Membrane Structure and Function

Question 1

5 features of all membranes

Answer 1

1. Flexible
2. Self-sealing
3. Selectively Permeable
4. They define boundaries
5. They divide internal spaces

Question 2

4 functions of membranes defined by their molecular composition

Answer 2

1. Transport
2. Cell recognition
3. Cellular Communication
4. Metabolic regulation

Question 3

Meaning of amphipathic

Answer 3

Hydrophilic and hydrophobic part included

Question 4

Where does synthesis of the phospholipid take place

Answer 4

Cytoplasmic surface of the membrane

Question 5

How are phospholipids transported from one side of the membrane to the other

Answer 5

Use ABC transporter (ATP Binding cassette transporters), enable movement of highly charged head group across hydrophobic region.

Question 6

Which 3 enzymes are used in phospholipid distribution, and what type of movement do they promote

Answer 6

1. Floppase - Inner to outer leaflet
2. Flippase - Outer to inner leaflet
3. Scramblase - Bidirectional

Question 7

5 factors that affect membrane fluidity

Answer 7

1. Temperature
2. Fatty acid composition
3. Chain length
4. Degree and extent of saturation
5. Cholesterol content

Question 8

How does temperature affect membrane fluidity

Answer 8

As temp increases, energy associated with phospholipid molecules will increase, and so will their movement

Question 9

How does fatty acid composition affect membrane fluidity

Answer 9

More unsaturated fatty acids are bent, making molecules less compact and therefore increased fluidity

Question 10

How does cholesterol content affect membrane fluidity

Answer 10

At lower temperatures, cholesterol increases fluidity due to reduced covalent lipid interactions.

At high temperatures, molecules have more energy and move more. The cholesterol helps stabilise the membrane by maintaining interactions.

Question 11

What happens in spur cell anaemia and what is it’s effect

Answer 11

Cholesterol content increases by 25-65%, leading to decreased membrane fluidity. The cells can then get trapped and rupture.

Question 12

4 features of integral membrane proteins

Answer 12

1. Single or multi pass
2. Strong non-covalent bonds
3. Trans-membrane domain often an alpha helix
4. Can be predicted from sequence

Question 13

Features of the peripheral membrane proteins

Answer 13

1. Located on both the extracellular cytosolic membrane
2. Associated by non-covalent bonds

Question 14

Name a membrane protein other than the integral or peripheral proteins

Answer 14

Lipid anchored membrane protein (has COVALENT bond to lipid molecule)

Question 15

State the interactions of the integral and peripheral proteins

Answer 15

1. Integral proteins interact with the lipid bilayer
2. Peripheral proteins interact with integral proteins or lipid polar head groups

Question 16

State the amount and functions of membrane carbohydrates in membranes

Answer 16

1. Forms 2-10% of membrane weight
2. Involved in cell-cell interactions or cellular recognition.

Question 17

What type of molecule are blood group antigens?

Answer 17

Glycolipids