Chapter 6 Part 2: Membrane Permeability

Question 1

What types of things are very permeable in a phospholipid bilayer?

Answer 1

1. ) small non-polar molecules.

2. ) small, uncharged polar molecules

Question 2

What types of things are not very permeable in a phospholipid bilayer?

Answer 2

1. ) small ions

2. ) large uncharged polar molecules

Question 3

What does the permeability of a membrane depend on?

Answer 3

it’s fluidity.

Question 4

What is the movement pattern of phospholipids within the membrane?

Answer 4

• Phospholipids move around on the leaflet it is located on.

Question 5

What happens to the permeability of the membrane as the speed of phospholipid movement per leaflet increases?

Answer 5

permeability increases

Question 6

What is fluidity of the degree of?

Answer 6

van der Waals interactions.
More interactions = stiffer, less fluidity, less permeable membrane
Less interactions = looser, more fluid, more permeable

Question 7

When do Van Der Waals interactions occur?

Answer 7

They occur between nonpolar molecules

Question 8

What environmental factors affect the permeability of phospholipid bilayers?

Answer 8

• factors that impact the degree of van der waals interactions:
• increase in pressure
• decrease in temperature
• length of hydrocarbon chains on phospholipid fatty acid chains.
• saturated vs unsaturated phospholipid fatty acid chains.
• amount of sterols

Question 9

What does the length of the fatty acid/ or tail of the phospholipid equate to?

Answer 9

shorter the tail the more fulidity.

Question 10

What does the saturation of the fatty acid chain equate to?

Answer 10

More saturated the less fluidity

Question 11

What are the structural differences between unsaturated and saturated fatty acids?

Answer 11

Unsaturated has a C–C carbon to carbon double bond in the center, and contains less hydrogen molecules.
- The double bond puts a kink in the fatty acid.
- This preventing the tightness of the phospholipid bilayer.
Saturated:

Question 12

What characteristics of membranes equate to a a higher and lower permeability?

Answer 12

Higher- lipid bilayer with short and unsaturated hydrocarbon tails.
Lower- lipid bilayer with long saturated hydrocarbon tails.

Question 13

What do sterols do to the permeability of the membrane?

Answer 13

sterols tend to decrease membrane fluidity.