Glycerolipid and Sphingolipid Metabolism

Question 1

What is CDP-diacylglycerol a precursor of?

Answer 1

A precursor of the various glycerophospholipids.

Question 2

What is phosphatidic acid a precursor of?

Answer 2

An immediate precursor of CDP-diacylglycerol

Question 3

CTP combines with phosphatidic acid to yield what?

Answer 3

a pyrophosphate and CDP-Diacylglycerol

Question 4

Activation by CDP yields what?

Answer 4

a high energy activated intermediate that can be readily converted to phosphatidyl glycerophospholipids

Question 5

Phosphatidyl serine, phosphatidyl ethanolamine, and phosphatidyl choline can be make from what?

Answer 5

CDP-diacylglycerol

Question 6

Synthesis of phosphatidyl choline from phosphatidyl ethanolamine requires what?

Answer 6

Methyl groups donated by S-Adenoysyl-Methionine (SAM).

Question 7

Loss of the methyl groups by SAM yields:

Answer 7

S-Adenosyl-Homocysteine

Question 8

What two things can both be made independently of phosphatidic acid biosynthesis?

Answer 8

Phosphatidyl ethanolamine and phosphatidyl choline - derived from phosphatidyl ethanolamine

Question 9

How are these made independently of phosphatidic acid biosynthesis?

Answer 9

CDP-ethanolamine is the activated intermediate and the phosphoethanolamine of it is added to diacylglycerol to form phosphatidyl ethanolamine.

Question 10

Sphingolipids are synthesized beginning with:

Answer 10

palmitoyl-CoA and serine

Question 11

Addition of a fatty acid to the amine group of a sphingolipid yields a _____. Addition of sugars to a ceramide yields either a ______ (single sugar added) or a _______ (complex sugar added).

Answer 11

• ceramide
• cerebroside
• ganglioside

Question 12

Deficiencies in enzymes that degrade sphingolipids (particularly cerebrosides and gangliosides) are linked to:

Answer 12

Neural Disorders, such as Tay Sachs disease.

Question 13

Cholesterol can be synthesized totally from:

Answer 13

Acetyl CoA

Question 14

Steroids include all compounds synthesized from cholesterol. This includes:

Answer 14

steroid hormones, vitamin D, bile acids, and other related compounds.

Question 15

Isoprenes/Isoprenoids:

Answer 15

5 carbon units containing isopentenyl pyrophosphate and dimethylallyl pyrophosphate

Question 16

isopentenyl pyrophosphate and dimethylallyl pyrophosphate are made from what?

Answer 16

acetyl-CoA molecules

Question 17

Isoprenes (also called isoprenoids) include the steroids and other compounds, such as:

Answer 17

Vitamin A and E that are also made from isoprene units.

Question 18

Synthesis of isopentenyl pyrophosphate and dimethylallyl pyrophosphate comes from _____, which, in turn, comes from ______, so isoprenoid biosynthesis overlaps partly with _______.

Answer 18

• mevalonate
• HMG-CoA
• ketone body synthesis

Question 19

The most important enzyme in cholesterol biosynthesis is:

Answer 19

HMG-CoA reductase

Question 20

What does HMG-CoA reductase do? What does is the enzyme inhibitor?

Answer 20

It converts HMG-CoA to mevalonate and is the primary regulatory enzyme in cholesterol biosynthesis. Cholesterol is a feedback inhibitor of the enzyme.

Question 21

Reaction of isopentenyl pyrophospahte with dimethylallyl pyrophosphate yields:

Answer 21

10-carbon intermediate, geranyl pyrophosphate

Question 22

Reaction of geranyl pyrophosphate with isopentenyl pyrophosphate yields:

Answer 22

15 carbon intermediate - farnesyl pyrophosphate.

Question 23

Reaction of two farnesyl pyrophosphates yields:

Answer 23

a 30 carbon intermediate - squalene.

Question 24

Further reaction of squalene yields:

Answer 24

a cyclic intermediate, lanosterol

Question 25

From cholesterol, one can synthesize the _____ _____ (glycocholate and taurocholate, among others), which are useful in solubilizing ___ in the diet. Cholesterol also leads to synthesis of the ______ _____.

Answer 25

- Bile salts - fat - steroid hormones

Question 26

SREBP (Steroid response element binding protein) is a protein that plays a role in:

Answer 26

controlling whether or not HMG-CoA reductase is made.

Question 27

Three components of the SREBP as "R" -regulatory (binds to _____), "M" - _______, and "D" - DNA binding portion. ____ refers to a region of DNA bound by the ___ portion of SREBP.

Answer 27

- SCAP - membrane portion - SRE - D

Question 28

When cholesterol levels in the cell fall, the SREBP-ER complex:

Answer 28

moves to the golgi complex. The serine protease in the golgi cleaves the SREBP-G to release the MD regions.

Question 29

After the MD portions of SREMP-G are released:

Answer 29

They migrate in the membrane to a metalloprotease which clips and frees the D region from the M region.

Question 30

After the M and D portions separate:

Answer 30

the D region travels through the cytoplasm to the nucleus. It binds to a promoter region in front of HMG coA Reductase and other genes with an SRE.

Question 31

What does the binding of the D region to the promoter region cause?

Answer 31

HMG-CoA reductase to be synthesized and cholesterol synthesis to begin.