Membrane structure and function II Flashcards
What are the function of membranes? [3 marks]
- Transport
- Intracellular compartmentalisation
- Cell-cell recognition
What functions does the plasma membrane carry out? [3 marks]
- Barrier
- Transport
- Signal transduction
What functions does the inner membrane carry out? [1 mark]
Energy transduction
What functions does the endoplasmic reticulum carry out? [2 mark]
ROUGH: Translation protein processing
SMOOTH: Synthesis of complex lipids
What functions does the Golgi apparatus carry out? [2 marks]
- Post translational modification
- Processing for secretion
What do lysosomes contain? [1 mark]
Hydrolytic enzymes
What function do peroxisomes carry out? [1 mark]
Fatty acid oxidation
What is myelin and what does it do? [3 marks]
- Consists mainly of lipids
- Insulates axons
- Facilitates saltatory conduction
What is the difference in structure between the outer and the inner mitochondrial membrane? [2 marks]
OUTER: equal amounts of proteins and lipids
INNER: Made mostly of proteins (especially ATPase)
What does it been when carrier proteins are saturated? [1 mark]
Means that there are more molecules to be transported than carrier proteins available.
What does a uniporter do? [1 mark]
Carries one molecule at a time.
What does an antiporter do? [1 mark]
Carries 2 molecules in opposite directions.
What does a symporter do? [1 mark]
Carries 2 molecules in the same direction.
What is the structure of glucose transporters? [1 mark]
12 transmembrane domains
Where is GLUT1 founded? [3 marks]
- In fetal tissues
- In erythrocytes and blood-brain barrier
- LOW Km
Where is GLUT2 founded? [3 marks]
- In liver
- In pancreatic beta cells
- HIGH Km
Where is GLUT3 founded? [3 marks]
- In neurones
- In placenta
- LOW Km
Where is GLUT4 founded? [3 marks]
- In adipocytes
- In skeletal muscle
- LOW Km
What is GLUT4 stimulated by? [2 marks]
- By insulin
- Increase the uptake of glucose by GLUT4
Mechanisms of membrane transport facilitated diffusion [3 marks]
- Confirmational change of carrier results in transportation.
- Driven by bidrectional concentration gradient.
- Gradient maintained by phosphorylation: when glucose is phosphorylated, it leaves GLUT.
How does foxglove (digitalis) alleviate symptoms of congestive heart disease? [5 marks]
- 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.
Where are sodium dependent glucose transporter (SGLUT1/SGLUT2) located? [1 mark]
The lining of the gut.
How does rehydration therapy help with dehydration? [2 marks]
- Targets the co-transport of glucose and sodium with SGLUT.
- It also has an osmotic effect (draws in water).
What happens in cystic fibrosis? [2 marks]
- Caused by single amino acid change in gene for cystic fibrosis transmembrane conductance regulator.
- CFTR functions as a Cl- channel.
