Class Notes 4:Cellular Transport and the Plasma Membrane

I. Structure of the Plasma Membrane

A. All cells have a plasma membrane. It is a PHOSPHOLIPID BILAYER

B. A phospholipid is a molecule with 3 parts:

1. Polar phosphate2. Glycerol3. Non- polar fatty acid tail

II. Other molecules of the cell membrane

A. Cholesterol -strengthens the membrane.

B. Transport proteins-like tunnels allowing certain substances in and out.

C. Carbohydrates- allow cells to identify eachother.

III. Methods of cellular transport:

A. The membrane has SELECTIVE PERMEABILITY- some but not all materials can cross.

B. Materials can move in and out of the cell in the following ways:

1. Passive Transport = no energy requireda. Diffusion

b. Facilitated diffusion2. Active Transport= energy required3. Endocytosis4. Exocytosis

IV. Passive transport

A. Very small molecules like 02 can pass right through the plasma membrane by diffusion.

B. Facilitated diffusion allows larger particles to go through transport proteins.

V. Active Transport

A. Movement of materials through a membrane against a concentration gradient is called Active Transport and requires energy.

B. Endocytosis

Some cells can take in large molecules, groups of molecules, or even whole cells = ENDOCYTOSIS

C. Exocytosis

1. Exocytosis is the explosion or secretion of materials from the cell (wastes, hormones)

2. Endocytosis and Exocytosis require energy!

Summary

Describe the structure of the plasma membrane. How do molecules get in and out? What is the difference between active and passive transport?