Topic 4

Question 1

Fluid mosaic model

Answer 1

• Current view of membrane structure is based on the fluid mosaic model.
• The model proposes that membranes are not rigid with molecules locked into place.
• Rather, the membrane consists of proteins that move around within a mixture of lipid molecules that has the consistency of olive oil.

Question 2

What is the evidence for the fluid mosaic model of membrane structure?

Answer 2

1. Membranes are fluid
2. Membrane Asymmetry

Question 3

What is meant by the term membrane asymmetry?

Question 4

What’s the experimental evidence for the fluidity of membranes?

Question 5

What’s the experimental evidence for membrane asymmetry?

Question 6

What is meant by membrane fluidity?

Question 7

What are the three main things cell membranes made up of?

Answer 7

• phospholipids
• cholesterol
• proteins

Question 8

Phospholipid

Answer 8

• ## Lipid that involves a phosphate group

Question 9

How does low temperature affect membrane fluidity?

Answer 9

• Low temperature = the random molecular motion of lipid molecules slows down.
• phospholipids close together
• Fluidity is lost, and the phospholipid molecules form a semisolid gel.
• low temp = motion slows = fluidity low = semisolid gell

Question 10

Saturated fatty acids

Answer 10

• all carbons have maximum hydrogen atoms.

Question 11

Unsaturated fatty acids

Answer 11

• contains a carbon-carbon double bond, making it unsaturated.
• C-C double bond causes a kink or bend in the unsaturated fatty acid tail.

Question 12

Temperature and gelling

Question 13

What are two factors that influence membrane fluidity?

Answer 13

• the type of fatty acids that make up the lipid molecules (unsaturated or saturated)
• the temperature

Question 14

How do saturated fatty acids affect membrane fluidity?

Answer 14

• Fully saturated fatty acids are linear, which allows lipid molecules to pack tightly together.
• Low fluidity - limited space for movement and rotation.

Question 15

Cholestrol

Answer 15

• cholestrol is a sterol

Question 16

How do sterols affect membrane fluidity?

Answer 16

• sterols act as membrane buffers
• sterols influence membrane fluidity
• at high temperatures sterols restrain the movement of lipid molecules. - reduces fluidity of the membrane.
• low temperatures: sterols disrupt fatty acids

Question 17

Where are cholesterol’s found?

Answer 17

• Cholesterol is found in the membranes of animal cells.

Question 18

How do unsaturated fatty acids affect membrane fluidity?

Answer 18

• Lipid molecules with unsaturated fatty acids can’t pack closely together due to carbon-carbon double bonds.
• The more unsaturated the fatty acids of the lipid molecules, the more fluid (less viscous) the membrane.
• more saturated = more fluidity because more space for movement.

Question 19

How does high temperature affect membrane fluidity?

Answer 19

• fluidity high
• more temperature = more energy so phospholipids have more distance in between them.

Question 20

What are the four functional categories for membrane proteins

Question 21

What are the two major classes of membrane proteins?

Question 22

Passive transport

Question 23

Diffusion

Question 24

Concentration gradient

Question 25

Simple diffusion

Question 26

Facilitated diffusion

Question 27

What two transport proteins aid in facilitated diffusion?

Answer 27

-

Question 28

Channel proteins