The document explains the structure and function of cell membranes, primarily detailing the fluid-mosaic model that describes their pliable nature and composition of various molecules. It outlines the selectively permeable nature of the membrane, highlighting factors like size and polarity that affect substance passage. Additionally, it discusses the roles of phospholipids, cholesterol, and different types of proteins in membrane functionality and identification.

1. Cell Membrane
Structure and Function

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Membrane Design
2
 fluid-mosaic model
a. Fluid = pliable/easily moved
b. Mosaic = made of many different
molecules (lipids, proteins, carbohydrates)
Cell Membrane Animation

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3
Predict the two reasons things can’t directly go through
the membrane:
Selectively Permeable
1) Size (duh)
2) Polarity (from last unit)

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4
The cell membrane only lets certain substances in and
out of the cell
Selectively Permeable

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Phosopholipid Bi-Layer
5
-polar heads are hydrophilic “water loving”
-tails (fatty acids) are hydrophobic “water fearing” and face inward

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cholesterol
 Type of steroid (lipid)
 Changes fluidity of cell membrane
 Higher temps – stiffens membrane
 Lower temps – prevents membrane from freezing

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Proteins
7
 Recognition Proteins
 Proteins that have carbohydrate
chains attached
 Carbohydrate chains aid in cell
identification
 “Name Tags”
 Example: Red Blood Cells (A, B),
Identify Viruses as foreign
 Receptor Proteins
 Proteins that receive chemical
signals from other cells
 Such as nervous system cells

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Channel Proteins
 Proteins that involved in letting certain substances in and out
of cells
 Aquaporins- let water in and out of cells
Proteins

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
9
 Integral
 Proteins that cross both layers of the phosphoplipid
bilayer
 Peripheral
 proteins that are only on the top half or bottom half
of the phospholipid bilayer
Proteins