Lecture 1.3 - Lipid synthesis, membrane formation, width, and formation

Question 1

Phospholipid synthesis: where does it start and what is the process?

Answer 1

Cytosolic leaflet of the ER

G3P + Acyl CoA -> Lysophosphaditate + CoA

Lysophosphadidate + Acyl CoA -> Phosphaditate + CoA

Enzyme for this process glycerol phosphate acyl transferase

Phosphaditate is the base for all the phospholipids to be formed from

Question 2

Phospholipid synthesis: how does phosphaditate form lipids?

Answer 2

Phosphaditate + CTP -> CDP-Diacylglycerol + PP

CDP-diacylglycerol can then react with serine or inositol, etc

To then form with choline or ethanolamine, phosphatidylserine needs to be made and then undergo reactions to form phosphatidylethanolamine and then phosphatidylcholine

(The production of phosphatidylserine/inositol will result in the production of CMP)

Question 3

Leaflets of membranes: what are they?

Answer 3

Cytosolic (outer) leaflet - typically has less curvature, faces the cytosol

Luminal (inner) leaftlet - typically has more curvature, faces towards the inner components within the membrane

Question 4

Where are lipids made?

Answer 4

Sterols - Luminal leaflet of ER

Glycerophospholipids - cytosolic leaflet of ER

Sphingolipids - Begins in the cytosolic leaflet of Golgi, ends in the luminal

Question 5

Sphingolipid production

Answer 5

Mainly occurs in the ER

Condensation of L-serine and palmotyl CoA - catalysed by serine palmotyltransferase

This forms dehydrosphingosine which is then reduced by NADPH first and then FAD afterwards to form sphingosine

Question 6

What is palmotyl CoA formed from?

Answer 6

Palmytic acid

Question 7

SO MUCH BIOCHEMISTRY

Answer 7

Come back if have time

Question 8

Cholesterol: how does it affect membrane fluidity?

Answer 8

Makes membranes less rigid, interacts with hydrophobic region of phospholipids