Chapter 4

1. Chapter 4 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 • One circular chromosome, not in a membrane • No histones • No organelles • Peptidoglycan cell walls • Binary fission • Paired chromosomes, in nuclear membrane • Histones • Organelles • Polysaccharide cell walls • Mitotic spindle

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. Flagella arrangement flash animation

11. Figure 4.8

12. Flagella structure flash animation

13. 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)

14. Motile Cells Figure 4.9

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

16. Motility flash animation

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

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

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

20. Figure 4.13b, c

21. 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

22. 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

23. 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

24. Gram-Negative Outer Membrane Figure 4.13c

25. 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

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

27. 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.

28. Plasma Membrane Figure 4.14a

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

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

31. Plasma Membrane • Selective permeability allows passage of some molecules • Enzymes for ATP production • Photosynthetic pigments on foldings called chromatophores or thylakoids

32. Plasma Membrane • Damage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.

33. Movement Across Membranes • Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration. • Facilitative diffusion: Solute combines with a transporter protein in the membrane.

34. Movement Across Membranes Figure 4.17

35. Movement Across Membranes • Osmosis • Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water. • Osmotic pressure • The pressure needed to stop the movement of water across the membrane. Figure 4.18a

36. Figure 4.18c-e

37. Movement Across Membranes • Active transport of substances requires a transporter protein and ATP. • Group translocation of substances requires a transporter protein and PEP.

38. Cytoplasm • Cytoplasm is the substance inside the plasma membrane Figure 4.6a, b

39. Nuclear Area • Nuclear area (nucleoid) Figure 4.6a, b

40. Ribosomes Figure 4.6a

41. Ribosomes Figure 4.19

42. Inclusions • Phosphate reserves • Energy reserves • Energy reserves • Energy reserves • Ribulose 1,5-diphosphate carboxylase for CO2 fixation • Protein covered cylinders • Iron oxide (destroys H2O2) • Metachromatic granules (volutin) • Polysaccharide granules • Lipid inclusions • Sulfur granules • Carboxysomes • Gas vacuoles • Magnetosomes

43. Endospores • Resting cells • Resistant to desiccation, heat, chemicals • Bacillus, Clostridium • Sporulation: Endospore formation • Germination: Return to vegetative state

44. Figure 4.21a

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

46. Figure 4.22a

47. Flagella and Cilia Figure 4.23a, b

48. Microtubules • Tubulin • 9 pairs + 2 arrangements Figure 4.23c

49. Cell Wall • Cell wall • Plants, algae, fungi • Carbohydrates • Cellulose, chitin, glucan, mannan • Glycocalyx • Carbohydrates extending from animal plasma membrane • Bonded to proteins and lipids in membrane

50. Plasma Membrane • Phospholipid bilayer • Peripheral proteins • Integral proteins • Transmembrane proteins • Sterols • Glycocalyx carbohydrates