Figure

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Sizes of cell structures, plotted on a logarithmic scale. Typical sizes are indicated. %

Granular endoplasmic. reticulum

Agranular endoplasmic reticulum

Electron Micrograph Golgi Apparatus

NucIgus

Mitochondria

Lysosomes

Golgi apparatus

FIGURE 3-3

Electron micrograph of a thin section through a portion of a rat liver cell.

From K. R. Porter in T. W. Goodwin and O. Lindberg (eds.), "Biological Structure and Function," vol. I, Academic Press, Inc., New York, 1961.

Granular endoplasmic. reticulum

Agranular endoplasmic reticulum

NucIgus

Mitochondria

Lysosomes

Golgi apparatus

FIGURE 3-3

Electron micrograph of a thin section through a portion of a rat liver cell.

From K. R. Porter in T. W. Goodwin and O. Lindberg (eds.), "Biological Structure and Function," vol. I, Academic Press, Inc., New York, 1961.

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

PART ONE Basic Cell Functions

Nucleus

Nucleolus Mitochondrion

Lysosome

Granular endoplasmic reticulum

Bound ribosomes

Free ribosomes

Agranular-

endoplasmic reticulum

Nucleus

Nucleolus Mitochondrion

Lysosome

Bound ribosomes

Free ribosomes

Agranular-

endoplasmic reticulum

Pictures Ribosomes

Plasma membrane Secretory vesicle

Centrioles Endosome

Microtubule

Peroxisome

Nuclear envelope Microfilaments

FIGURE 3-4

Structures found in most human cells. ^

Nuclear pore Golgi apparatus

Nuclear envelope Microfilaments

FIGURE 3-4

Structures found in most human cells. ^

Nuclear pore Golgi apparatus

Plasma membrane Secretory vesicle

Centrioles Endosome

Microtubule

Peroxisome most of the electrons must pass through the specimen, just as light passes through a specimen in a light microscope. However, electrons can penetrate only a short distance through matter; therefore, the observed specimen must be very thin. Cells to be observed with an electron microscope must be cut into sections on the order of 0.1 ^m thick, which is about one-hundredth of the thickness of a typical cell.

Because electron micrographs (such as Figure 3-3) are images of very thin sections of a cell, they can often be misleading. Structures that appear as separate objects in the electron micrograph may actually be continuous structures that are connected through a region lying outside the plane of the section. As an analogy, a thin section through a ball of string would appear as a collection of separate lines and disconnected dots even though the piece of string was originally continuous.

Two classes of cells, eukaryotic cells and prokary-otic cells, can be distinguished by their structure. The cells of the human body, as well as those of other mul-ticellular animals and plants, are eukaryotic (true-nucleus) cells. These cells contain a nuclear membrane surrounding the cell nucleus and numerous other membrane-bound structures. Prokaryotic cells, for example, bacteria, lack these membranous structures. This chapter describes the structure of eukaryotic cells only.

Compare an electron micrograph of a section through a cell (Figure 3-3) with a diagrammatic illustration of a typical human cell (Figure 3-4). What is immediately obvious from both figures is the extensive structure inside the cell. Cells are surrounded by a limiting barrier, the plasma membrane, which covers the cell surface. The cell interior is divided into a number of compartments surrounded by membranes. These membrane-bound compartments, along with some particles and filaments, are known as cell organelles (little organs). Each cell organelle performs specific functions that contribute to the cell's survival.

The interior of a cell is divided into two regions: (1) the nucleus, a spherical or oval structure usually near the center of the cell, and (2) the cytoplasm, the region outside the nucleus (Figure 3-5). The cytoplasm contains two components: (1) cell organelles and (2) the fluid surrounding the organelles known as the cy-tosol (cytoplasmic solution). The term intracellular fluid refers to all the fluid inside a cell—in other words, cytosol plus the fluid inside all the organelles, including the nucleus. The chemical compositions of the fluids in these cell organelles differ from that of the cytosol. The cytosol is by far the largest intracellular fluid compartment.

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

Cell Structure CHAPTER THREE

Cell Structure CHAPTER THREE

Plasma membrane

TABLE 3-1 Functions of Cell Membranes

(a) Cytoplasm

Organelles

(b) Cytosol

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  • regina
    What is the function of granular and agranular?
    7 years ago

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