Membrane

Question 1

What are the different types of phosphoglycerides?

Answer 1

1. Phosphotydylethanolamine
2. Phosphotydylcholine
3. Phosphotydylserine
4. Phosphotydylinositol

Question 2

What makes up a sphingolipid?

Answer 2

Long carbon chain with 2 OH and 1 NH2 group at the end (sphingosine). R groups that interact with the amine and hydroxyl groups determine name and function.

Question 3

As the amount of cholesterol increases in a lipid, what happens to the fluidity of the membrane?

Answer 3

Fluidity decreases as Cholesterol increases.

Question 4

What effect does cholesterol have on the thickness of the membrane? Why does this happen?

Answer 4

More cholesterol=thicker membrane

This happens because cholesterol tends to straighten out the lipid chains of phospholipids.

Question 5

How do SCAP, SREBP, and Insig signal for cholesterol synthesis?

Answer 5

1. When Cholesterol is Low, the SCAP-SREBP-Insig complex breaks apart.
2. SCAP-SREBP go to the Golgi
3. the bHLH transcription factor is released from SREBP by RIP (regulated intramembrane proteolysis)
4. RIP is performed by S1P and S2P.
5. Transcription factor binds to DNA promoters for cholesterol synthesis

Question 6

Which phospholipid would you most likely expect to find on the exoplasmic face?

Answer 6

Phosphotydylcholine (PC)

All others (PE, PI, PS) are on the cytoplasmic face.

*Keep your Pi-pe-s on the inside.

Question 7

What is the association of Insig, SREBR, SCAP during High cholesterol times?

Answer 7

Insig is bound to SCAP

Question 8

What is the association of Insig, SREBR, SCAP during low cholesterol times?

Answer 8

Insig dissociates from SCAP and SCAP cleaves SREBP. SREBP enters in the Golgi.