Cell Structure and Function

1. Cell Structure and Function Chapter 4 Part 2

2. 4.7 Visual Summary of Eukaryotic Cells

3. CENTRAL VACUOLE Increases cell surface area; stores metabolic wastes CELL WALL Protects, structurally supports cell CHLOROPLAST Specializes in photosynthesis NUCLEUS nuclear envelope Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA nucleolus DNA in nucleoplasm CYTOSKELETON microtubules Structurally supports, imparts shape to cell; moves cell and its components microfilaments RIBOSOMES intermediate filaments (not shown) (attached to rough ER and free in cytoplasm) Sites of protein synthesis ROUGH ER MITOCHONDRION Modifies proteins made by ribosomes attached to it Energy powerhouse; produces many ATP by aerobic respiration SMOOTH ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins PLASMODESMA Communication junction between adjoining cells GOLGI BODY Finishes, sorts, ships lipids, enzymes, and membrane and secreted proteins PLASMA MEMBRANE Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition LYSOSOME-LIKE VESICLE Digests, recycles materials a Typical plant cell components. Fig. 4-15a, p. 63

4. 4.7 Visual Summary of Eukaryotic Cells

5. NUCLEUS Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA nuclear envelope nucleolus CYTOSKELETON DNA in nucleoplasm Structurally supports, imparts shape to cell; moves cell and its components microtubules microfilaments RIBOSOMES (attached to rough ER and free in cytoplasm) Sites of protein synthesis intermediate filaments MITOCHONDRION Energy powerhouse; produces many ATP by aerobic respiration ROUGH ER Modifies proteins made by ribosomes attached to it CENTRIOLES SMOOTH ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins Special centers that produce and organize microtubules GOLGI BODY PLASMA MEMBRANE Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition Finishes, sorts, ships lipids, enzymes, and membrane and secreted proteins LYSOSOME Digests, recycles materials Fig. 4-15b, p. 63

6. Animation: Common eukaryotic organelles

7. 4.8 The Nucleus • The nucleus keeps eukaryotic DNA away from potentially damaging reactions in the cytoplasm • The nuclear envelope controls when DNA is accessed

8. The Nuclear Envelope • Nuclear envelope • Two lipid bilayers pressed together as a single membrane surrounding the nucleus • Outer bilayer is continuous with the ER • Nuclear pores allow certain substances to pass through the membrane

9. The Nucleoplasm and Nucleolus • Nucleoplasm • Viscous fluid inside the nuclear envelope, similar to cytoplasm • Nucleolus • A dense region in the nucleus where subunits of ribosomes are assembled from proteins and RNA

10. The Chromosomes • Chromatin • All DNA and its associated proteins in the nucleus • Chromosome • A single DNA molecule with its attached proteins • During cell division, chromosomes condense and become visible in micrographs • Human body cells have 46 chromosomes

11. Chromosome Condensation

12. one chromosome (one unduplicated DNA molecule) one chromosome (one duplicated DNA molecule, partially condensed) one chromosome (one duplicated DNA molecule, completely condensed) p. 65

13. 4.9 The Endomembrane System • Endomembrane system • A series of interacting organelles between the nucleus and the plasma membrane • Makes lipids, enzymes, and proteins for secretion or insertion into cell membranes • Other specialized cell functions

14. The Endoplasmic Reticulum • Endoplasmic reticulum (ER) • An extension of the nuclear envelope that forms a continuous, folded compartment • Two kinds of endoplasmic reticulum • Rough ER (with ribosomes) folds polypeptides into their tertiary form • Smooth ER (no ribosomes) makes lipids, breaks down carbohydrates and lipids, detoxifies poisons

15. Vesicles • Vesicles • Small, membrane-enclosed saclike organelles that store or transport substances • Peroxisomes • Vesicles containing enzymes that break down hydrogen peroxide, alcohol, and other toxins • Vacuoles • Vesicles for waste disposal

16. Golgi Bodies and Lysosomes • Golgi body • A folded membrane containing enzymes that finish polypeptides and lipids delivered by the ER • Packages finished products in vesicles that carry them to the plasma membrane or to lysosomes • Lysosomes • Vesicles containing enzymes that fuse with vacuoles and digest waste materials

17. The Endomembrane System

18. The Endomembrane System

19. The Endomembrane System

20. nucleus rough ER smooth ER Golgi body vesicles Fig. 4-18a, p. 66

21. A Nucleus Inside the nucleus, DNA instructions for making proteins are transcribed into RNA, which moves through nuclear pores into the cytoplasm. protein RNA C Vesicles Vesicles that bud from the rough ER carry some of the new proteins to Golgi bodies. Other proteins migrate through the interior of the rough ER, and end up in thesmooth ER. B Rough ER Some of the RNA in the cytoplasm is translated into polypeptide chains by ribosomes attached to the rough ER. The chains enter the rough ER, where they are modified into final form. ribosome attached to ER vesicle budding from ER Fig. 4-18b, p. 66

22. F Plasma membrane Golgi vesicles fuse with the plasma membrane. Lipids and proteins of a vesicle’s membrane fuse with the plasma membrane, and the vesicle’s contents are released to the exterior of the cell. D Smooth ER Some proteins from the rough ER are packaged into new vesicles and shipped to the Golgi. Others become enzymes of the ER, which assemble lipids or inactivate toxins. E Golgi body Proteins arriving in vesicles from the ER are modified into final form and sorted. New vesicles carry them to the plasma membrane or to lysosomes. protein in smooth ER Fig. 4-18c, p. 67

23. Animation: The endomembrane system

24. 4.10 Lysosome Malfunction • When lysosomes do not work properly, some cellular materials are not properly recycled, which can have devastating results • Different kinds of molecules are broken down by different lysosomal enzymes • One lysosomal enzyme breaks down gangliosides, a kind of lipid

25. Tay Sachs Disease • In Tay Sachs disease, a genetic mutation alters the lysosomal enzyme that breaks down gangliosides, which accumulate in nerve cells • Affected children usually die by age five

26. 4.11 Other Organelles • Eukaryotic cells make most of their ATP in mitochondria • Plastids function in storage and photosynthesis in plants and some types of algae

27. Mitochondria • Mitochondrion • Eukaryotic organelle that makes the energy molecule ATP through aerobic respiration • Contains two membranes, forming inner and outer compartments; buildup of hydrogen ions in the outer compartment drives ATP synthesis • Has its own DNA and ribosomes • Resembles bacteria; may have evolved through endosymbiosis

28. Mitochondrion

29. outer membrane outer compartment inner compartment inner membrane 0.5 µm Fig. 4-20, p. 69

30. Plastids • Plastids • Organelles that function in photosynthesis or storage in plants and algae; includes chromoplasts, amyloplasts, and chloroplasts • Chloroplasts • Plastids specialized for photosynthesis • Resemble photosynthetic bacteria; may have evolved by endosymbiosis

31. The Chloroplast

32. two outer membranes stroma thylakoids (inner membrane system folded into flattened disks) Fig. 4-21, p. 69

33. Animation: Structure of a chloroplast

34. The Central Vacuole • Central vacuole • A plant organelle that occupies 50 to 90 percent of a cell’s interior • Stores amino acids, sugars, ions, wastes, toxins • Fluid pressure keeps plant cells firm

35. 4.12 Cell Surface Specializations • A wall or other protective covering often intervenes between a cell’s plasma membrane and the surroundings

36. Eukaryotic Cell Walls • Animal cells do not have walls, but plant cells and many protist and fungal cells do • Primary cell wall • A thin, pliable wall formed by secretion of cellulose into the coating around young plant cells • Secondary cell wall • A strong wall composed of lignin, formed in some plant stems and roots after maturity

37. Plant Cell Walls

38. Fig. 4-22a, p. 70

39. middle lamella plasma membrane cytoplasm A Plant cell secretions form the middle lamella, a layer that cements adjoining cells together. primary cell wall Fig. 4-22a, p. 70

40. Fig. 4-22b, p. 70

41. B In many plant tissues, cells also secrete materials that are deposited in layers on the inner surface of their primary wall. These layers strengthen the wall and maintain its shape. They remain after the cells die, and become part of pipelines that carry water through the plant. secondary cell wall (added in layers) primary cell wall pipeline made of abutting cell walls Fig. 4-22b, p. 70

42. Fig. 4-22c, p. 70

43. middle lamella C Plasmodesmata are channels across the cell walls and the plasma membranes of living cells that are pressed against one another in tissues. plasmodesma middle lamella Fig. 4-22c, p. 70

44. A Plant cell secretions form the middle lamella, a layer that cements adjoining cells together. middle lamella plasma membrane cytoplasm B In many plant tissues, cells also secrete materials that are deposited in layers on the inner surface of their primary wall. These layers strengthen the wall and maintain its shape. They remain after the cells die, and become part of pipelines that carry water through the plant. middle lamella C Plasmodesmata are channels across the cell walls and the plasma membranes of living cells that are pressed against one another in tissues. primary cell wall secondary cell wall (added in layers) plasmodesma primary cell wall middle lamella pipeline made of abutting cell walls Stepped Art Fig. 4-22, p. 70

45. Animation: Plant cell walls

46. Plant Cuticle • Cuticle • A waxy covering that protects exposed surfaces and limits water loss

47. thick, waxy cuticle at leaf surface cell of leaf epidermis photosynthetic cell inside leaf Fig. 4-23, p. 71

48. Matrixes Between Animal Cells • Extracellular matrix (ECM) • A nonliving, complex mixture of fibrous proteins and polysaccharides secreted by and surrounding cells; structure and function varies with the type of tissue • Example: Bone is mostly ECM, composed of collagen (fibrous protein) and hardened by mineral deposits

49. ECM • A bone cell surrounded by extracellular matrix

50. Cell Junctions • Cell junctions allow cells to interact with each other and the environment • In plants, plasmodesmata extend through cell walls to connect the cytoplasm of two cells • Animals have three types of cell junctions: tight junctions, adhering junctions, gap junctions