Chapter 4 Cell Structure and Function Sections 1-6

1. Chapter 4Cell Structure and FunctionSections 1-6

2. Components of All Cells • Plasma membrane • Controls substances passing in and out of the cell • DNA containing region • Nucleus in eukaryotic cells • Nucleoid region in prokaryotic cells • Cytoplasm • A semifluid mixture containing cell components

3. Organelles • Organelles are structures that carry out special metabolic functions inside a cell • Membrane-enclosed organelles compartmentalize tasks such as building, modifying, and storing substances

4. Prokaryotic and Eukaryotic Cells • Eukaryotic cell • Cell interior is divided into functional compartments, including a nucleus • Prokaryotic cell • Small, simple cells without a nucleus

5. A A prokaryotic cell. plasma membrane cytoplasm DNA nucleus B A eukaryotic (plant) cell. Only eukaryotic cells have a nucleus. Figure 4-2 p54

6. The Cell Theory Emerges • Van Leeuwenhoek was the first to describe small organisms seen through a microscope, which he called animalcules and beasties • Hooke was the first to sketch and name cells • Brown was the first to identify a cell nucleus

7. Cell Theory • The cell theory, a foundation of modern biology, states that cells are the fundamental units of life • In 1839, Schleiden and Schwann proposed the basic concepts of the modern cell theory • All organisms consists of one or more cells • A cell is the smallest unit with the properties of life • Each new cell arises from division of a preexisting cell • Each cell passes its hereditary material to its offspring

8. Take-Home Message:How are all cells alike? • All cells start life with a plasma membrane, cytoplasm, and a region of DNA, which, in eukaryotic cells only, is enclosed by a nucleus • The surface-to-volume ratio limits cell size and influences cell shape • Observations of cells led to the cell theory: All organisms consist of one or more cells; the cell is the smallest unit of life; each new cell arises from another cell; and a cell passes hereditary material to its offspring

9. 4.3 How Do We See Cells? • Most cells are 10–20 micrometers in diameter, about fifty times smaller than the unaided human eye can perceive • One micrometer (μm) is one-thousandth of a millimeter, which is one-thousandth of a meter • We use different types of microscopes to study different aspects of organisms, from the smallest to the largest

10. Table 4-1 p56

11. Different Microscopes, Different Characteristics

12. Relative Sizes human eye (no microscope) largest organisms small animals frog eggs 100 m 10 m 1 m 10 cm 1 cm 1 mm 100 µm

13. Relative Sizes electron microscopes light microscopes most eukaryotic cells viruses most bacteria molecules of life small molecules mitochondria, chloroplasts carbohydrates DNA proteins lipids 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm

14. General Prokaryote Body Plan flagellum 7 plasma membrane capsule pilus cytoplasm, with ribosomes 1 3 5 6 cell wall DNA in nucleoid 2 4

15. Take-Home Message:How are bacteria and archaea alike? • Bacteria and archaea do not have a nucleus. Most kinds have a cell wall around their plasma membrane; the permeable wall reinforces and imparts shape to the cell body • The structure of bacteria and archaea is relatively simple, but as a group these organisms are the most diverse forms of life; they inhabit nearly all regions of the biosphere • Some metabolic processes occur at the plasma membrane of bacteria and archaea; they are similar to complex processes that occur at certain internal membranes of eukaryotic cells

16. 4.5 Introducing Eukaryotic Cells • All protists, fungi, plants, and animals are eukaryotes • Eukaryotic (“true nucleus”) cells carry out much of their metabolism inside membrane-enclosed organelles • Organelle • A structure that carries out a specialized function within a cell

17. Components of Eukaryotic Cells

18. Components of Eukaryotic Cells

19. Cell Wall Central Vacuole Chloroplast nuclear envelope Cytoskeleton nucleolus Nucleus DNA in nucleoplasm microtubules microfilaments intermediate filaments (not shown) Ribosomes Rough ER Mitochondrion Smooth ER Plasmodesma Golgi Body Plasma Membrane Lysosome-Like Vesicle Figure 4-12a p61

20. vacuole cell wall central vacuole plasma membrane chloroplast mitochondrion nucleus B Photosynthetic cell from a blade of timothy grass. Figure 4-11b p60

21. Rough ER Modifies proteins made by ribosomes attached to it Smooth ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins Golgi Body Finishes, sorts, ships lipids, enzymes, and proteins Lysosome Digests, recycles materials Stepped Art p64

22. vacuole plasma membrane mitochondrion nucleus A Human white blood cell. Figure 4-11a p60

23. 4.6 The Nucleus • All of a eukaryotic cell’s DNA is in its nucleus • The nucleus keeps eukaryotic DNA away from potentially damaging reactions in the cytoplasm • The nuclear envelope controls when DNA is accessed

24. Table 4-2 p60

25. nuclear envelope DNA nucleolus nuclear pore nucleoplasm cytoplasm ER Figure 4-13a p62

26. nuclear envelope DNA nucleolus nuclear pore nucleoplasm cytoplasm ER Figure 4-13b p62

27. 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

28. A Condensed Chromosome

29. Take-Home Message:What is the function of the cell nucleus? • A nucleus protects and controls access to a eukaryotic cell’s DNA • The nuclear envelope is a double lipid bilayer. Proteins embedded in it control the passage of molecules between the nucleus and the cytoplasm

30. Chapter 4Cell Structure and FunctionSections 7-12

31. 4.7 The Endomembrane System • Endomembrane system • A series of interacting organelles between the nucleus and the plasma membrane • Makes, modifies, and transports proteins and lipids for secretion or insertion into cell membranes • It also destroys toxins, recycles wastes, and has other specialized functions

32. Rough ER Modifies proteins made by ribosomes attached to it Smooth ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins Golgi Body Finishes, sorts, ships lipids, enzymes, and proteins Lysosome Digests, recycles materials p64

33. 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

34. 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 • Lysosomes • Vesicles containing enzymes that fuse with vacuoles and digest waste materials

35. Vacuoles • Vacuoles • Vesicles with various functions depending on cell type • Many isolate or dispose of waste, debris, and toxins • Central vacuole • Occupies 50 to 90 percent of a cell’s interior • Stores amino acids, sugars, ions, wastes, toxins • Fluid pressure keeps plant cells firm

36. Golgi Bodies • 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

37. Golgi body Smooth ER Plasma membrane 4 5 2 protein in smooth ER Figure 4-15 p65

38. 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

39. 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

40. outer membrane outer compartment inner compartment inner membrane Figure 4-17 p67

41. 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

42. A Photosynthetic cells in a leaf of Plagiomnium ellipticum, a moss. Figure 4-18a p67

43. two outer membranes stroma thylakoids (inner membrane system folded into flattened disks) Figure 4-18b p67

44. Motor Proteins • Motor proteins • Accessory proteins that move molecules through cells on tracks of microtubules and microfilaments • Energized by ATP • Example: kinesins

45. 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

46. pipeline of abutting cell walls primary cell wall plasma membrane cytoplasm secondary cell wall (deposited in layers) primary cell wall middle lamella A Secretions of plant cells form the middle lamella, a layer that cements adjoining cells together. 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. The walls remain after the cells die, and become part of the pipelines that carry water through the plant. Figure 4-22ab p70

47. Cuticle • Cuticle • A type of ECM secreted by cells at a body surface • Plant cuticles consist of waxes and proteins, and help plants retain water and fend off insects • Cuticles of crabs, spiders, and other arthropods is mainly chitin, a polysaccharide

48. Plant Cuticle thick, waxy cuticle at leaf surface outer cell of leaf photosynthetic cell inside leaf

49. Cell Junctions • Cell junctionsallow 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

50. Cell Junctions in Animal Tissues tight junctions