Components, Structure and Control of Fluidity

Question 1

What fatty acid is commonly found in phospholipids?

Answer 1

Oleic Acid

Question 2

Why are double bonds found in fatty acids?

Answer 2

• reduce packing efficiency
• causing gaps between tails
• decreases fluidity
• affects Van der Waal forces

Question 3

Why are double bonds in lipid fatty acid tails rarely in the trans (E) configuration?

Answer 3

Double bonds are rarely in trans configuration as they would still be straight and not at a bend

Question 4

What are the three common head groups?

Answer 4

Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine

Question 5

What are glycolipids?

Answer 5

sugars containing lipids

Question 6

Name an example of a common glycolipid?

Answer 6

Sialic acid

• rich in epithelial cells
• viruses recognise these cells

Question 7

How do you work out the phase transition temperature (Tm)?

Answer 7

• measured by melting point to get liquid crystals

- from ordered gel phase to disordered liquid crystal phase

Question 8

What is the phase transition temp (Tm) dependent on?

Answer 8

Membrane components and their relative proportions

Question 9

Why is cholesterol important in the phospholipid bilayer?

Answer 9

• regulates membrane fluidity

- can modify properties

Question 10

What would happen to the melting point of phospholipid bilayers in the absence of cholesterol?

Answer 10

without cholesterol, sharp transition of melting point

Question 11

What sort of lipid being present would increase the MP/ Tm?

Answer 11

Saturated (double bonds) would give a higher temperature

Question 12

What is the need for membrane fluidity?

Answer 12

• phagocytosis
• pinocytosis (cell gets nutrients)
• receptor mediated endocytosis (way that a virus can get in)

Question 13

Why is a bilipid layer more stable than other lipid structures?

Answer 13

• it is flat

- the 2 tails make it more stable

Question 14

How are phospholipids delivered to the mitochondrial outer membrane?

Answer 14

Phospholipid exchange proteins are used to move the lipid from the ER membrane onto the mitochondrial membrane. When the lipid is bound to the protein it is transported through the cytosol into the mitochondrial outer membrane and the empty protein returns to the ER membrane.

Question 15

What do flippases do?

Answer 15

Move lipids from the external surface toward the cytosolic surface of the plasma membrane

Question 16

What are the different proteins present in the plasma membrane?

Answer 16

• protein channel
• inner surface integral membrane protein
• integral membrane protein
• peripheral protein
• single-pass alpha helical membrane protein

Question 17

What are the different lipid movement seen in plasma membranes?

Answer 17

Lateral movement
- extremely fast spontaneous
Lipid spinning
- extremely fast spontaneous-
Translocation
- moving lipids to the other side of the membrane
- extremely slow

Question 18

What are different ways to study membranes?

Answer 18

• microscopy with fluorescent markers
• structural biology
• vesicle studies
• bioinformatics

Question 19

What are the different techniques used to study lipids?

Answer 19

• phospholipase study
• TLC
• mass spec
• lipid extractions
• melting temps
• lipid structure simulations