1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 6 A Tour of the Cell

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START Match the molecule with type. 1.GlycogenA. Carbohydrate 2.CholestrolB. Lipid 3.RNAC. Protein 4.CollagenD. Nucleic Acid 5.Hemoglobin 6.A gene 7.Triacylglycerol 8.Enzyme 9.Cellulose 10.Chitin

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings WORD ROOTS Centro-plasm- -Soma-desma Chloro-pro- Cili-pseudo- Cyto--pod -ellthylaco- Endo-tono- Extra-trans- Flagell--port

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings WORD ROOTS CONTINUED Glyco-tono- Lamin--plast Lyso-trans- Micro--port Nucle-ultra- -oidvacu- Phago- -kytos

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The Importance of Cells All organisms are made of cells The cell is the simplest collection of matter that can live Cell structure is correlated to cellular function All cells are related by their descent from earlier cells

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

7. Concept 6.1: To study cells, biologists use microscopes and the tools of biochemistry Though usually too small to be seen by the unaided eye, cells can be complex

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microscopy Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image The minimum resolution of an LM is about 200 nanometers (nm), the size of a small bacterium

9. LE 6-2 Measurements 1 centimeter (cm) = 10 –2 meter (m) = 0.4 inch 1 millimeter (mm) = 10 –3 m 1 micrometer (µm) = 10 –3 mm = 10 –6 m 1 nanometer (nm) = 10 –3 µm = 10 –9 m 10 m 1 m Human height Length of some nerve and muscle cells Chicken egg 0.1 m 1 cm Frog egg 1 mm 100 µm Most plant and animal cells 10 µm Nucleus 1 µm Most bacteria Mitochondrion Smallest bacteria Viruses 100 nm 10 nm Ribosomes Proteins Lipids 1 nm Small molecules Atoms 0.1 nm Unaided eye Light microscope Electron microscope

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LMs can magnify effectively to about 1,000 times the size of the actual specimen Various techniques enhance contrast and enable cell components to be stained or labeled Most subcellular structures, or organelles, are too small to be resolved by a LM

11. LE 6-3a Brightfield (unstained specimen) 50 µm Brightfield (stained specimen) Phase-contrast

12. LE 6-3b 50 µm Confocal Differential- interference- contrast (Nomarski) Fluorescence

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two basic types of electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3D Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen TEMs are used mainly to study the internal ultrastructure of cells

14. LE 6-4 1 µm Scanning electron microscopy (SEM) Cilia Longitudinal section of cilium Transmission electron microscopy (TEM) Cross section of cilium

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Isolating Organelles by Cell Fractionation Cell fractionation takes cells apart and separates the major organelles from one another Ultracentrifuges fractionate cells into their component parts Cell fractionation enables scientists to determine the functions of organelles

16. LE 6-5a Homogenization Homogenate Tissue cells Differential centrifugation

17. LE 6-5b Pellet rich in nuclei and cellular debris Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes 150,000 g 3 hr 80,000 g 60 min 20,000 g 20 min 1000 g (1000 times the force of gravity) 10 min Supernatant poured into next tube

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START 1. Define Cytology 2. What do cell biologists use TEM to study? 3. What does an SEM show best? 4. What advantages does light microscopy have over TEM and SEM?

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists, fungi, animals, and plants all consist of eukaryotic cells

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparing Prokaryotic and Eukaryotic Cells Basic features of all cells: – Plasma membrane – Semifluid substance called the cytosol – Chromosomes (carry genes) – Ribosomes (make proteins)

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells have no nucleus In a prokaryotic cell, DNA is in an unbound region called the nucleoid Prokaryotic cells lack membrane-bound organelles

22. LE 6-6 A typical rod-shaped bacterium A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm Pili Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cells have DNA in a nucleus that is bounded by a membranous nuclear envelope Eukaryotic cells have membrane-bound organelles Eukaryotic cells are generally much larger than prokaryotic cells The logistics of carrying out cellular metabolism sets limits on the size of cells

24. LE 6-7 Total surface area (height x width x number of sides x number of boxes) 6 125 150 750 1 1 1 5 1.2 6 6 Total volume (height x width x length X number of boxes) Surface-to-volume ratio (surface area  volume) Surface area increases while Total volume remains constant

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of the cell The general structure of a biological membrane is a double layer of phospholipids

26. LE 6-8 Hydrophilic region Hydrophobic region Carbohydrate side chain Structure of the plasma membrane Hydrophilic region Phospholipid Proteins Outside of cell Inside of cell 0.1 µm TEM of a plasma membrane

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Panoramic View of the Eukaryotic Cell A eukaryotic cell has internal membranes that partition the cell into organelles Plant and animal cells have most of the same organelles

28. LE 6-9a Flagellum Centrosome CYTOSKELETON Microfilaments Intermediate filaments Microtubules Peroxisome Microvilli ENDOPLASMIC RETICULUM (ER Rough ER Smooth ER Mitochondrion Lysosome Golgi apparatus Ribosomes: Plasma membrane Nuclear envelope NUCLEUS In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Nucleolus Chromatin

29. LE 6-9b Rough endoplasmic reticulum In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata Smooth endoplasmic reticulum Ribosomes (small brown dots) Central vacuole Microfilaments Intermediate filaments Microtubules CYTOSKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Nuclear envelope Nucleolus Chromatin NUCLEUS Centrosome Golgi apparatus Mitochondrion Peroxisome Plasma membrane

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START 1. If an eukaryote has a diameter that is 10 times that of a bacterial cell, proportionally how much more surface area would a eukaryote cell have? 2. Proportionally how much more volume would it have?

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.3: The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Nucleus: Genetic Library of the Cell The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separating it from the cytoplasm

33. LE 6-10 Close-up of nuclear envelope Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Ribosome Pore complexes (TEM)Nuclear lamina (TEM) 1 µm Rough ER Nucleus 1 µm 0.25 µm Surface of nuclear envelope

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes: Protein Factories in the Cell Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations: – In the cytosol (free ribosomes) – On the outside of the endoplasmic reticulum (ER) or the nuclear envelope (bound ribosomes)

35. LE 6-11 Ribosomes 0.5 µm ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START 1. How does the nucleus control protein synthesis in the cytoplasm? 2. What is the difference between a free ribosome and a bound ribosome?

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane These components are either continuous or connected via transfer by vesicles

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER: – Smooth ER, which lacks ribosomes – Rough ER, with ribosomes studding its surface

39. LE 6-12 Ribosomes Smooth ER Rough ER ER lumen Cisternae Transport vesicle Smooth ER Rough ER Transitional ER 200 nm Nuclear envelope

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Functions of Smooth ER The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Stores calcium – Detoxifies poison

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Functions of Rough ER The rough ER – Has bound ribosomes – Produces proteins and membranes, which are distributed by transport vesicles – Is a membrane factory for the cell

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Golgi apparatus consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus: – Modifies products of the ER – Manufactures certain macromolecules – Sorts and packages materials into transport vesicles The Golgi Apparatus: Shipping and Receiving Center

43. LE 6-13 trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm Golgi apparatus cis face (“receiving” side of Golgi apparatus) Vesicles coalesce to form new cis Golgi cisternae Vesicles also transport certain proteins back to ER Vesicles move from ER to Golgi Vesicles transport specific proteins backward to newer Golgi cisternae Cisternal maturation: Golgi cisternae move in a cis- to-trans direction Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma mem- brane for secretion Cisternae

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomes also use enzymes to recycle organelles and macromolecules, a process called autophagy Animation: Lysosome Formation Animation: Lysosome Formation

45. LE 6-14a Phagocytosis: lysosome digesting food 1 µm Plasma membrane Food vacuole Lysosome Nucleus Digestive enzymes Digestion Lysosome Lysosome contains active hydrolytic enzymes Food vacuole fuses with lysosome Hydrolytic enzymes digest food particles

46. LE 6-14b Autophagy: lysosome breaking down damaged organelle 1 µm Vesicle containing damaged mitochondrion Mitochondrion fragment Lysosome containing two damaged organelles Digestion Lysosome Lysosome fuses with vesicle containing damaged organelle Peroxisome fragment Hydrolytic enzymes digest organelle components

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vacuoles: Diverse Maintenance Compartments Vesicles and vacuoles (larger versions of vacuoles) are membrane-bound sacs with varied functions A plant cell or fungal cell may have one or several vacuoles

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water Video: Paramecium Vacuole Video: Paramecium Vacuole

49. LE 6-15 5 µm Central vacuole Cytosol Tonoplast Central vacuole Nucleus Cell wall Chloroplast

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Endomembrane System: A Review The endomembrane system is a complex and dynamic player in the cell’s compartmental organization Animation: Endomembrane System Animation: Endomembrane System

51. LE 6-16-1 Nuclear envelope Nucleus Rough ER Smooth ER

52. LE 6-16-2 Nuclear envelope Nucleus Rough ER Smooth ER Transport vesicle cis Golgi trans Golgi

53. LE 6-16-3 Nuclear envelope Nucleus Rough ER Smooth ER Transport vesicle cis Golgi trans Golgi Plasma membrane

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START: Name the components and functions. A B C D E F D G

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.5: Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration Chloroplasts, found only in plants and algae, are the sites of photosynthesis Mitochondria and chloroplasts are not part of the endomembrane system Peroxisomes are oxidative organelles

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP

57. LE 6-17 Mitochondrion Intermembrane space Outer membrane Inner membrane Cristae Matrix 100 nm Mitochondrial DNA Free ribosomes in the mitochondrial matrix

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts: Capture of Light Energy The chloroplast is a member of a family of organelles called plastids Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae Chloroplast structure includes: – Thylakoids, membranous sacs – Stroma, the internal fluid

59. LE 6-18 Chloroplast DNA Ribosomes Stroma Inner and outer membranes Granum Thylakoid 1 µm

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Peroxisomes: Oxidation Peroxisomes are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water

61. LE 6-19 Chloroplast Peroxisome Mitochondrion 1 µm

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles It is composed of three types of molecular structures: – Microtubules – Microfilaments – Intermediate filaments

63. LE 6-20 Microtubule Microfilaments 0.25 µm

64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Roles of the Cytoskeleton: Support, Motility, and Regulation The cytoskeleton helps to support the cell and maintain its shape It interacts with motor proteins to produce motility Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton Recent evidence suggests that the cytoskeleton may help regulate biochemical activities

65. LE 6-21a Vesicle Receptor for motor protein Microtubule of cytoskeleton Motor protein (ATP powered) ATP

66. LE 6-21b 0.25 µm Microtubule Vesicles

67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Components of the Cytoskeleton Microtubules are the thickest of the three components of the cytoskeleton Microfilaments, also called actin filaments, are the thinnest components Intermediate filaments are fibers with diameters in a middle range

68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

71. Microtubules Microtubules are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long Functions of microtubules: – Shaping the cell – Guiding movement of organelles – Separating chromosomes during cell division

72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Centrosomes and Centrioles In many cells, microtubules grow out from a centrosome near the nucleus The centrosome is a “microtubule-organizing center” In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring

73. LE 6-22 0.25 µm Microtubule Centrosome Centrioles Longitudinal section of one centriole Microtubules Cross section of the other centriole

74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and Flagella Microtubules control the beating of cilia and flagella, locomotor appendages of some cells Cilia and flagella differ in their beating patterns Video: Chlamydomonas Video: Chlamydomonas Video: Paramecium Cilia Video: Paramecium Cilia

75. LE 6-23a 5 µm Direction of swimming Motion of flagella

76. LE 6-23b 15 µm Direction of organism’s movement Motion of cilia Direction of active stroke Direction of recovery stroke

77. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and flagella share a common ultrastructure: – A core of microtubules sheathed by the plasma membrane – A basal body that anchors the cilium or flagellum – A motor protein called dynein, which drives the bending movements of a cilium or flagellum Animation: Cilia and Flagella Animation: Cilia and Flagella

78. LE 6-24 0.5 µm Microtubules Plasma membrane Basal body Plasma membrane 0.1 µm Cross section of basal body Triplet Outer microtubule doublet 0.1 µm Dynein arms Central microtubule Cross-linking proteins inside outer doublets Radial spoke

79. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How dynein “walking” moves flagella and cilia: – Dynein arms alternately grab, move, and release the outer microtubules – Protein cross-links limit sliding – Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum

80. LE 6-25a Dynein “walking” Microtubule doublets ATP Dynein arm

81. LE 6-25b Wavelike motion Cross-linking proteins inside outer doublets ATP Anchorage in cell Effect of cross-linking proteins

82. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microfilaments (Actin Filaments) Microfilaments are solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits The structural role of microfilaments is to bear tension, resisting pulling forces within the cell They form a 3D network just inside the plasma membrane to help support the cell’s shape Bundles of microfilaments make up the core of microvilli of intestinal cells

83. LE 6-26 Microfilaments (actin filaments) Microvillus Plasma membrane Intermediate filaments 0.25 µm

84. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microfilaments that function in cellular motility contain the protein myosin in addition to actin In muscle cells, thousands of actin filaments are arranged parallel to one another Thicker filaments composed of myosin interdigitate with the thinner actin fibers Video: Cytoplasmic Streaming Video: Cytoplasmic Streaming

85. LE 6-27a Muscle cell Actin filament Myosin filament Myosin arm Myosin motors in muscle cell contraction

86. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Localized contraction brought about by actin and myosin also drives amoeboid movement Pseudopodia (cellular extensions) extend and contract through the reversible assembly and contraction of actin subunits into microfilaments

87. LE 6-27b Cortex (outer cytoplasm): gel with actin network Amoeboid movement Inner cytoplasm: sol with actin subunits Extending pseudopodium

88. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cytoplasmic streaming is a circular flow of cytoplasm within cells This streaming speeds distribution of materials within the cell In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming

89. LE 6-27c Nonmoving cytoplasm (gel) Cytoplasmic streaming in plant cells Chloroplast Streaming cytoplasm (sol) Cell wall Parallel actin filaments Vacuole

90. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intermediate Filaments Intermediate filaments range in diameter from 8– 12 nanometers, larger than microfilaments but smaller than microtubules They support cell shape and fix organelles in place Intermediate filaments are more permanent cytoskeleton fixtures than the other two classes

91. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 6.7: Extracellular components and connections between cells help coordinate cellular activities Most cells synthesize and secrete materials that are external to the plasma membrane These extracellular structures include: – Cell walls of plants – The extracellular matrix (ECM) of animal cells – Intercellular junctions

92. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Walls of Plants The cell wall is an extracellular structure that distinguishes plant cells from animal cells The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

93. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Walls of Plants Plant cell walls may have multiple layers: – Primary cell wall: relatively thin and flexible – Middle lamella: thin layer between primary walls of adjacent cells – Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall Plasmodesmata are channels between adjacent plant cells

94. LE 6-28 Central vacuole of cell Plasma membrane Secondary cell wall Primary cell wall Middle lamella 1 µm Central vacuole of cell Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata

95. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Extracellular Matrix (ECM) of Animal Cells Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) The ECM is made up of glycoproteins and other macromolecules Functions of the ECM: – Support – Adhesion – Movement – Regulation

96. LE 6-29a EXTRACELLULAR FLUID Proteoglycan complex Collagen fiber Fibronectin Integrin Micro- filaments CYTOPLASM Plasma membrane

97. LE 6-29b Polysaccharide molecule Carbo- hydrates Core protein Proteoglycan molecule Proteoglycan complex

98. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intercellular Junctions Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact Intercellular junctions facilitate this contact

99. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plants: Plasmodesmata Plasmodesmata are channels that perforate plant cell walls Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell

100. LE 6-30 Interior of cell Interior of cell 0.5 µm PlasmodesmataPlasma membranes Cell walls

101. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animals: Tight Junctions, Desmosomes, and Gap Junctions At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes (anchoring junctions) fasten cells together into strong sheets Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells Animation: Tight Junctions Animation: Tight Junctions Animation: Desmosomes Animation: Desmosomes Animation: Gap Junctions Animation: Gap Junctions

102. LE 6-31 Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm 0.1 µm Gap junction Extracellular matrix Space between cells Plasma membranes of adjacent cells Intermediate filaments Tight junction Desmosome Gap junctions

103. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cell: A Living Unit Greater Than the Sum of Its Parts Cells rely on the integration of structures and organelles in order to function For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane

104. LE 6-32 5 µm

105. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings HOMEWORK VOCABULARY 4 SQUARES

106. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START FUNCTION ASSOCIATED ORGANELLES AND STRUCTURES 1.CELL DIVISION 2. INFO STORAGE AND TRANSFERAL 3. ENERGY CONVERSION 4.MANUFACTURE OF MEMBRANES AND PRODUCTS 5. LIPID SYNTHESIS, DRUG DETOX 6. DIGESTION, RECYCLING 7. CONVERSION OF H202 TO WATER 8. STRUCTURAL INTEGRITY 9. MOVEMENT 10. EXCHANGE WITH ENVIRONMENT 11. CELL TO CELL CONNECTION

107. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CLASS START PAGE 123 SELF QUIZ