1. The Cell: An Overview Chapter 5

2. 5.1 Basic Features of Cell Structure and Function  Cells are small and are visualized using a microscope  Cells have a DNA-containing central region surrounded by cytoplasm  Cells occur in prokaryotic an eukaryotic forms, each with distinctive structures and organization

3. Microscopes and Cells  Robert Hooke and Anton van Leeuwenhoek  Robert Brown  Mattias Schleiden and Theodore Schwann  Rudolf Virchow

4. Microscopes and Cells Fig. 5-1, p. 92

5. Cell Theory: Fundamental to Life  All organisms are cellular  Cell: the smallest unit of life  Cells come only from preexisting cells

6. Examples of Cells Fig. 5-2, p. 92

7. Units of Measure Fig. 5-3, p. 93

8. Research Methods Fig. 5-4, p. 94

9. Cells are Small  No life is smaller than an intact cell Diffusion and surface area to volume ratios  Cells viewed with microscopes Light and electron  Magnification and resolution limit microscopes

10. Surface to Volume Ratios

11. All Cells Contain DNA  All cells have a central region with DNA Stores hereditary information (connection to evolution) Genes are located on DNA Proteins replicate DNA and copy information to RNA

12. Cytoplasm  Cytoplasm Surrounds the central region  Cytosol Aqueous solution of cell  Organelles Small organized structures within cytosol

13. Plasma Membrane Fig. 5-6, p. 95

14. Plasma Membrane  Plasma membrane defines cytoplasm  Lipid bilayer and proteins  Hydrophobic Selective passage hydrophilic  Internal environment of cell different from external

15. Prokaryotes and Eukaryotes  Prokaryotes No boundary membrane in central region Nucleoid Domains: Archaea and Bacteria  Eukaryotes Boundary membrane in central region True nucleus Domain: Eukarya

16. Components of Prokaryotic and Eukaryotic Cells Table 5-1, p. 96

17. 5.2 Prokaryotic Cells  Prokaryotic cells have little or no internal membrane structure

18. Prokaryotic Cell Structure Fig. 5-7, p. 97

19. Prokaryotic Internal Structure  Small, little to no membrane structure Cell wall & capsule  Plasma membrane allows metabolism ATP in mitochondria and chloroplasts Evolution by endosymbiosis

20. 5.3 Eukaryotic Cells  Eukaryotic cells have a membrane-enclosed nucleus and cytoplasmic organelles  Nucleus contains much more DNA than the prokaryotic nucleoid  Cytoplasm has endomembrane systems dividing cell into functional and structural components

21. 5.3 (cont.)  Mitochondria are the powerhouses of the cell  Microbodies carry out vital reactions that link metabolic pathways  The cytoskeleton supports and moves cell structures  Flagella and cilia are the propellers of eukaryotic cells

22. Eukaryotic Cell Overview  Domain Eukarya (true nucleus) Includes protists, fungi, plants and animals  Eukaryotic plasma membrane function Regulate/recognize substances (immune system) Cell-to-cell binding  Fungi, plants and many protists have cell walls

23. Typical Animal Cell Fig. 5-8a, p. 99

24. Typical Plant Cell Fig. 5-9a, p. 100

25. Eukaryotic Nucleus  Nuclear envelope separates nucleus and cytoplasm Two membranes and nuclear pores  Nucleoplasm within nuclear envelope Chromatin and chromosomes  Nucleolus Genes for ribosomal RNA

26. Nuclear Envelope Fig. 5-10, p. 101

27. Endomembrane System  Endomembrane system Connects all membranes Synthesizes/ modifies membrane proteins Synthesizes lipids Detoxification  Vesicles exchange membrane throughout endomembrane system ER, Golgi, nuclear envelope, lysosomes, vesicles, plasma membrane

28. Endoplasmic Reticulum Fig. 5-11, p. 102

29. Endoplasmic Reticulum  Endoplasmic reticulum (ER) Interconnected network of membrane with cisternae and lumen  Rough ER Ribosomes bound to surface Membrane-associated protein synthesis

30. Endoplasmic Reticulum  Smooth ER No ribosomes Synthesizes lipids and detoxifies  Proportion rough/smooth ER reflect cell activities

31. Golgi Complex Fig. 5-12, p. 103

32. Lysosomes  Lysosomes Vesicles from Golgi complex Hydrolytic enzymes from ER; low pH  Autophagy removes nonfunctional organelles  Phagocytosis digests extracellular material Major function of immune systems

33. Endocytosis, Exocytosis and Lysosomes Fig. 5-13-14, p. 104

34. Vesicle Traffic Fig. 5-15, p. 105

35. Mitochondria  Cellular respiration yields ATP  Mitochondria have two membranes Outer membrane smooth Inner membrane folded (cristae) Mitochondrial matrix  Mitochondria have own genome Endosymbiosis

36. Mitochondria Fig. 5-16, p. 106

37. Microbodies  Microbodies Single membrane organelles Not part of endomembrane system  Microbody enzymes link biochemical pathways  Examples Peroxisomes, glyoxysomes or glycosomes

38. Microbodies Fig. 5-17, p. 107

39. Cytoskeleton  Cytoskeleton Maintains shape and organization Interconnected protein fibers and tubes  Most prominent in animal cells Plants and fungi also use cell walls and central vacuole

40. Cytoskeleton Examples Fig. 5-18, p. 107

41. Cytoskeleton Components  Main elements of animal cytoskeletons Microtubules are supportive Intermediate fibers thinner, interconnected with microtubules Microfilaments thinnest

42. Cytoskeleton Components  Each element assembled from proteins Microtubules from tubulin Intermediate fibers from intermediate filaments Microfilaments from actins

43. Major Components of Cytoskeleton Fig. 5-19, p. 108

44. Microtubules  Many microtubules originate from centrosome Originate from centrioles Anchor major organelles Microtubules provide tracks for mobile organelles

45. Microtubules  Organelle movement by motor proteins Vesicle attached to motor protein “walks” along microtubule Requires ATP  Cytoskeleton allows large cellular movement Amoeboid motion, cytoplasmic streaming, cell division

46. Kinesin Fig. 5-20a,b, p. 108

47. Flagella and Cilia  Flagella and cilia for cell motion Identical structure; cilia shorter/greater in number  Structures are 9+2 Motor proteins From centrioles and basal body  Prokaryotes have analogous (not homologous) flagella and cilia

48. Flagellar Structure Fig. 5-21, p. 109

49. Flagellar and Ciliary Beating Patterns Fig. 5-22, p. 110

50. Centrioles Fig. 5-23, p. 110

51. 5.4 Specialized Structures of Plant Cells  Chloroplasts are biochemical factories powered by sunlight  Central vacuoles have diverse roles in storage, structural support, and cell growth  Cell walls support and protect plant cells

52. Chloroplasts  Chloroplasts have multiple membranes for photosynthesis Outer smooth, inner folded; stroma inside both Thylakoids and grana inside stroma Endosymbiosis  Plastids are plant organelles that include chloroplasts, amlyoplasts and chromoplasts

53. Plastids  Plant organelles including Chloroplasts Amyloplasts Chromoplasts

54. Chloroplast Structure Fig. 5-24, p. 111

55. Central Vacuoles  Central vacuoles Large vesicles in plants 90% of many plant cell’s volume Turgor pressure from water Other functions  Tonoplast Membrane surrounding central vacuole

56. Cell Walls  Cell walls Extracellular structures Provide structure and contain pressure Cellulose fibers for tensile strength, other organic molecules for compression resistance  Two types of cells walls Primary Secondary

57. Cell Walls  Middle lamella holds adjacent cell walls together  Plasmodesmata provide cellular connections No cell wall passage

58. Cell Wall Structure Fig. 5-25, p. 112

59. 5.5 The Animal Cell Surface  Cell adhesion molecules organize animal cells into tissues and organs  Cell junctions reinforce cell adhesions and provide avenues of communication  The extracellular matrix organizes the cell exterior

60. Cell Adhesion and Junctions  Cell adhesion molecules bind cells together nonpermanently Glycoproteins bind to specific molecules on other cells  Cell junctions seal spaces between cells permanently Direct cellular communication

61. Functions of Cellular Junction  Anchoring junctions “weld” cells together Desmosomes and adherens  Tight junctions prevent small ion movement Seal spaces and fuse membranes  Gap junctions allow passage without membrane control Same tissue

62. Animal Cell Connections Fig. 5-26, p. 114

63. Extracellular Matrix  Collagen proteins Tensile strength and elasticity  Proteoglycans Interlinkage Changes consistency (jellylike to hard and elastic)  Fibronectins Connect cells via integrins

64. Extracellular Matrix Fig. 5-27, p. 115

65. Animation: Fluid mosaic model PLAY ANIMATION