Membrane Bylayer-biophysical Properties

Question 1

What are the general functions of biological membranes?

Answer 1

Continuous highly selective permeability barrier
Control enclosed chemical environments 
Communication 
Recognition of molecules 
Signal generation

Question 2

What is a membrane approximately made up of?

Answer 2

40% lipid
60% protein
1-10% carbs

Question 3

Define amphipathic molecules.

Answer 3

Contain both a hydrophilic and hydrophobic Moiety (Eg membrane lipids)

Question 4

What is a cerebroside?

Answer 4

A glycolipid that has a monosaccharide sugar attached.

Question 5

What is a ganglioside?

Answer 5

A glycolipid that has an oligosaccharide sugar attached.

Question 6

Which parts of the lipid are hydrophilic/phobic?

Answer 6

Head is hydrophilic _ make up outside f membrane

Tail is hydrophobic_make up inside of membrane

Question 7

How can phospholipids move in the membrane?

Answer 7

Flexion
Rotation
Lateral diffusion
Flip flop (rarer)

Question 8

What do the cis double bonds in phospholipids cause and why is this helpful?

Answer 8

They cause a kink in the molecule.

This reduces phospholipid packing making it easier for lipids to move in the membrane

Question 9

What is the structure of cholesterol?

Answer 9

A polar head group
Rigid planar steroid ring
Non-polar hydrocarbon tail

Question 10

What effect does putting cholesterol in the phospholipids membrane have?

Answer 10

It means the layer takes in less energy so doesn’t melt and become really flexible.
It increase stability

Question 11

How is cholesterol inserted into the phospholipid bylayer?

Answer 11

It form h bonds with the phospholipids side chains

Question 12

How does cholesterol effect phospholipid fluidity in both directions?

Answer 12

Increases it as it reduces packing

Decreases it by reducing chain motion