Chapter 3 Notes

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Elaine N. Marieb Katja Hoehn
CHAPTER

PowerPoint® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College

Human Anatomy & Physiology
SEVENTH EDITION

Cells: The Living Units

3

P ART A

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But First… Let’s clean up…

Hydrophobic Hydrophilic

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Plasma Membrane Separates intracellular fluids from extracellular fluids

Plays a dynamic role in cellular activity
Just like the doors, windows, and walls of a house

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Fluid Mosaic Model Double bilayer of lipids (fats) with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids Glycolipids are lipids with bound carbohydrate Phospholipids have hydrophobic and hydrophilic bipoles Cholesterol provides fluidity of membrane

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Fluid Mosaic Model

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Figure 3.3

Membrane Junctions Tight junction – impermeable junction that encircles the cell Like a sewing stitch

Desmosome – anchoring junction scattered along the sides of cells Like an anchor

Gap junction – a nexus that allows chemical substances to pass between cells Like door in submarines or space stations

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Membrane Junctions: Tight Junction

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Figure 3.5a

Membrane Junctions: Desmosome

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Figure 3.5b

Membrane Junctions: Gap Junction

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Figure 3.5c

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Passive Membrane Transport: Diffusion Simple diffusion – non-polar and lipid-soluble substances Diffuse directly through the lipid bilayer Diffuse through channel proteins

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Passive Membrane Transport: Diffusion Facilitated diffusion
Transport of glucose, amino acids, and ions Transported substances bind to carrier proteins or pass through protein channels

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Carrier Proteins Are integral transmembrane proteins Show specificity for certain polar molecules including sugars and amino acids

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Diffusion Through the Plasma Membrane
Extracellular fluid Lipidsoluble solutes Lipid-insoluble solutes Small lipidinsoluble solutes Water molecules

Lipid bilayer

Cytoplasm (a) Simple diffusion directly through the phospholipid bilayer (b) Carrier-mediated facilitated diffusion via protein carrier specific for one chemical; binding of substrate causes shape change in transport protein (c) Channel-mediated facilitated diffusion through a channel protein; mostly ions selected on basis of size and charge (d) Osmosis, diffusion through a specific channel protein (aquaporin) or through the lipid bilayer

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Figure 3.7

Passive Membrane Transport: Osmosis

Occurs when the concentration of a solvent is different on opposite sides of a membrane

Diffusion of water across a semi-permeable membrane

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Effect of Membrane Permeability on Diffusion and Osmosis

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Figure 3.8a

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Effect of Membrane Permeability on Diffusion and Osmosis

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Figure 3.8b

Passive Membrane...
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