Chang

Question 1

This is the initial acceptor of fatty acids during TAG synthesis

Answer 1

Glycerol Phosphate

Question 2

This enzyme catalyzes DHAP –> Glycerol Phosphate

Answer 2

Glycerol Phosphate Dehydrogenase

Question 3

Where is glycerol kinase enzyme present? (Glycerol Phosphate

Answer 3

liver ONLY

Question 4

This _____ contains a fatty acid and/or a steroid.

Answer 4

lipid

Question 5

Fatty acids make: ____, _____, ____

Answer 5

triacylglycerol
phospholipid
glycolipid

Question 6

Triacylglycerol is ____-based.

Answer 6

glycerol

Question 7

Phospholipids are ____ and ___ based.

Answer 7

glycerol based or sphingosine based

Question 8

Glycolipids are ___-based

Answer 8

sphingosine-based

Question 9

Glycerol-based phospholipids are called:

Answer 9

glycerophospholipids (phosphoglycerides)

Question 10

Phosphoglycerides are formed from:

Answer 10

Phosphatidic acid + alcohol

Question 11

Common phosphoglycerides

Answer 11

phosphatidyl serine; 
phosphatidylcholine;
phosphaethanolamine;
phosphatidylglycerol --> cardiolipin
SEGC

Question 12

Sphingosine based phospholipids: 1) and 2)

Answer 12

Sphingomyelin
Ceramide
Glycolipids (formed from ceramide)

Question 13

How to degrade sphingomyelin

Answer 13

First understand that serine contributes to making sphingomyelin.

Serine –> Sphingomyelin –> (enzyme: sphingomyelinase, a type of Phospholipase C) ceramide

Ceramide –> (enzyme: ceramidase) free FAs + sphingosine

Question 14

Nieman Pick Type A or B

Answer 14

Can’t degrade sphingomyelin due to not having sphingomyelinase

• Hepato/splenomegaly
• Cherry red macular spot (accumulation of sphingolipids)

Question 15

Phosphoglyceride degradation

Answer 15

Phospholipid –> (enzyme: Phospholipase A1, A2, C, or D) Lysophosphoglyceride

A2 can then produce arachadonic acid

Question 16

Structure of cholesterol

Answer 16

Sterol nucleus (4 rings) with 8-10 C’s at C17 and a hydroxyl at C3 (that’s what a sterol is)

Question 17

Does most plasma cholesterol exist in an esterified form?

a) Y
b) N

Answer 17

yes

Question 18

Where is cholesterol made?

Answer 18

all tissues but esp in liver, INTESTINE, adrenal cortex, reproductive tissues, and brain

Question 19

What is the pathway of cholesterol synthesis?

Answer 19

2 Acetyl CoA –> Acetoacetate –> HMG CoA Reductase –> Mevalonic acid –> 5’ pyrophosphomevalonic acid –> IPP –> DPP –> GPP –> FPP –> Squalene –> Lanosterol –> Cholesterol

Question 20

If you have a mutation in the enzyme that takes you from lanosterol to cholesterol, this is…
It’s the last precursor sterol.

Answer 20

enzyme: 7-dehydrocholesterol-7-reductase

Results in Smith-Lemli-Opitz syndrome

Question 21

Pathway of cholesterol BREAKDOWN

Answer 21

1) LDL binds LDL(r)
2) LDL(r) gets internalized and taken up - endosomes/lysosomes
3) Degradation in endo/lysosomes
4) apo-B100 degraded –> amino acids
cholesteryl esters degraded –> Free cholesterol + FAs
5) The free cholesterol moves either to the plasma membrane for membrane synthesis or to the ER to help out with regulation.
6) How does it do this? It downregulates SREBP and increases ACAT1

Question 22

In this disease, pts do not have functional LDL(R)

Answer 22

familial hypercholesteremia

Question 23

How can we regulate HMG-CoA-reductase?

Answer 23

1) Sterol-dependent transcriptional regulation:
low cholesterol –> high SREBP2 –> high HMG-CoA-Reductase –> Synthesize more cholesterol and Activate LDL(r) gene
2) Dihydrolanosterol (aka 27-hydroxycholesterol) -> decreases stability of HMG CoA Reductase –> Less cholesterol
3) Sterol-indep phosphorylation –> phosphorylation makes HMGR INACTIVE
4) Hormones –> high insulin = high activity HMGR
5) Drugs –> statins –> inhibit HMGCR

Question 24

tell me what happens w/statins.

Answer 24

Statins inhibit HMG-CoA Reductase
So low cholesterol –> high SREBP –> increase activity of LDL(R) b/c body thinks more cholesterol is coming –> more cholesterol is taken up –> less cholesterol in the blood

Question 25

major enzyme in cholesterol STORAGE in cells

Answer 25

ACAT-1

Question 26

isoforms of ACAT 1

Answer 26

ACAT1 - major one, prevents accumulation of cholesterol in the cell membrane
ACAT2:
These are NOT controlled by SREBP!

Question 27

This is the first intermediate in bile acid synthesis

Answer 27

7-alpha-hydroxy cholesterol

Question 28

This is involved in bile synthesis as an intermediate

Answer 28

25-hydroxycholesterol, made by cholesterol-25-hydroxylase.

Question 29

This is the most abundant oxysterol in the BRAIN!!!

Answer 29

24S-hydroxycholesterol
***Cholesterol-24-Hydroxylase is an enzyme that makes brain cholesterol more hydrophilic so that it can get across BBB to be excreted.

Question 30

This is the most abundant oxysterol in the BODY

Answer 30

27-hydroxycholesterol.

• responsible for sterol-mediated degradation of HMGR
• Made by Cholesterol 27 hydroxylase