Cells
Chapter 4
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Outline
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Cell Theory
Plasma Membrane
Prokaryotic Cells
Eukaryotic Cells
Cytoskeleton
Cell Organelles
Cell Movement
Diffusion and Osmosis
Bulk Passage
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Cell Theory
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Robert Hooke (1665)
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Observed thin slice of nonliving plant tissue.
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Observed honeycombed compartments he called cellulae (small rooms).
Matthias Schleiden (1838) first statement of cell theory.
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Cell Theory
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All organelles are composed of one or more cells, within which life processes occur.
Cells are smallest living things.
Life evolved only once, 3.5 billion years ago.
Cells arise only by division of a previously existing cell.
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Cell Size
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Cells range in size from 5-20 micrometers to
5 cm long.
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Most cells are small because larger cells do not function as efficiently.
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As cell size increases, volume increases more rapidly than surface area.
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Larger cells have less surface area per unit volume, thus less opportunity to interact with the environment.
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Cytoplasm fills cell interior.
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Plasma Membrane
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Cell membrane made up of diverse collection of proteins floating within lipid framework.
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Fluid Mosaic Model
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Lipid bilayer forms when phospholipids are placed in water.
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Hydrophobic tails pointing in, hydrophilic heads pointing outward.
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Lipid Bilayer
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Plasma Membrane
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Membrane Proteins - Float freely within lipid bilayer.
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Cell Surface Proteins - Act as markers to identify particular types of cells.
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Transmembrane Proteins - Span entire membrane. Provide channels for molecule passage.
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Lipid Bilyer
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Prokaryotic Cells
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Prokaryotes have a relatively uniform cytoplasm not subdivided by interior membranes (No interior compartments).
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Bacteria are simplest cellular organisms.
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Over 2,500 recognized species.
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Almost all are contained by a cell wall.
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Some bacteria contain another layer
( capsule ) enclosing the cell.
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Prokaryotic Cells
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Eukaryotic Cells
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Contain many membrane-bound interior compartments and a variety of organelles.
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Specialized structures performing specific processes.
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Nucleus
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Cytoskeleton
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Cytoskeleton - dense network of protein fibers supporting cell shape.
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Microfilaments
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Microtubules
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Intermediate Fibers
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Cell Organelles
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Eukaryotic cells thought to have evolved from endosymbiosis between different species of prokaryotes.
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Engulfed prokaryotes provided hosts with certain metabolic advantages.
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Nucleus
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Nucleus - Command and control center.
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Bound by nuclear envelope.
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Covered with nuclear pores embedded by proteins permitting proteins and RNA to pass in and out of nucleus.
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Contain chromosomes holding DNA.
Nucleolus - Cluster of genes encoding rRNA.
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Ribosome reads RNA and directs protein building.
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Nucleus
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Endomembrane System
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Endoplasmic Reticulum
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Internal membrane creating channels and membrane-enclosed vesicles.
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Carbohydrates and lipids manufactured on the surface.
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Proteins for export produced on surface covered with ribosomes (Rough ER).
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Endomembrane System
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Golgi Complex
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Golgi bodies are scattered throughout the cytoplasm. Function in collection, packaging, and distribution of molecules manufactured in the cell.
Lysosomes
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Arise from Golgi complex and break down macromolecules. (Recycling center)
Peroxisomes - Vesicles carrying out specific chemical functions.
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Endomembrane System
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DNA Containing Organelles
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Mitochondria
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Double membrane organelles that extract energy from organic molecules.
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( Oxidative Metabolism )
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Inner membrane bent into numerous folds
( cristae ) that partitions mitochondrion into inner matrix and outer compartment.
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Mitochondria
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DNA Containing Organelles
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Chloroplasts
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Double membrane organelles that serve as site of photosynthesis.
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Inner membranes fused to form stacks of thylakoids , which are stacked on top of one another to form a column ( granum ).
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Interior bathed with semiliquid ( stroma ).
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Chloroplasts
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Cell Movement
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Microvilli project outward form surface of animal cells.
Arrangement of actin filaments within cell cytoplasm allow cells to crawl.
Flagella are fine, threadlike organelles protruding from cell surface.
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Arise from basal body and consist of nine microtubule pairs surrounding two central pairs.
Cilia - Short, numerous flagella.
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Flagella and Cilia
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Plant Cells Are Unique
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Central Vacuole - Large storage center for certain cell substances, and increases surface to volume ratio.
Cell Walls - Composed of cellulose fibers.
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Primary Walls
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Middle Lamella
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Secondary Walls
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Diffusion and Osmosis
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Diffusion
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Random motion of molecules produces uniform mixture due to net movement of molecules down a concentration gradient
(high concentration to low concentration).
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Diffusion and Osmosis
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Osmosis
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Diffusion of water across a membrane toward the side with polar molecules that cannot traverse the membrane.
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Diffusion and Osmosis
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Solute - Substance dissolved in a solution.
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Hyperosmotic - Solution with higher concentration of solutes.
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Hypoosmotic - Solution with lower concentration of solutes.
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Isomotic - Osmotic concentration of both solution are equal.
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Osmotic Pressure - Pressure caused by movement of water into a cell.
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Bulk Passage
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Endocytosis - Cell membrane engulfs particle and forms a vesicle, bringing the particle into the interior of the cell.
Excoytosis - Reverse of endocytosis.
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Selective Permeability
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Protein channels in membrane only allow passage of certain kinds of molecules.
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Selective Diffusion allows molecules to move through channels and equalize concentrations.
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Facilitated Diffusion - net movement down a concentration gradient facilitated by carrier proteins.
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Facilitated Diffusion
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Active Transport
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Active Transport - Using energy to move molecules through membrane protein channels against a concentration gradient.
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Sodium-Potassium Pump
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Proton Pump
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Active Transport
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How Cells Get Information
Chemical information sensed by surface receptor proteins.
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Hormone signals
Voltage sensed by specialized ion channels.
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Review
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Cell Theory
Plasma Membrane
Prokaryotic Cells
Eukaryotic Cells
Cytoskeleton
Cell Organelles
Cell Movement
Diffusion and Osmosis
Bulk Passage
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies