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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 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