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