Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Cells Chapter 4 Copyright © McGraw-Hill Companies Permission required

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies

Cells

Chapter 4

Copyright © McGraw-Hill Companies Permission required for reproduction or display


Outline

• Cell Theory• Plasma Membrane• Prokaryotic Cells• Eukaryotic Cells• Cytoskeleton• Cell Organelles• Cell Movement• Diffusion and Osmosis• Bulk Passage


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.


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.


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.


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.



Lipid Bilayer


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.



Lipid Bilyer


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.


Prokaryotic Cells


Eukaryotic Cells

• Contain many membrane-bound interior compartments and a variety of organelles. Specialized structures performing specific

processes.- Nucleus


Cytoskeleton

• Cytoskeleton - dense network of protein fibers supporting cell shape. Microfilaments Microtubules Intermediate Fibers


Cell Organelles

• Eukaryotic cells thought to have evolved from endosymbiosis between different species of prokaryotes. Engulfed prokaryotes provided hosts with

certain metabolic advantages.


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.


Nucleus


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).


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.


Endomembrane System



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.


Mitochondria


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).


Chloroplasts


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.


Flagella and Cilia


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


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).




• Osmosis Diffusion of water across a membrane

toward the side with polar molecules that cannot traverse the membrane.




• 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.


Bulk Passage

• Endocytosis - Cell membrane engulfs particle and forms a vesicle, bringing the particle into the interior of the cell.

• Excoytosis - Reverse of endocytosis.



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.


Facilitated Diffusion



Active Transport

• Active Transport - Using energy to move molecules through membrane protein channels against a concentration gradient. Sodium-Potassium Pump Proton Pump


Active Transport



How Cells Get Information• Chemical information sensed by surface

receptor proteins. Hormone signals

• Voltage sensed by specialized ion channels.



Review

• Cell Theory• Plasma Membrane• Prokaryotic Cells• Eukaryotic Cells• Cytoskeleton• Cell Organelles• Cell Movement• Diffusion and Osmosis• Bulk Passage



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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Cells Chapter 4 Copyright © McGraw-Hill Companies Permission required