosaccharides in animal nutrition.

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