Chapter 7. A Tour of the Cell

Transcription

1 Chapter 7 A Tour of the Cell

2 How Big is a...?

3 microscopes Glass lenses were invented in Middle East Came to Europe after crusades s compound two lenses 1,000 x upper limit

4 1665 Robert Hooke found dead cells in cork Molecular Expressions Microscopy Primer: Museum of Microscopy - Hooke's Microscope

5 1673 Anton van Leeuwenhoek observed microscopic living organisms animicules

6 1824 Henri Dutrochet all living things are made of cells 1831 Robert Brown (the Brownian motion guy) observed the nucleus

7 Schleiden- all plants are made of cells Schwann - animals are made of cells Schleiden Schwann

8 1850- Louis Pasteur pasteurization (of wine)

9 1855- Dr. Virchow- physician- cells come from preexisting cells

10 1860s Civil War soldiers died from infections

11 The Cell Theory All living things are composed of one or more cells 2. The cell is the basic unit of structure and function 1. 3.All cells come from preexisting cells

12 1950 s Electron microscope (EM)- thousands of times more powerful but not alive (TEM)

13 1970 s Scanning em.-(sem) 3d images

14 1980 s - scanning tunneling EM- you can see individual atoms and push them around

15 So the Japanese pushed CO

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17 Cell Fractionation Is used to separate the various parts of cells for further study. An example of reductionism.

18 You blend the cells to break them open and spin them down to separate heavier parts.

19 TWO CELL TYPES

20 1) Prokaryote cells 1) Prokaryote cells (no nucleus) before nucleus Domains Eubacteria and Archaea - Bacteria Kingdom Monera - single celled

21 2) Eukaryotic cells (has nucleus) Domain Eukarya - membrane bound organelles Kingdom Protists Protista fungus Fungi plants Plantae animals Animalia

22 Limits to cell size Lower limit to cell size: The cell must be big enough to contain DNA, RNA and several ribosomes. 20 to 100 nanometer

23 Upper Limits to Cell Size: The cell must be small because: 1) Diffusion- materials (H20 and CO2) can only diffuse so far so fast 2) DNA- controls cell functions bigger cells either split or have many nuclei. Most importantly 3) Surface area to volume ratio

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25 Ratio Surface Area vs. Volume Ratio Cube Sphere Long cylinder Squat cylinder Size of Object

26 Ratio SA:V X:1 Surface Area to Volume Ratio Series1 Cube sphere tall cylinder squat cylinder Size of Cell 1 7

27 Parts of the Eukaryotic Cell Cells are compartmentalized by membranes to allow the many different reactions to occur simultaneously. Many reactions occur in the membrane lining. Organelles - are specialized internal structures.

28 Types Prokaryote of cells bacteria cells - no organelles - organelles Eukaryote animal cells Eukaryote plant cells

29 Why organelles? Specialized structures specialized functions cilia or flagella for locomotion Containers partition cell into compartments create different local environments separate ph, or concentration of materials distinct & incompatible functions lysosome & its digestive enzymes Membranes as sites for chemical reactions unique combinations of lipids & proteins embedded enzymes & reaction centers chloroplasts & mitochondria mitochondria chloroplast Golgi ER

30 Cells gotta work to live! What jobs do cells have to do? make proteins proteins control every cell function make energy for daily life for growth make more cells growth repair renewal

31 Proteins do all the work! proteins DNA organism cells Repeat after me Proteins do all the work

32 Cells functions Building proteins read DNA instructions build proteins process proteins folding modifying removing amino acids adding other molecules» e.g, making glycoproteins for cell membrane address & transport proteins

33 Building Proteins Organelles involved nucleus ribosomes endoplasmic reticulum (ER) Golgi apparatus vesicles nucleus ribosome ER The Protein Assembly Line Golgi apparatus vesicles

34 Nucleus DNA Function protects DNA Structure nuclear envelope double membrane membrane fused in spots to create pores allows large macromolecules to pass through What kind of molecules need to pass through? nuclear pores nucleolus histone protein chromosome nuclear pore nuclear envelope

35 1 nuclear membrane DNA production of mrna from DNA in nucleus Nucleus mrna mrna travels from nucleus to ribosome in cytoplasm through nuclear pore 2 nuclear pore mrna small ribosomal subunit large ribosomal subunit cytoplasm

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37 Function Nucleolus ribosome production build ribosome subunits from rrna & proteins exit through nuclear pores to cytoplasm & combine to form functional ribosomes large subunit small subunit rrna & proteins ribosome nucleolus

38 Ribosomes large subunit Function protein production Structure rrna & protein small subunit 2 subunits combine 0.08mm Ribosomes Rough ER Smooth ER

39 Free ribosomes Types of Ribosomes suspended in cytosol synthesize proteins that function in cytosol Bound ribosomes attached to endoplasmic reticulum synthesize proteins for export or for membranes membrane proteins

40 Function Endoplasmic Reticulum processes proteins manufactures membranes synthesis & hydrolysis of many compounds Structure membrane connected to nuclear envelope & extends throughout cell

41 Types of ER rough smooth

42 Rough ER function Produce proteins for export out of cell protein secreting cells packaged into transport vesicles for export Which cells have lot of rough ER?

43 Smooth ER function Membrane production Many metabolic processes synthesis synthesize lipids hydrolysis oils, phospholipids, steroids & sex hormones hydrolyze glycogen into glucose in liver detoxify drugs & poisons in liver ex. alcohol & barbiturates

44 Membrane Factory Build new membrane synthesize phospholipids builds membranes ER membrane expands bud off & transfer to other parts of cell that need membranes

45 Synthesizing proteins cisternal space polypeptide signal sequence ribosome ribosome mrna membrane of endoplasmic reticulum cytoplasm

46 Golgi Apparatus Function Which cells have lots of Golgi? finishes, sorts, tags & ships cell products like UPS shipping department ships products in vesicles membrane sacs UPS trucks secretory vesicles transport vesicles

47 Golgi Apparatus

48 Vesicle transport protein vesicle budding from rough ER migrating transport vesicle fusion of vesicle with Golgi apparatus ribosome

49 nucleus DNA endoplasmic reticulum protein on its way! TO: RNA vesicle TO: ribosomes TO: vesicle protein TO: finished protein Making Proteins Golgi apparatus

50 Putting it together nucleus nuclear pore cell membrane Making proteins protein secreted rough ER ribosome vesicle proteins smooth ER cytoplasm transport vesicle Golgi apparatus

51 Lysosomes lysosomes Function digest food clean up & recycle digest broken organelles Structure membrane sac of digestive enzymes small food particle digesting broken organelles vacuole digesting food

52 When things go bad Diseases of lysosomes are often fatal digestive enzyme not working in lysosome picks up biomolecules, but can t digest one lysosomes fill up with undigested material grow larger & larger until disrupts cell & organ function lysosomal storage diseases more than 40 known diseases example: Tay-Sachs disease build up undigested fat in brain cells

53 Phagocytosis macrophages white blood cells Autophagy recycling your own stuff Lysosomes absorb and digest stuff in cells. Liver cells recycle ½ of all macromolecules everyday.

54 But sometimes cells need to Lysosomes can be die used to kill cells when they are supposed to be destroyed some cells have to die for proper development in an organism apoptosis auto-destruct process lysosomes break open & kill cell ex: tadpole tail gets re-absorbed when it turns into a frog ex: loss of webbing between your fingers during fetal development

55 Fetal development syndactyly 6 weeks 15 weeks

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58 Making Energy Cells must convert incoming energy to forms that they can use for work mitochondria: from glucose to ATP chloroplasts: from sunlight to ATP & carbohydrates ATP = active energy carbohydrates = stored energy ATP ATP +

59 Mitochondria & Chloroplasts Important to see the similarities transform energy generate ATP double membranes = 2 membranes semi-autonomous organelles move, change shape, divide internal ribosomes, DNA & enzymes

60 Function cellular respiration generate ATP Mitochondria from breakdown of sugars, fats & other fuels in the presence of oxygen break down larger molecules into smaller to generate energy = catabolism generate energy in presence of O 2 = aerobic respiration

61 Structure 2 membranes Mitochondria smooth outer membrane highly folded inner membrane cristae fluid-filled space between 2 membranes internal fluid-filled space mitochondrial matrix DNA, ribosomes & enzymes Why 2 membranes? increase surface area for membrane-bound enzymes that synthesize ATP

62 Mitochondria

63 Membrane-bound Enzymes glucose + oxygen carbon + water + energy dioxide C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP

64 Dividing Mitochondria Who else divides like that? What does this tell us about the evolution of eukaryotes?

65 Mitochondria Almost all eukaryotic cells have mitochondria there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria number of mitochondria is correlated with aerobic metabolic activity more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: muscle cells nerve cells

66 Mitochondria are everywhere!! animal cells plant cells

67 Chloroplasts Chloroplasts are plant organelles class of plant structures = plastids amyloplasts store starch in roots & tubers chromoplasts store pigments for fruits & flowers chloroplasts store chlorophyll & function in photosynthesis in leaves, other green structures of plants & in eukaryotic algae

68 Structure Chloroplasts 2 membranes stroma = internal fluid-filled space DNA, ribosomes & enzymes thylakoids = membranous sacs where ATP is made grana = stacks of thylakoids Why internal sac membranes? increase surface area for membrane-bound enzymes that synthesize ATP

69 Membrane-bound Enzymes carbon dioxide + water + energy glucose + oxygen 6CO 2 + 6H 2 O + light C 6 H 12 O 6 6O energy + 2

70 Chloroplasts Function photosynthesis generate ATP & synthesize sugars transform solar energy into chemical energy produce sugars from CO 2 & H 2 O Semi-autonomous moving, changing shape & dividing can reproduce by pinching in two Who else divides like that? bacteria!

71 Chloroplasts Why are chloroplasts green?

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73 Mitochondria & chloroplasts are different Organelles not part of endomembrane system Grow & reproduce semi-autonomous organelles Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes Own circular chromosome directs synthesis of proteins produced by own internal ribosomes ribosomes like bacterial ribosomes Who else has a circular chromosome not bound within a nucleus? bacteria

74 Food & water storage food vacuoles plant cells central vacuole animal cells contractile vacuole

75 Function Vacuoles & vesicles little transfer ships Food vacuoles phagocytosis, fuse with lysosomes Contractile vacuoles in freshwater protists, pump excess H 2 O out of cell Central vacuoles in many mature plant cells

76 Cytoskeleton Function structural support maintains shape of cell provides anchorage for organelles protein fibers» microfilaments, intermediate filaments, microtubules motility cell locomotion cilia, flagella, etc. regulation organizes structures & activities of cell

77 Cytoskeleton actin microtubule nuclei

78 Centrioles Cell division in animal cells, pair of centrioles organize microtubules spindle fibers guide chromosomes in mitosis

79 Cells need to make more cells! Making more cells to replace, repair & grow, the cell must copy their DNA make extra organelles divide the new DNA & new organelles between 2 new daughter cells organelles that do this work nucleus centrioles

80 Centrioles Function help coordinate cell division Structure one pair in each cell motor proteins

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84 Putting it all together animal cells plant cells

85 Chapter 8 Membrane Structure and Function

86 Cell Membrane A. Phospholipid bilayer AMPHIPATHIC molecule 1. polar head (hydrophillic) 2 nonpolar tails (hydrophobic)

87 Phospholipids will form layers and bilayers in water

88 Arranged as a Phospholipid bilayer Serves as a cellular barrier / border polar hydrophilic heads sugar H 2 O salt nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads waste lipids

89 Freeze fracturing revealed the structure

90 Types of movemen

91 Studies with mouse cells showed that the lipids can move, think ping pong balls on a pool.

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93 Transmembrane protein

94 Membranes have sidedness (inside versus outside)

95 Overview Cell membrane separates living cell from nonliving surroundings thin barrier = 8nm thick Controls traffic in & out of the cell selectively permeable allows some substances to cross more easily than others hydrophobic vs hydrophilic Made of phospholipids, proteins & other macromolecules

96 Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Glycoprotein Extracellular fluid Glycolipid Phospholipids Peripheral protein Cholesterol Cytoplasm Transmembrane proteins Filaments of cytoskeleton

97 Membrane fat composition varies Fat composition affects flexibility membrane must be fluid & flexible about as fluid as thick salad oil % unsaturated fatty acids in phospholipids keep membrane less viscous cold-adapted organisms, like winter wheat increase % in autumn cholesterol in membrane

98 Membrane Proteins Proteins determine membrane s specific functions cell membrane & organelle membranes each have unique collections of proteins Membrane proteins: peripheral proteins loosely bound to surface of membrane cell surface identity marker (antigens) integral proteins penetrate lipid bilayer, usually across whole membrane transmembrane protein transport proteins channels, permeases (pumps)

99 Why are proteins the perfect molecule to build structures in the cell membrane?

100 Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic

101 Classes of amino acids What do these amino acids have in common? I like the polar ones the best! polar & hydrophilic

102 Proteins domains anchor molecule Within membrane nonpolar amino acids hydrophobic anchors protein into membrane On outer surfaces of membrane polar amino acids hydrophilic extend into extracellular fluid & into cytosol Polar areas of protein Nonpolar areas of protein

103 Examples Retinal chromophore H + NH 2 water channel in bacteria Porin monomer b-pleated sheets Bacterial outer membrane Nonpolar (hydrophobic) COOH a-helices in the cell membrane H + Cytoplasm proton pump channel in photosynthetic bacteria function through conformational change = shape change

104 Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Enzyme activity Cell surface receptor Cell surface identity marker Cell adhesion Attachment to the cytoskeleton

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109 Membrane carbohydrates Play a key role in cell-cell recognition ability of a cell to distinguish one cell from another antigens important in organ & tissue development basis for rejection of foreign cells by immune system

110 Diffusion 2nd Law of Thermodynamics governs biological systems universe tends towards disorder (entropy) Diffusion movement from high low concentration

111 Diffusion Move from HIGH to LOW concentration passive transport no energy needed movement of water diffusion osmosis

112 Diffusion across cell membrane Cell membrane is the boundary between inside & outside separates cell from its environment IN food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O Can it be an impenetrable boundary? IN cell needs materials in & products or waste out OUT NO! OUT waste ammonia salts CO 2 H 2 O products

113 Diffusion through phospholipid bilayer What molecules can get through directly? fats & other lipids inside cell NH 3 lipid salt What molecules can NOT get through directly? polar molecules ions H 2 O outside cell sugar aa H 2 O salts, ammonia large molecules starches, proteins

114 Channels through cell membrane Membrane becomes semi-permeable with protein channels specific channels allow specific material across cell membrane inside cell H 2 O aa sugar NH 3 salt outside cell

115 Facilitated Diffusion Diffusion through protein channels channels move specific molecules across cell membrane no energy needed facilitated = with help open channel = fast transport high low The Bouncer

116 The Special Case of Water Movement of water across the cell membrane

117 Osmosis is diffusion of water Water is very important to life, so we talk about water separately Diffusion of water from high concentration of water to low concentration of water across a semi-permeable membrane

118 Concentration of water Direction of osmosis is determined by comparing total solute concentrations Hypertonic - more solute, less water Hypotonic - less solute, more water Isotonic - equal solute, equal water water hypotonic hypertonic net movement of water

119 Managing water balance Cell survival depends on balancing water uptake & loss freshwater balanced saltwater

120 Managing water balance Isotonic animal cell immersed in mild salt solution example: blood cells in blood plasma problem: none no net movement of water» flows across membrane equally, in both directions volume of cell is stable balanced

121 Managing water balance Hypotonic ATP a cell in fresh water example: Paramecium problem: gains water, swells & can burst water continually enters Paramecium cell solution: contractile vacuole pumps water out of cell ATP plant cells turgid freshwater

122 Water regulation Contractile vacuole in Paramecium ATP

123 Managing water balance Hypertonic a cell in salt water example: shellfish problem: lose water & die solution: take up water or pump out salt plant cells plasmolysis = wilt saltwater

124 Aquaporins Water moves rapidly into & out of cells evidence that there were water channels Peter Agre John Hopkins Roderick MacKinnon Rockefeller

125 Osmosis.05 M.03 M Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic Which way does the water flow? in or out of cell

126 Active Transport Cells may need to move molecules against concentration gradient shape change transports solute from one side of membrane to other protein pump costs energy = ATP low conformational change ATP high The Doorman

127 Active transport Many models & mechanisms ATP ATP antiport symport

128 Getting through cell membrane Passive Transport Simple diffusion diffusion of nonpolar, hydrophobic molecules lipids high low concentration gradient Facilitated transport diffusion of polar, hydrophilic molecules through a protein channel high low concentration gradient Active transport diffusion against concentration gradient low high uses a protein pump requires ATP ATP

129 Transport summary simple diffusion facilitated diffusion active transport ATP

130 How about large molecules? Moving large molecules into & out of cell through vesicles & vacuoles endocytosis phagocytosis = cellular eating pinocytosis = cellular drinking exocytosis exocytosis

131 Endocytosis phagocytosis fuse with lysosome for digestion pinocytosis non-specific process receptor-mediated endocytosis triggered by molecular signal

132 Sodium Potassium Pump

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134 Cotransport

135 Functions storage Vacuoles in plants stockpiling proteins or inorganic ions depositing metabolic byproducts storing pigments storing defensive compounds against herbivores selective membrane control what comes in or goes out

136 Peroxisomes Other digestive enzyme sacs in both animals & plants breakdown fatty acids to sugars easier to transport & use as energy source detoxify cell detoxifies alcohol & other poisons produce peroxide (H 2 O 2 ) must breakdown H 2 O 2 H 2 O