Complex Lipids & Cholesterol Biochemistry

Question 1

synthesis of cholesterol occurs in the ______ of the cell

Answer 1

cytosol

Question 2

cholesterol Occurs in 2 forms: _______

Answer 2

free cholesterol (amphipathic) and cholesterol esters (non-polar)

Question 3

• The liver is the major site of cholesterol synthesis, but the __________ also synthesize cholesterol to make steroid hormones

Answer 3

adrenal cortex, the ovaries and the testes

Question 4

The second step of cholesterol syntheisi is the conversion of HMG CoA to mevalonic acid (mevalonate) by _______ . This is the rate limiting step in this pathway and is the key regulated step. This reaction occurs in the cytosol and uses NADPH as the reducing agent.

Answer 4

HMG CoA reductase

Question 5

geranyl pyrophosphate and farynyl pyrophosphate are in what pathway?

Answer 5

Cholesterol biosynthesis

Question 6

how is HMG CoA Reductase regulated?

Answer 6

1) Regulation of gene expression by SREBP
2) Regulation by degradation of enzyme
3) Phosphorylation of enzyme by AMP activated protein kinase: High AMP inactivates enzyme
4 Hormonal regulation by insulin/glucagon
transcriptional

Question 7

Arachidonic acid can also be converted to leukotrienes via the enzyme _______

Answer 7

5-lipoxygenase

Question 8

what are Glycerophospholipids

Answer 8

main class of phospholipids and makes up the bulk of membrane lipids. The backbone comes from phosphatidic acid which is a precursor in triglyceride biosynthesis. Then the head group is added. Examples include phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Each of these is named for the structure of the polar head group

Question 9

The polar head groups of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are formed de novo or come from the diet, they are then activated by _____, then attached to the backbone

Answer 9

CDP

Question 10

what is the main component in lung surfactant

Answer 10

Phosphatidylcholine

Question 11

name the lipid that Serves as a reservoir for arachidonic acid which is used in prostaglandin synthesis

Answer 11

Phosphatidylinositol

Question 12

Describe sphingomyelin

Answer 12

• Has a sphingosine/ceramide backbone, and a choline head group
• Major structural lipid in nerve tissue
• The precursor to this lipid is ceramide made from a fatty acid and an amino acid (serine).

Question 13

This type of lipid is found primarily in the brain and peripheral nerves
• Examples include cerebroside, globoside and gangliosides.

Answer 13

Glycolipids, (glycosphingolipids)

Question 14

what is Another pathway for synthesis of Glycerophospholipids besides CDP

Answer 14

“base exchange” whereby the head-groups are exchanged onto previously synthesized phospholipids.