Membrane Fluidity : Its contribution to the Dynamic Nature of the Membrane

TeamMawadda Al-Naeeli

Pat Cipriano, Kim Conner, Lopa Das,Thea Edwards, Tara Luke

Facilitators: Michelle Withers & Karen York

Goal

• Understand how the chemical structure of cell membranes underlie their function and adaptability.

• u

OutcomesUpon completion of this teachable unit the student will:

• Explain how fluidity is changed by changes in the components of the membrane.

• Predict how the lipid composition changes to maintain fluidity in extreme environments.

• Practice drawing, reading and interpreting graphs.

Context

Introductory Biology

Omega 3 Fatty Acids

Have you ever heard of Omega 3 fatty acids?

What are they?

What are some good sources of Omega 3 fatty acids?

C-CC-H

Membrane proteins

Mouse cellHuman cell

http://www.youtube.com/watch?v=LicQb_SnCSI

Mixed proteinsafter 1 hour

Hybrid cell

Fluid nature of lipid bilayer of cell membrane

Fluid

Unsaturated hydrocarbontails

Viscous

Saturated hydrocarbon tails

A B

Decrease in fluidity with increase in cholesterol content

Clicker Question

How does an increase in temperature affect membrane fluidity?

A. Increases fluidityB. Decreases fluidityC. No change

Clicker Question

How does an increase in temperature affect membrane fluidity?

A. Increases fluidityB. Decreases fluidityC. No change

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

Warm Water Fishes

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

↓ ↑ ↓

Warm Water Fishes

↑ ↓ ↑

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

↓ ↓

Warm Water Fishes

↑ ↑

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

↓ ↑ ↓

Warm Water Fishes

↑ ↓ ↑

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

↓ ↑

Warm Water Fishes

↑ ↓

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

Cholesterol Unsaturated Fatty Acids

Saturated Fatty Acids

Cold Water Fishes

↓ ↑ ↓

Warm Water Fishes

↑ ↓ ↑

Consider cold water and warm water fishes.

How would membrane composition differ to maintain similar fluidity?

↑ ↓ --

• Using your dataset, draw a graph that would show the effects of changing temperature on membrane cholesterol and omega-3 fatty acid (unsaturated) content.

Hassett R P , and Crockett E L J Exp Biol 2009;212:71-77

Relationship between cholesterol content and habitat temperature in copepods.

Which of the following would occur when a tropical fish suddenly finds itself in the Arctic?

1. Membranes are more rigid2. Membranes are more fluid3. Membranes maintain the same fluidity

Which of the following would occur when a tropical fish suddenly finds itself in the Arctic?

1. Membranes are more rigid2. Membranes are more fluid3. Membranes maintain the same fluidity4. The organism dies5. The organism survives6. Membrane maintains function7. Membrane loses function8. Lipid composition changes9. Lipid composition stays the same

Which of the following would occur when considering the membrane of an organism that…

(is exposed to colder temperatures than it normally experiences?)(is exposed to warmer temperatures than it normally experiences?)(is a psychrophile?)(is a thermophile?)(has a high level of cholesterol in its membrane?)(has a low level of cholesterol in its membrane?)(contains mostly saturated fats?)(contains mostly unsaturated fats?)