LECTURE 4
: CELL STRUCTURE AND FUNCTIONI. Types of cells.
A. Cells are the basic biological unit.
B. Two major types of cells: Prokaryotic cells and Eukaryotic cells.
II.Prokaryotic cells.
A. Found domains Bacteria and Archaea — prokaryotes.
B. Oldest cells — appeared 3.5 billion years ago.
C. Small — ca. 1/10th the size of an average eukaryotic cell.
D. Simple in terms of structure
E. Structural features of prokaryotic cells.
1. Nucleoid region.
2. Ribosomes.
3. Plasma membrane.
4. Cell wall.
6. Capsule.
7. Prokaryotic flagella.
III. Eukaryotic cells.
A. Animal cells.
B. Plant cells.
C. Major components of all eukaryotic cells.
1. Plasma membrane.
2. Nucleus — membrane-bound organelle containing DNA.
3. Cytoplasm -- organelles suspended in a fluid called cytosol.
IV. Eukaryotic structures.
A. The plasma membrane.
1. Double layer of phospholipids. (See Figure 4.7a)
2. Proteins embedded in the bilayer: the "fluid-mosaic" model (See Figure 4.7b).
3. Functions of membrane proteins: Transport, receptors and enzymes.
4. Plasma membranes are selectively permeable.
B. The nucleus. (See Figure 4.9)
1. Nuclear envelope — the membrane surrounding the nucleus.
2. Chromatin -- DNA and protein.
3. Nucleolus — produces ribosomes.
C. Ribosomes -- the site of protein synthesis.
D. Endoplasmic reticulum (ER). (See Figure 4.11)
1. Rough ER: produces membrane proteins and "secretory proteins."
2. Smooth ER: synthesis of steroids and detoxification.
E. Golgi bodies. (See Figure 4.13)
F. Lysosomes — vesicles containing digestive enzymes.
G. Vacuoles -- membrane-bound sacs (large vesicles).
a. food and contractile vacuoles.
b. central vacuoles in plants.
H. Mitochondrion -- powerhouse of the cell. (See Figure 4.18)
a. site of process cellular respiration.
b. a double membrane — inner membrane has folds called cristae
I. Chloroplast -- found only in plant cells. (See Figure 4.17)
a. Site of photosynthesis = conversion of sunlight energy into chemical energy.
b. Contain stacks of disk-like structures called grana. .
J. Cytoskeleton.
1. Basic unit is the microtubule.
2. Microtubules made up of protein called tubulin.
3. Two special types of microtubules. (See Figure 4.20)
a. Flagella.
b. Cilia.
K. Cell wall.
1. Layer around plasma membranes of plant cells .
2. Contain molecules of cellulose that give the plant cell rigidity.
V. Idealized animal and plant cells. (See Figure 4.6)
NEXT TIME: The Working Cell.