Classes of Organic Molecules

I. Carbohydrates are composed of carbon, hydrogen, and oxygen in the proportions Cm(H2O)m.

a. The presence of the polar hydroxyl groups makes carbohydrates soluble in water.

b. The most abundant monosaccharide in the body is glucose (C6H12O6), which is stored in cells in the form of the polysaccharide glycogen.

II. Most lipids lack polar and ionized groups, a characteristic that makes them insoluble in water. a. Triacylglycerols (fats) are formed when fatty acids are linked to each of the three hydroxyl groups in glycerol.

b. Phospholipids contain two fatty acids linked to two of the hydroxyl groups in glycerol, with the third hydroxyl linked to phosphate, which in turn is linked to a small charged or polar compound. The polar and ionized groups at one end of phospholipids make these molecules amphipathic.

c. Steroids are composed of four interconnected rings, often containing a few hydroxyl and other groups.

III. Proteins, macromolecules composed primarily of carbon, hydrogen, oxygen, and nitrogen, are polymers of 20 different amino acids.

a. Amino acids have an amino (—NH2) and a carboxyl (—COOH) group linked to their terminal carbon atom.

b. Amino acids are linked together by peptide bonds between the carboxyl group of one amino acid and the amino group of the next.

c. The primary structure of a polypeptide chain is determined by (1) the number of amino acids in sequence, and (2) the type of amino acid at each position.

d. The factors that determine the conformation of a polypeptide chain are summarized in Figure 2-17.

e. Hydrogen bonds between peptide bonds along a polypeptide force much of the chain into an alpha helix.

f. Covalent disulfide bonds can form between the sulfhydryl groups of cysteine side chains to hold regions of a polypeptide chain close to each other.

g. Multimeric proteins have multiple polypeptide chains.

IV. Nucleic acids are responsible for the storage, expression, and transmission of genetic information.

a. Deoxyribonucleic acid (DNA) stores genetic information.

b. Ribonucleic acid (RNA) is involved in decoding the information in DNA into instructions for linking amino acids together to form proteins.

c. Both types of nucleic acids are polymers of nucleotides, each containing a phosphate group, a sugar, and a base of carbon, hydrogen, oxygen, and nitrogen atoms.

d. DNA contains the sugar deoxyribose and consists of two chains of nucleotides coiled around each other in a double helix. The chains are held together by hydrogen bonds between purine and pyrimidine bases in the two chains.

e. Base pairings in DNA always occur between guanine and cytosine and between adenine and thymine.

f. RNA consists of a single chain of nucleotides, containing the sugar ribose and three of the four bases found in DNA. The fourth base in RNA is the pyrimidine uracil rather than thymine. Uracil base-pairs with adenine.

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

Chemical Composition of the Body CHAPTER TWO

Chemical Composition of the Body CHAPTER TWO

KEY TERMS

REVIEW QUESTIONS

KEY TERMS

REVIEW QUESTIONS

atom

carbohydrate

1.

Describe the electric charge, mass, and location of

chemical element

monosaccharide

the three major subatomic particles in an atom.

proton

glucose

2.

Which four kinds of atoms are most abundant in the

neutron

pentose

body?

electron

hexose

3.

Describe the distinguishing characteristics of the

atomic nucleus

disaccharide

three classes of essential chemical elements found in

atomic number

sucrose

the body.

atomic weight

polysaccharide

4.

How many covalent bonds can be formed by atoms

isotope

glycogen

of carbon, nitrogen, oxygen, and hydrogen?

gram atomic mass

lipid

5.

What property of molecules allows them to change

trace element

fatty acid

their three-dimensional shape?

molecule

saturated fatty acid

6.

Describe how an ion is formed.

covalent bond

unsaturated fatty acid

7.

Draw the structures of an ionized carboxyl group

ion

monounsaturated fatty acid

and an ionized amino group.

cation

polyunsaturated fatty acid

8.

Define a free radical.

anion

eicosanoid

9.

Describe the polar characteristics of a water

electrolyte

arachidonic acid

molecule.

carboxyl group

triacylglycerol

10.

What determines a molecule's solubility or lack of

amino group

glycerol

solubility in water?

free radical

phospholipid

11.

Describe the organization of amphipathic molecules

polar covalent bond

steroid

in water.

hydroxyl group

protein

12.

What is the molar concentration of 80 g of glucose

polar molecule

amino acid

dissolved in sufficient water to make 2 L of solution?

nonpolar molecule

amino acid side chain

13.

What distinguishes a weak acid from a strong acid?

hydrogen bond

peptide bond

14.

What effect does increasing the pH of a solution

hydrolysis

polypeptide

have upon the ionization of a carboxyl group? An

solute

peptide

amino group?

solvent

glycoprotein

15.

Name the four classes of organic molecules in the

solution

conformation

body.

ionic bond

van der Waals forces

16.

Describe the three subclasses of carbohydrate

hydrophilic

alpha helix

molecules.

hydrophobic

beta sheet

17.

To which subclass of carbohydrates do each of the

amphipathic

disulfide bond

following molecules belong: glucose, sucrose, and

concentration

multimeric protein

glycogen?

molecular weight

nucleic acid

18.

What properties are characteristic of lipids?

mole

deoxyribonucleic acid (DNA)

19.

Describe the subclasses of lipids.

acid

ribonucleic acid (RNA)

20.

Describe the linkage between amino acids to form a

base

nucleotide

polypeptide chain.

strong acid

deoxyribose

21.

What is the difference between a peptide and a

weak acid

purine

protein?

acidity

adenine

22.

What two factors determine the primary structure of

pH

guanine

a polypeptide chain?

neutral solution

pyrimidine

23.

Describe the types of interactions that determine the

alkaline solution

cytosine

conformation of a polypeptide chain.

acidic solution

thymine

24.

Describe the structure of DNA and RNA.

biochemistry

ribose

25.

Describe the characteristics of base pairings between

macromolecule

uracil

nucleotide bases.

polymer

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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  • ralph
    What are the subclasses of organic molecules?
    2 years ago

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