Chapter 4, part A

1. Chapter 4, part A Functional Anatomy of Prokaryotic and Eukaryotic Cells

2. Prokaryotic Cells • Comparing Prokaryotic and Eukaryotic Cells • Prokaryote comes from the Greek words for prenucleus. • Eukaryote comes from the Greek words for true nucleus.

3. Prokaryote Eukaryote Paired chromosomes, in nuclear membrane Histones Organelles Polysaccharide cell walls Mitotic spindle • One circular chromosome, not in a membrane • No histones • No organelles • Peptidoglycan cell walls • Binary fission

4. Average size: 0.2 -1.0 µm  2 - 8 µm • Basic shapes:

5. Unusual shapes • Star-shaped Stella • Square Haloarcula • Most bacteria are monomorphic • A few are pleomorphic Figure 4.5

6. Arrangements • Pairs: diplococci, diplobacilli • Clusters: staphylococci • Chains: streptococci, streptobacilli

7. Glycocalyx • Outside cell wall • Usually sticky • A capsule is neatly organized • A slime layer is unorganized & loose • Extracellular polysaccharide allows cell to attach • Capsules prevent phagocytosis Figure 4.6a, b

8. Flagella • Outside cell wall • Made of chains of flagellin • Attached to a protein hook • Anchored to the wall and membrane by the basal body Figure 4.8

9. Flagella Arrangement Figure 4.7

10. Figure 4.8

11. Motile Cells • Rotate flagella to run or tumble • Move toward or away from stimuli (taxis) • Flagella proteins are H antigens (e.g., E. coli O157:H7)

12. Motile Cells Figure 4.9

13. Axial Filaments • Endoflagella • In spirochetes • Anchored at one end of a cell • Rotation causes cell to move Figure 4.10a

14. Fimbriae allow attachment to surfaces • Pili are used to transfer DNA from one cell to another Figure 4.11

15. Cell Wall • Prevents osmotic lysis • Made of peptidoglycan (in bacteria) Figure 4.6a, b

16. Peptidoglycan • Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) • Linked by polypeptides Figure 4.13a

17. Figure 4.13b, c

18. Gram-positive cell walls Gram-negative cell walls • Thick peptidoglycan • Teichoic acids • In acid-fast cells, contains mycolic acid • Thin peptidoglycan • No teichoic acids • Outer membrane • LPS • O - polysaccaride • Lipid A

19. Gram-Positive cell walls • Teichoic acids: • Lipoteichoic acid links to plasma membrane • Wall teichoic acid links to peptidoglycan • May regulate movement of cations • Polysaccharides provide antigenic variation Figure 4.13b

20. Gram-Negative Outer Membrane • Lipopolysaccharides, lipoproteins, phospholipids. • Forms the periplasm between the outer membrane and the plasma membrane. • Protection from phagocytes, complement, antibiotics. • O polysaccharide antigen, e.g., E. coli O157:H7. • Lipid A is an endotoxin. • Porins (proteins) form channels through membrane

21. Gram-Negative Outer Membrane Figure 4.13c

22. More on cell wall • Is this Gram negative or positive?

23. Gram Stain Mechanism • Crystal violet-iodine crystals form in cell • Gram-positive • Alcohol dehydrates peptidoglycan • CV-I crystals do not leave • Gram-negative • Alcohol dissolves outer membrane and leaves holes in peptidoglycan • CV-I washes out

24. Atypical Cell Walls • Mycoplasmas • Lack cell walls • Sterols in plasma membrane • Archaea • Wall-less, or • Walls of pseudomurein (lack NAM and D amino acids)

25. Damage to Cell Walls • Lysozyme digests disaccharide in peptidoglycan. • Penicillin inhibits peptide bridges in peptidoglycan. • Protoplast is a wall-less cell. • Spheroplast is a wall-less Gram-positive cell. • L forms are wall-less cells that swell into irregular shapes. • Protoplasts and spheroplasts are susceptible to osmotic lysis.

26. Plasma Membrane Figure 4.14a

27. Plasma Membrane • Phospholipid bilayer • Peripheral proteins • Integral proteins • Transmembrane proteins Figure 4.14b

28. Fluid Mosaic Model • Membrane is as viscous as olive oil. • Proteins move to function • Phospholipids rotate and move laterally Figure 4.14b