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

Outcomes Upon 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-C C-H 6

Fluid nature of lipid bilayer of cell membrane Mixed proteins after 1 hour Membrane proteins Mouse cell Human cell Hybrid cell http://www.youtube.com/watch?v=LicQb_SnCSI 7

A B Viscous Fluid Saturated hydrocarbon tails Unsaturated hydrocarbon tails B 8

Decrease in fluidity with increase in cholesterol content

Clicker Question How does an increase in temperature affect membrane fluidity? A. Increases fluidity B. Decreases fluidity C. No change

Clicker Question How does an increase in temperature affect membrane fluidity? A. Increases fluidity B. Decreases fluidity C. No change

↑ ↓ -- 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? ↑ ↓ -- Cholesterol Unsaturated Fatty Acids Saturated Fatty Acids Cold Water Fishes ↓ ↑ Warm Water Fishes

Using your dataset, draw a graph that would show the effects of changing temperature on membrane cholesterol and omega-3 fatty acid (unsaturated) content. Identify the dependent and independent variables? What is the likely temperature range?

Relationship between cholesterol content and habitat temperature in copepods. Ask students to compare their graphs with a real data set. Anticipate that omega-3 graph would go the other way (negative correlation) Hassett R P , and Crockett E L J Exp Biol 2009;212:71-77

Which of the following would occur when a tropical fish suddenly finds itself in the Arctic? 1. Membranes are more rigid 2. Membranes are more fluid 3. 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 rigid 2. Membranes are more fluid 3. Membranes maintain the same fluidity 4. The organism dies 5. The organism survives 6. Membrane maintains function 7. Membrane loses function 8. Lipid composition changes 9. 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?)