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1
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 cells• The cell is the fundamental unit of
life• All cells arise from previous cells
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Observing Cells: The Microscope
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Cell theory
• (1839)Theodor Schwann & Matthias Schleiden
“ all living things are made of cells”• (50 yrs. later) Rudolf Virchow
“all cells come from cells”
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Principles of Cell Theory
• All living things are made of cells• Smallest living unit of structure
and function of all organisms is the cell
• All cells arise from preexisting cells
(this principle discarded the idea of spontaneous generation)
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Cell Size
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iClicker Question
• What is a cell?–A) The largest living units within our
bodies.–B) Enzymes that "eat" bacteria–C) Microscopic fundamental units of all
living things.–D) All of the above.
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iClicker Question
• All cells are too small to be seen with the unaided eye and must be studied with a microscope.
– A True– B False
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Cells Have Large Surface Area-to-Volume Ratio
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Characteristics of All Cells• A surrounding membrane• Protoplasm – cell contents in thick fluid• Organelles – structures for cell function• Control center with DNA
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iClicker Question
• What does an electron microscope use to illuminate objects?
– A light– B protons– C proteins– D electrons
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Molecule Movement & Cells
• Passive Transport
• Active Transport
• Endocytosis (phagocytosis & pinocytosis)
• Exocytosis
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Water: Medium for Metabolism
• Liquid medium for metabolism and its importance
• Role of water (H2O)– Physical properties (e.g., polarity, phases)– Chemical properties (e.g., pH, solution)
• Exquisite and unique properties of H2O
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Passive Transport
• No energy required
• Move due to gradient–differences in concentration, pressure,
charge
• Move to equalize gradient–High moves toward low
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Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion
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iClicker Question
• An essential and distinctive feature of all cells is a membrane that isolates and protects the interior from the outer environment.
– A True– B False
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Diffusion
• Molecules move to equalize concentration
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Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water– Into cell–Out of cell
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Solution Differences & Cells• solvent + solute = solution• Hypotonic
–Solutes in cell more than outside–Outside solvent will flow into cell
• Isotonic–Solutes equal inside & out of cell
• Hypertonic–Solutes greater outside cell– Fluid will flow out of cell
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Facilitated Diffusion
• Differentially permeable membrane• Channels (are specific) help
molecule or ions enter or leave the cell
• Channels usually are transport proteins (aquaporins facilitate the movement of water)
• No energy is used
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Process of Facilitated Transport
• Protein binds with molecule• Shape of protein changes• Molecule moves across membrane
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Active Transport
• Molecular movement• Requires energy (against gradient)• Example is sodium-potassium pump
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Endocytosis
• Movement of large material–Particles–Organisms –Large molecules
• Movement is into cells• Types of endocytosis
– bulk-phase (nonspecific)– receptor-mediated (specific)
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Process of Endocytosis• Plasma membrane surrounds
material• Edges of membrane meet• Membranes fuse to form vesicle
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Forms of Endocytosis• Phagocytosis – cell eating• Pinocytosis – cell drinking
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Exocytosis• Reverse of endocytosis• Cell discharges material
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Exocytosis• Vesicle moves to cell surface• Membrane of vesicle fuses • Materials expelled
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iClicker Question
In which decade were you born?• A 1990s• B 1980s• C 1970s• D 1960s• E 1950s
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iClicker Question
In which year was Geller’s first peer-reviewed paper published?
• A 1964• B 1974• C 1984• D 1994• E 2004
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iClicker Question
• In which journal was Geller’s first pee-reviewed paper published?
• A Astrophysical Journal• B Astronomical Journal• C Journal of Chromatography• D Journal of Physics• E The Physics Teacher
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How Does a Cell Work?
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Cell Membranes
• Cell Membranes– Isolate cell– Separates cell parts
• Transport– Individual molecules– Specific materials
• channels
• Receptors– Bind molecules
• Cell Wall– Plants
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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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The Energy Organelles: Chloroplasts and Mitochondria
• Organelle– Specialized structure in cell
• Chloroplasts– Energy transformation
• chlorophyll– Plant cells only– Double membrane
• 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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iClicker Question
• Cells that do not contain a nucleus are called:
– A eukaryotes– B prokaryotes– C likaryotes
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iClicker Question
• Any specialized structure in the cell is called:
– A an endoplasmic reticulum– B a chromatin– C an organelle
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iClicker Question
• What is the basic molecular structure of cell membranes?
– A lipid bilayer– B carbohydrate bilayer– C protein bilayer
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iClicker Question
• The fluid that takes up the spaces between all the complexity of the specialized structures in cells is called:
– A deionized water– B protoplasm– C cytoplasm– D molasses
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iClicker Question
• The cell structure which divides the inside of the cell from the outside is the:
– A cell membrane– B cell coat– C nuclear membrane
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iClicker Question
• What structure connects plant cells to each other and often account for about a third of a living plant’s mass?
– A middle lamella– B cell wall– C cell membrane
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iClicker Question
• In most cells the most prominent and important interior structure is the:
– A nucleus– B chromosome– C endoplasmic reticulum
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iClicker Question
• Which organelle is the place where molecules react with oxygen to produce the cell’s energy?
– A endoplasmic reticulum– B mitochondria– C chloroplasts
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iClicker Question
• More advanced single-celled organism that do contain a nuclei are called:
– A eukaryotes– B prokaryotes– C likaryotes
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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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Photosynthesis• Photosynthesis
–Convert sunlight to energy
• Process–Energy + CO2 + H2O carbohydrate + O2
• Colors
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Glycolysis: The First Step in Energy Generation in the Cell
• Respiration– Oxidation of carbohydrate– Retrieves energy in glucose– Aerobic
• Process– Glycolysis
• Split glucose• Result
– Pyruvic acid– 2 ATP– 2 energy carriers
• Convert energy carriers to 2-3 ATP– 1 molecule glucose = 6-8 ATP
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Fermentation: A Way to Keep Glycolysis Going
• Fermentation–Anaerobic– Inefficient
• Yeast–alcohol
• Animal cells–Lactic acid
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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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iClicker Question
• The cell’s process of deriving energy form its surroundings is called:
– A photosynthesis– B metabolism– C respiration
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iClicker Question
• What mechanism do plants use to convert the energy of sunlight into energy stored in carbohydrates?
– A photosynthesis– B metabolism– C glycolysis
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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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Meiosis
• Meiosis– Sexual reproduction– 1 cell forms 4 gametes
• Gametes are genetically unique
• Process– Copy chromosomes– Crossing over– Segregation– Segregation again
• Result– 4 daughter cells– ½ normal chromosomes
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Meiosis
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iClicker Question
• By what process do most cells divide?
– A mitosis– B meiosis– C glycolysis
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