1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 4 A Tour of the Cell

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Art of Looking at Cells Artists have long found inspiration in the visual richness of the living world Conversely, scientists use art to illuminate their findings – Micrographs show structures as scientists see them – Drawings can emphasize details

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings INTRODUCTION TO THE CELL 4.1 Microscopes provide windows to the world of the cell A light microscope (LM) enables us to see the overall shape and structure of a cell – Passes visible light through a specimen – Can study living cells and cells and tissues that have been stained – Can magnify only about 1,000 times Video: Euglena Video: Euglena

5. LE 4-1a Eyepiece Ocular lens Objective lens Specimen Condenser lens Light source

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Magnification is the increase in the apparent size of an object; for example, 1,000X

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Resolution is a measure of the clarity of an image – A light microscope can resolve objects as small as 2  m

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The electron microscope (EM) allows greater magnification than LM and reveals cellular details – Uses a beam of electrons rather than light – Has much greater resolution than LM (2 nm) – Can magnify up to 100,000 times – Cannot be used with living specimens

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Scanning electron microscope (SEM) studies detailed architecture of cell surfaces

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transmission electron microscope (TEM) studies the details of internal cell structure

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Modifications to LM use different techniques to enhance contrast and selectively highlight cellular components

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.2 Most cells are microscopic Cells vary in size and shape – Minimum is determined by the total size of all the molecules required for cellular activity – Maximum is limited by the need for sufficient surface area to carry out functions

19. LE 4-2a Human height Length of some nerve and muscle cells Chicken egg Frog egg Most plant and animal cells Nucleus Most bacteria Mitochondrion Mycoplasmas (smallest bacteria) Ribosome Viruses Proteins Lipids Small molecules Atoms Unaided eye Light microscope Electron microscope

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A small cell has a greater ratio of surface area to volume than a large cell of the same shape The microscopic size of most cells ensures a sufficient surface area across which nutrients and wastes can move to service the cell

21. LE 4-2b 30  m 10  m 30  m Surface area of one large cube = 5,400  m 2 Total surface area of 27 small cubes = 16,200  m 2

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells There are two kinds of cells – Prokaryotic (bacteria, archaea) – Eukaryotic (protists, plants, fungi, animals) All cells share some common features – Plasma membrane – DNA – ribosomes

23. LE 4-3a Nucleoid region Prokaryotic cell Nucleus Colorized TEM 15,000  Eukaryotic cell Organelles

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells – Usually relatively small, relatively simple cells Do not have a membrane-bound nucleus DNA is coiled into a nucleoid region in the cytoplasm Cytoplasm includes ribosomes

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other prokaryotic structures – Plasma membrane – Complex cell wall – Capsule, pili, prokaryotic flagella in some forms

26. LE 4-3b Prokaryotic flagella Ribosomes Capsule Cell wall Plasma membrane Nucleoid region (DNA) Pili

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.4 Eukaryotic cells are partitioned into functional compartments Eukaryotic cells are usually larger than prokaryotic cells (10-100 (  m diameter) – Distinguished by a true nucleus – Contain both membranous and nonmembranous organelles Compartmentalize metabolism Increase membrane surface area for reactions

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal cells – Are bounded by the plasma membrane alone – Lack a cell wall – Contain centrioles and lysosomes – Often have flagella Video: Cytoplasmic Streaming Video: Cytoplasmic Streaming

29. LE 4-4a Rough endoplasmic reticulum Smooth endoplasmic reticulum Nucleus Flagellum Lycosome Centriole Not in most plant cells Peroxisome Microtubule Intermediate filament Microfilament Cytoskeleton Golgi apparatus Ribosomes Plasma membrane Mitochondrion

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plant cells – Are bounded by both a plasma membrane and a rigid cellulose cell wall – Have a central vacuole and chloroplasts – Usually lack centrioles, lysosomes, and flagella

31. LE 4-4b Not in animal cells Golgi apparatus Nucleus Central vacuole Chloroplast Cell wall Mitochondrion Peroxisome Plasma membrane Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Microtubule Intermediate filament Microfilament Cytoskeleton

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ORGANELLES OF THE ENDOMEMBRANE SYSTEM 4.5 The nucleus is the cell's genetic control center The nucleus contains the cell's DNA – Controls cellular activities by directing protein synthesis – Forms long fibers of chromatin that make up chromosomes

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The nucleus is separated from the cytoplasm by the nuclear envelope – Pores in the envelope control flow of materials in and out – Ribosomes are synthesized in the nucleolus

34. LE 4-5 Chromatin Nucleolus Pore Nucleus Two membranes of nuclear envelope Rough endoplasmic reticulum Ribosomes

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.6 Overview: Many cell organelles are connected through the endomembrane system The endomembrane system is a collection of membranous organelles – Divide the cell into compartments – Work together in the synthesis, storage, and export of molecules Prime example: Endoplasmic reticulum (ER) – A continuous network of flattened sacs and tubes

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.7 Smooth endoplasmic reticulum has a variety of functions Smooth endoplasmic reticulum (smooth ER) lacks attached ribosomes – Synthesizes lipids – Processes materials such as toxins and drugs in liver cells – Stores and releases calcium ions in muscle cells

37. LE 4-7 Smooth ER Rough ER Nuclear envelope Ribosomes Smooth ER Rough ER TEM 45,000 

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.8 Rough endoplasmic reticulum makes membrane and proteins Rough endoplasmic reticulum (rough ER) is studded with ribosomes – Manufactures membranes – Modifies and packages proteins that will be Transported to other organelles Secreted by the cell

39. LE 4-8 Transport vesicle buds off Ribosome Polypeptide Glycoprotein Sugar chain Rough ER Secretary (glyco-) protein inside trans- port vesicle

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.9 The Golgi apparatus finishes, sorts, and ships cell products The Golgi apparatus consists of stacks of flattened membranous sacs – Receives and modifies substances manufactured by ER – Ships modified products to other organelles or the cell surface

41. LE 4-9 Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming “Shipping” side of Golgi apparatus Transport vesicle from the Golgi Golgi apparatus TEM 130,000 

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.10 Lysosomes are digestive compartments within a cell Lysosomes are sacs of enzymes that form from the Golgi apparatus – Function in digestion within a cell – Destroy bacteria that have been ingested into white blood cells – Recycle damaged organelles Animation: Lysosome Formation Animation: Lysosome Formation

43. LE 4-10a Plasma membrane Rough ER Lysosomes Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus Engulfment of particle “Food” Food vacuole Digestion Lysosome engulfing damaged organelle

44. LE 4-10b Lysosome Nucleus TEM 8,500 

45. LE 4-10c Lysosome containing two damaged organelles TEM 42,500  Mitochondrion fragment Peroxisome fragment

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 4.11 Abnormal lysosomes can cause fatal diseases Lysosomal storage diseases – Result from an inherited lack of one or more lysosomal enzymes – Seriously interfere with various cellular functions

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.12 Vacuoles function in the general maintenance of the cell Plant cells contain a large central vacuole – Has lysosomal and storage functions Some protists have contractile vacuoles – Pump excess water out of cell Video: Chlamydomonas Video: Chlamydomonas Video: Paramecium Vacuole Video: Paramecium Vacuole

48. LE 4-12a Central vacuole Nucleus Chloroplast Colorized TEM 8,700 

49. LE 4-12b Nucleus LM 650  Contractile vacuoles

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.13 A review of the endomembrane system The various organelles of the endomembrane system are interconnected structurally and functionally Animation: Endomembrane System Animation: Endomembrane System

51. LE 4-13 Transport vesicle from ER to Golgi Rough ER Nucleus Smooth ER Nuclear envelope Golgi apparatus Lysosome Vacuole Plasma membrane Transport vesicle from Golgi to plasma membrane

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ENERGY-CONVERTING ORGANELLES 4.14 Chloroplasts convert solar energy to chemical energy Chloroplasts are found in plants and some protists – Are the site of photosynthesis – Have a complex membranous structure for capturing and converting light energy

53. LE 4-14 Chloroplast Stroma Inner and outer membranes Granum Intermembrane space TEM 9,750 

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.15 Mitochondria harvest chemical energy from food Mitochondria are found in nearly all eukaryotic cells – Divided into two membranous compartments Intermembrane space Second compartment enclosed by inner membrane – Contains fluid mitochondrial matrix – Membrane folded into cristae

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Carry out cellular respiration Convert the chemical energy in food to ATP for cellular work

56. LE 4-15 Mitochondrion Intermembrane space Outer membrane Inner membrane Cristae Matrix TEM 44,880 

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings THE CYTOSKELETON AND RELATED STRUCTURES 4.16 The cell's internal skeleton helps organize its structure and activities The cytoskeleton is network of three types of protein fibers – Microfilaments Rods of globular proteins Enable cells to change shape and move

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Intermediate filaments Ropes of fibrous proteins Reinforce the cell and anchor certain organelles – Microtubules Hollow tubes of globular proteins Give the cell rigidity Anchor organelles and act as tracks for organelle movement

59. LE 4-16 Actin subunit Fibrous subunit 7 nm Microfilament Intermediate filament 10 nm Tubulin subunit Microtubule 25 nm

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4.17 Cilia and flagella move when microtubules bend Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells – Move whole cells or materials across the cell surface Video: Paramecium Cilia Video: Paramecium Cilia Animation: Cilia and Flagella Animation: Cilia and Flagella

63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The structure and mechanism of cilia and flagella are similar – Microtubules wrapped in an extension of the plasma membrane 9 + 2 arrangement Extend into basal bodies Movement of dynein arms produces microtubule bending

64. LE 4-17c Outer microtubule doublet Central microtubules Radial spoke Dynein arms Plasma membrane Flagellum Electron micrographs of cross sections: Flagellum Basal body TEM 206,500  Basal body (structurally identical to centriole) TEM 206,500 

65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CELL SURFACES AND JUNCTIONS 4.18 Cell surfaces protect, support, and join cells Cells interact with their environments and each other via their surfaces Many cells are protected by more than the plasma membrane

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plant cell walls – Made largely of cellulose – Provide protection and support – Connect by plasmodesmata, channels through the wall

67. LE 4-18a Vacuole Walls of two adjacent plant cells Plasmodesmata Layers of one plant cell wall Cytoplasm Plasma membrane

68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal cells – Embedded in an extracellular matrix that binds cells together in tissues – Connect by cell junctions Tight junctions bind cells into leakproof sheets Anchoring junctions link cells into strong tissues Gap junctions allow substances to flow from cell to cell

69. LE 4-18b Tight junctions Anchoring junction Gap junctions Extracellular matrix Space between cells Plasma membranes of adjacent cells

70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Tight Junctions Animation: Tight Junctions Animation: Desmosomes Animation: Desmosomes Animation: Gap Junctions Animation: Gap Junctions

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings FUNCTIONAL CATEGORIES OF ORGANELLES 4.19 Eukaryotic organelles comprise four functional categories Eukaryotic organelles fall into four functional categories that work together to produce the cell's emergent properties – Manufacturing – Breakdown – Energy processing – Support, movement, and communication between cells