Complex Lipids & Cholesterol Biochemistry Flashcards Preview

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Flashcards in Complex Lipids & Cholesterol Biochemistry Deck (22):
1

Cholesterol concentration is highly regulated in the ____________.

liver cells

2

____________ synthesize cholesterol.

Hepatocytes

3

In addition to synthesis, hepatocytes can also get cholesterol from ______________.

diet, HDL, and LDL

4

There is both cholesterol and cholesteryl esters. Where is each found and why?

Cholesterol: more soluble and so found in lipid membranes

Cholesteryl ester: less soluble and so found in plaques and other aggregates

5

Trace the cholesterol synthesis pathway.

2 x acetyl co-a
(Thiolase)
Acetoacetyl co-a
(HMG co-a synthase)
HMG co-a
(HMG co-a reductase) ***REGULATED STEP; USES 2 NADPH***
Mevalonic acid
Isopentenyl pyrophosphate
Geranyl pyrophosphate
Farnesyl pyrophosphate
Squalene
Lanosterol
Cholesterol

6

Expression of HMG co-a reductase is controlled by ___________.

SREBP, which is a protein that binds SRE (the region of DNA that encodes for HMG co-a)

7

How is SREBP controlled?

It is sequestered in the Golgi. When cholesterol is high, SREBP is prevented from leaving the ER. When cholesterol is low, SREBP is allowed to leave the ER and promote synthesis of HMG co-a reductase by binding to the SRE gene.

8

What does Dr. Bessesen want us to know about phospholipids?

Be able to recognize their names (like phosphatidylserine) and know that they are made from a glycerol backbone.

9

Glycolipids have a _____________ backbone.

ceramide

10

Where are glycolipids prominent?

In the nervous system (such as cerebroside)

11

Deficiencies in ___________ will produce accumulation of lipids in the nervous system.

lysosomal hydrolase

12

Cholesterol is a precursor for vitamin _____ in addition to bile acids and steroid hormones.

D

13

How much cholesterol do people typically eat per day?

300 - 600 mg (we synthesize about 1,000 mg)

14

HMG co-a is synthesized from ___________.

acetyl co-a

15

Other than cholesterol levels in the cytosol of hepatocytes, what additional mechanism regulates HMG co-a reductase?

Insulin increases its transcription and glucagon decreases its transcription.

16

Cholesterol also regulates the ________ of HMG co-a reductase.

half-life

17

AMP kinase is stimulated by AMP. What does it do?

It phosphorylates HMG co-a reductase and thus inactivates it.

18

The statins are analogues of ___________.

mevalonate (the product of HMG co-a reductase) and thus act as competitive inhibitors of HMG co-a reductase

19

____________ is the main class of lipids that make up the lipid membrane.

Glycerophospholipids (the two most common are phosphatidylcholine and phosphatidylethanolamine)

20

_______________ serves as a reservoir for arachidonic acid.

Phosphatidylinositol

21

The sugars added to glycolipids are added in the _______ form.

UDP-glucose

22

What does IP3 do?

It binds to ER calcium channels, opens them, and then that intracellular calcium activates PKC.

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