The Cell Membrane

Question 1

What are the 4 factors affecting fluidity?

Answer 1

Temperature, presence of double bond, fatty acid tail length, presence of cholesterol in the membrane.

Question 2

What is the Cell Membrane?

Answer 2

Selective and dynamic cell boundary and separates the cell from its aqueous environment, it maintains the integrity of the cell. It has key roles involving the passage of molecules and ions into and out of the cell. Includes the lipid bilayer.

Question 3

What is the Fluid Mosaic ‘framework’?

Answer 3

A semi fluid phospholipid bilayer with a mosaic of proteins. This also has some carbohydrates that may be attached to lipids or proteins within the lipid bilayer.

Question 4

Structure of membrane lipids and molecules?

Answer 4

Membrane lipids are held together by weak intermolecular forces rather than stronger covalent bonds. The molecules in the membrane exchanges places millions of times in a single second leading to a continual rearrangement of the membrane surfaces. Ex: a puncture in the membrane will result in molecules quickly rearrange to seal the puncture.

Question 5

Viscosity of membrane at room temperature?

Answer 5

At room temperature your cell membrane tends to have the viscosity similar to vegetable oil. Too fluid can mean too much diffusion and not fluid enough means it may not allow things it needs to diffuse through.

Question 6

Temperature

Answer 6

Increased temperature increases fluidity and could lead it to be unable to act as a suitable barrier; Decreasing temperature it can become more gel like and become too much of a barrier preventing items from moving well.

Question 7

Presence of Double Bonds

Answer 7

The more double bonds that occur the less tightly packed and therefor the more fluid.

Question 8

Fatty Acid Tail Length

Answer 8

Longer tails have more intermolecular attractions and hold together more tightly compared to shorter fatty acids and therefor reduce fluidity

Question 9

Presence of Cholesterol

Answer 9

The presence of cholesterol in the membrane, at room
temperature the higher the presence the more forces in the membrane and it will hold more tightly together so reduce fluidity, but if the temperature is lower the cholesterol molecule breaks up and the phospholipids may start to “gel up” but the cholesterol breaking up helps to make it more fluid.