Membrane structure and function II

Question 1

What are the function of membranes? [3 marks]

Answer 1

• Transport
• Intracellular compartmentalisation
• Cell-cell recognition

Question 2

What functions does the plasma membrane carry out? [3 marks]

Answer 2

• Barrier
• Transport
• Signal transduction

Question 3

What functions does the inner membrane carry out? [1 mark]

Answer 3

Energy transduction

Question 4

What functions does the endoplasmic reticulum carry out? [2 mark]

Answer 4

ROUGH: Translation protein processing
SMOOTH: Synthesis of complex lipids

Question 5

What functions does the Golgi apparatus carry out? [2 marks]

Answer 5

• Post translational modification

- Processing for secretion

Question 6

What do lysosomes contain? [1 mark]

Answer 6

Hydrolytic enzymes

Question 7

What function do peroxisomes carry out? [1 mark]

Answer 7

Fatty acid oxidation

Question 8

What is myelin and what does it do? [3 marks]

Answer 8

• Consists mainly of lipids
• Insulates axons
• Facilitates saltatory conduction

Question 9

What is the difference in structure between the outer and the inner mitochondrial membrane? [2 marks]

Answer 9

OUTER: equal amounts of proteins and lipids
INNER: Made mostly of proteins (especially ATPase)

Question 10

What does it been when carrier proteins are saturated? [1 mark]

Answer 10

Means that there are more molecules to be transported than carrier proteins available.

Question 11

What does a uniporter do? [1 mark]

Answer 11

Carries one molecule at a time.

Question 12

What does an antiporter do? [1 mark]

Answer 12

Carries 2 molecules in opposite directions.

Question 13

What does a symporter do? [1 mark]

Answer 13

Carries 2 molecules in the same direction.

Question 14

What is the structure of glucose transporters? [1 mark]

Answer 14

12 transmembrane domains

Question 15

Where is GLUT1 founded? [3 marks]

Answer 15

• In fetal tissues
• In erythrocytes and blood-brain barrier
• LOW Km

Question 16

Where is GLUT2 founded? [3 marks]

Answer 16

• In liver
• In pancreatic beta cells
• HIGH Km

Question 17

Where is GLUT3 founded? [3 marks]

Answer 17

• In neurones
• In placenta
• LOW Km

Question 18

Where is GLUT4 founded? [3 marks]

Answer 18

• In adipocytes
• In skeletal muscle
• LOW Km

Question 19

What is GLUT4 stimulated by? [2 marks]

Answer 19

• By insulin

- Increase the uptake of glucose by GLUT4

Question 20

Mechanisms of membrane transport facilitated diffusion [3 marks]

Answer 20

• Confirmational change of carrier results in transportation.
• Driven by bidrectional concentration gradient.
• Gradient maintained by phosphorylation: when glucose is phosphorylated, it leaves GLUT.

Question 21

How does foxglove (digitalis) alleviate symptoms of congestive heart disease? [5 marks]

Answer 21

• Inhibits the Na+/K+ pump.
• Concentration of Na+ increases and stimulates the Na+/Ca2+ exchanger.
• Na+/Ca2+ exchanger is an antiporter, so Na+ is pumped out and Ca2+ is pumped in.
• Heart uses Ca2+ in a positive feedback loop to trigger contraction.
• Improves contractibility.

Question 22

Where are sodium dependent glucose transporter (SGLUT1/SGLUT2) located? [1 mark]

Answer 22

The lining of the gut.

Question 23

How does rehydration therapy help with dehydration? [2 marks]

Answer 23

• Targets the co-transport of glucose and sodium with SGLUT.

- It also has an osmotic effect (draws in water).

Question 24

What happens in cystic fibrosis? [2 marks]

Answer 24

• Caused by single amino acid change in gene for cystic fibrosis transmembrane conductance regulator.
• CFTR functions as a Cl- channel.