ch21
TRANSCRIPT
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The Living Cell
Chapter 21
Great Idea:Life is based on chemistry,
and chemistry takes place in cells
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Chapter Outline
• The Nature and Variety of Cells• How Does a Cell Work?• Metabolism: Energy and Life• Cell Division
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The Nature and Variety of Cells
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The Cell Theory
• All living things are composed of one or more cells
• The cell is the fundamental unit of life
• All cells arise from previous cells
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Science in the Making
• The discovery of cells– Robert Hooke– Anton van Leeuwenhoek
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Cork Cells
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Observing Cells: The Microscope
• Early microscopes• Light microscope• Electron microscope
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Light Microscope
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Electron Microscope
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Electron Microscope and Photograph
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How Does a Cell Work?
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The Cell Is Like a Refinery
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Cell Membranes
• Cell membranes– Isolate cell– Separates cell parts
• Transport– Individual molecules– Specific materials
•Channels
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Membrane Lipid Bilayer
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Cell Membranes – cont.
• Receptors– Bind molecules
• Cell Wall– Plants
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The Action of Cell Receptors
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Plant Cell
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Plant Cell
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The Nucleus
• Nucleus– Contains genetic material
• Prokaryotes– No nucleus
• Eukaryotes– Nucleus
• Double Membrane
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Nucleus Surrounded by a Double Membrane
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Terms Related to Cells and Single-Celled Organisms
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Plant Cell
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Animal Cell
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Energy Organelle - Chloroplasts
• Organelle– Specialized structure in cell
• Chloroplasts– Energy transformation
•Chlorophyll
– Plant cells only– Double membrane– Own DNA
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Energy Organelle –Mitochondria
• Mitochondria– Produces cells energy– Double membrane– Own DNA
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Cytoskeleton
• Cytoskeleton– Gives cell shape– Anchors– Allows movement– Transport system
•Within cell
• Structure– Strong filaments– Complex web
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Cytoskeleton
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Organelles and Their Functions
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Metabolism: Energy and Life
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The Cell’s Energy Currency
• Adenosine triphosphate (ATP)– Provides energy
• Structure– 3 phosphate groups– Sugar molecule: ribose– Adenine
• Function– Removal of phosphate group provides energy
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Structure of ATP
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Photosynthesis
• Photosynthesis– Convert sunlight to energy
• Process– Energy + CO2 + H2O carbohydrate + O2
• Colors
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Photosynthesis
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Glycolysis: The First Step in Energy Generation in the Cell
• Respiration– Oxidation of carbohydrate– Retrieves energy in glucose– Aerobic
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Glycolysis
• Process– Glycolysis
•Split glucose•Result
– 2 pyruvic acid– 2 ATP– 2 energy carriers
•Convert energy carriers to 2–3 ATP
– 1 molecule glucose = 6–8 ATP
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Glycolysis
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Fermentation: A Way to Keep Glycolysis Going
• Fermentation– Anaerobic– Inefficient
• Yeast– Alcohol
• Animal cells– Lactic acid
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Uses of Fermentation
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The Final Stages of Respiration
• Krebs cycle– Glucose broken down
– CO2 produced
– ATP – Energy-carrying molecules
• Result– 36–38 ATP
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Water Vapor Expelled during Respiration
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Cell Division
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Mitosis
• Mitosis– Cell division– Not for sexual reproduction
• Chromosomes• Process
– Copy chromosomes– Spindle fibers– Migration of chromosomes– Nuclear membrane reforms
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Mitosis
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Human Cell Dividing
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Meiosis
• Meiosis– Sexual reproduction– 1 cell forms 4 gametes
•Gametes are genetically unique•Contain half the number of chromosomes
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Process of Meiosis
• Process– Copy chromosomes– Crossing over– Segregation– Segregation again
• Result– 4 daughter cells– ½ normal number of chromosomes
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Meiosis
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Crossing Over
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Thinking More about Cells
• Biochemical evidence for evolution