Lipids & Membranes

Question 1

What are the TWO basic properties of biomembranes?

Answer 1

1. Impermeable to water-soluble solutes
2. Extremely stable

Question 2

How thick is a lipid bilayer?

Answer 2

3-5nm

Question 3

TRUE OR FALSE:
Membrane lipids are amphipathic?

Answer 3

True.
* Polar Head - hydrophilic
* Non-polar Tail - hydrophobic

Question 4

What is the basic structure of a Glycerophospholipid?

Answer 4

• 3x Carbon groups
• 2x Fatty Acid tails
• 1x Phosphate group

Question 5

TRUE OR FALSE:
Both FA tails on a Glycerophospholipid are saturated fatty acids?

Answer 5

False.
There is 1x SATURATED (no double bond) and 1x UNSATURATED (double bond) FA

Question 6

What is the basic structure of a Sphingolipid?

Answer 6

• Sphingosine backbone
• Fatty acid attached via amide link to C2

Question 7

Where are Sphingolipids likely to be found in the body?

Answer 7

ABO blood groups

Question 8

A defect in a lysosomal enzyme Hexosaminidase A causes which disease?

Answer 8

Tay-Sachs Disease

Question 9

A defect in the Sphingomyelinase enzyme causes which disease?

Answer 9

Niemann Pick Disease

Question 10

What is the basic structure of a sterol?

Answer 10

• 3x 6-sided ring
• 1x 5-sided ring

Question 11

What types of FA chains INCREASE membrane fluidity?

Answer 11

• Unsaturated fatty acyl chains
• Short fatty acyl chains

Question 12

What type of FA DECREASES membrane fluidity?

Answer 12

Sterols (Cholesterol in animals)

Question 13

Which lipid types are most commonly found in Lipid Rafts?

Answer 13

Sphingolipids & Cholesterol

Question 14

Which proteins are most commonly found in Lipid Rafts?

Answer 14

• GPI-linked proteins
• Doubly acylated proteins

Question 15

What are TWO possible functions of Lipid Rafts?

Answer 15

1. Concentrate certain proteins/lipids together
2. Transmembrane signalling

Question 16

What causes asymmetric distribution of lipids in monolayers?

Answer 16

1. Site of Synthesis
2. Action of Flippases

Question 17

Where is Sphingomyelin synthesised?

Answer 17

Luminal (ectoplasmic) face of Golgi

Question 18

Where are Phosphoglycerides synthesised?

Answer 18

Cytosolic face of ER

Question 19

What are the TWO forms of diffusion of Phospholipids in membranes?

Answer 19

1. Transverse (Flip Flop)
2. Lateral

Question 20

Is Transverse Diffusion a fast or slow process?

Answer 20

Slow

Question 21

Is Lateral Diffusion a fast or slow process?

Answer 21

Fast

Question 22

TRUE OR FALSE:
Transverse diffusion can be catalysed by Flippases?

Answer 22

True

Question 23

TRUE OR FALSE:
Only the Plasma Membrane has cytosolic and exoplasmic faces?

Answer 23

False.
Both the PM and internal membranes have cytosolic and exoplasmic faces

Question 24

Is the orientation of the cytosolic and exoplasmic faces maintained or changed during membrane trafficking?

Answer 24

It is maintained

Question 25

Which areas of the cell are equivalent?

Answer 25

• Extracellular space
• Lumen of Golgi, ER, Lysosome
• Intermembrane space of Nuclear Envelope, Mitochondria, Chloroplasts