Chapter 3

1. Chapter 3 Cell Structure and Function

2. Processes of Life • Growth • Reproduction • Responsiveness • Metabolism

3. Examples of types of cells Figure 3.1

4. Prokaryotic and Eukaryotic Cells: An Overview • Prokaryotes • Lack nucleus • Lack various internal structures bound with phospholipid membranes • Are small, ~1.0 µm in diameter • Have a simple structure • Composed of bacteria and archaea

5. Typical prokaryotic cell Figure 3.2

6. Prokaryotic and Eukaryotic Cells: An Overview • Eukaryotes • Have nucleus • Have internal membrane-bound organelles • Are larger, 10–100 µm in diameter • Have more complex structure • Composed of algae, protozoa, fungi, animals, and plants

7. Typical eukaryotic cell Figure 3.3

8. Approximate size of various types of cells Figure 3.4

9. External Structures of Bacterial Cells • Glycocalyces • Gelatinous, sticky substance surrounding the outside of the cell • Composed of polysaccharides, polypeptides, or both

10. External Structures of Bacterial Cells • Two Types of Glycocalyces • Capsule • Composed of organized repeating units of organic chemicals • Firmly attached to cell surface • May prevent bacteria from being recognized by host • Slime layer • Loosely attached to cell surface • Water soluble • Sticky layer allows prokaryotes to attach to surfaces

11. Glycocalyces Figure 3.5

12. External Structures of Bacterial Cells Animation: Motility

13. External Structures of Bacterial Cells • Flagella • Are responsible for movement • Have long structures that extend beyond cell surface • Are not present on all bacteria

14. External Structures of Bacterial Cells • Flagella • Structure • Composed of filament, hook, and basal body • Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins

15. External Structures of Prokaryotic Cells Animation: Flagella: Structure

16. Proximal structure of bacterial flagella Figure 3.6

17. Basic arrangements of bacterial flagella Figure 3.7

18. External Structures of Bacterial Cells Animation: Flagella: Arrangement

19. External Structures of Bacterial Cells Animation: Flagella: Spirochetes

20. Axial filament Figure 3.8

21. External Structures of Bacterial Cells • Flagella • Function • Rotation propels bacterium through environment • Rotation reversible; can be counterclockwise or clockwise • Bacteria move in response to stimuli (taxis) • Runs • Tumbles

22. Motion of a peritrichous bacterium Figure 3.9

23. External Structures of Bacterial Cells Animation: Flagella: Movement

24. External Structures of Bacterial Cells • Fimbriae and Pili • Rod-like proteinaceous extensions

25. External Structures of Bacterial Cells • Fimbriae • Sticky, bristlelike projections • Used by bacteria to adhere to one another, to hosts, and to substances in environment • Shorter than flagella • Serve an important function in biofilms

26. Fimbriae Figure 3.10

27. External Structures of Prokaryotic Cells • Pili • Tubules composed of pilin • Also known as conjugation pili • Longer than fimbriae but shorter than flagella • Bacteria typically only have one or two per cell • Mediate the transfer of DNA from one cell to another (conjugation)

28. Pilus Figure 3.11

29. Bacterial Cell Walls • Provide structure and shape and protect cell from osmotic forces • Assist some cells in attaching to other cells or in resisting antimicrobial drugs • Can target cell wall of bacteria with antibiotics • Give bacterial cells characteristic shapes • Composed of peptidoglycan • Scientists describe two basic types of bacterial cell walls • Gram-positive and Gram-negative

30. Bacterial shapes and arrangements Figure 3.12

31. Comparison of structures of glucose, NAG, and NAM Figure 3.13

32. Bacterial Cell Walls • Gram-positive Bacterial Cell Walls • Relatively thick layer of peptidoglycan • Contain unique polyalcohols called teichoic acids • Appear purple following Gram staining procedure • Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation

33. Gram-positive bacteria Figure 3.15a

34. Prokaryotic Cell Walls • Gram-Negative Bacterial Cell Walls • Have only a thin layer of peptidoglycan • Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) • May be impediment to the treatment of disease • Appear pink following Gram staining procedure

35. Gram-negative bacteria Figure 3.15b

36. Bacterial Cytoplasmic Membranes • Structure • Referred to as phospholipid bilayer • Composed of lipids and associated proteins • Fluid mosaic model describes current understanding of membrane structure

37. Structure of prokaryotic cytoplasmic membrane Figure 3.16

38. Bacterial Cytoplasmic Membranes • Function • Energy storage • Harvest light energy in photosynthetic bacteria • Selectively permeable • Naturally impermeable to most substances • Proteins allow substances to cross membrane • Maintain concentration and electrical gradient

39. Electrical potential of a cytoplasmic membrane Figure 3.17

40. Bacterial Cytoplasmic Membranes • Function • Passive processes • Diffusion • Facilitated diffusion • Osmosis

41. Passive processes of movement Figure 3.18

42. Osmosis Figure 3.19

43. Effects of solutions on cells Figure 3.20

44. Prokaryotic Cytoplasmic Membranes • Function • Active processes • Active transport • Group translocation • Substance chemically modified during transport

45. Mechanisms of active transport Figure 3.21

46. Bacterial Cytoplasmic Membranes Animation: Active Transport: Overview

47. Bacterial Cytoplasmic Membranes Animation: Active Transport: Types

48. Group translocation Figure 3.22

49. Cytoplasm of Bacteria • Cytosol • Liquid portion of cytoplasm • Inclusions • May include reserve deposits of chemicals • Endospores • Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions

50. The formation of an endospore Figure 3.24