Lipid Metabolism Flashcards Preview

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Flashcards in Lipid Metabolism Deck (37)
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1
Q

The majority of carbons that contribute to FA synthesis come from where?

A

-carbohydrates that are ingested, and undergo the first few steps of glycolysis. Specifically form DHAP or G3P

2
Q

Where is FA synthesis most common in occurring?

A

brain, liver, kidneys and are stored in adipocytes

3
Q

In the cells where does FA synthesis occur?

A

cytoplasm

4
Q

What are the starting units and the addition units of FA synthesis?

A
  • starts with acetyl CoA

- Malonyl CoA contributes 2 C additions to the growing FA chain

5
Q

What is the primary electron carrier that is used?

A

NADP+—–> NADPH

6
Q

What is the committed/rate limiting step in FA synthesis?

A

conversion of Acetyl CoA to Malonyl CoA via acetyl CoA carboxylase

7
Q

What are the 3 steps in FA synthesis?

A

Conversion of Acetyl CoA to Malonyl CoA

  • Elongation
  • Desaturation
8
Q

The elongation step of FA synthesis is what?

A

-malonyl CoA donates 2 C’s to the growing FA chain

9
Q

What is the point of a desaturation reaction with FA synthesis?

A

this process allows for the addition of double bonds to the chain

10
Q

What is the coenzyme for carboxylases?

A

-biotin

11
Q

After the TCA cycle, citrate is produced and can be used to produce what components?

A
  • supply C’s for FA synthesis

- use of citrate lyase to from Acetyl CoA

12
Q

What enzyme is used to convert Acetyl CoA to Malonyl CoA?

A

acetyl CoA carboxylase (ACC)

13
Q

What factors with increase or promote the activity of ACC?

A
  • citrate
  • insulin
  • high carb/low fat diet
  • available amount of B7—> biotin (which is cofactor for carboxylases)
14
Q

What factors with inhibit the activity of ACC?

A
  • [Long chain FA]
  • epinephrine/glucagon (signal energy burning)
  • low carb/ high fat diet
  • deficiency of Vit. B7
15
Q

What ways is the ACC regulated?

A
  • phosphorylation pathways
  • allosteric pathways
  • gene expression pathways
16
Q

Fatty acid synthase is the enzyme where FA synthesis occurs. What is the structural components that allow this?

A
  • 2 monomers that form a dimer
  • each monomer has 7 catalytic activities and acyl carrier proteins
  • the acyl carrier protein contains a phosphopantetheine group that binds with the other monomers cysteinyl sulfhydryl group. (thioester bond)
17
Q

What are the four stages of the FA synthesis process?

A
  • condensation: loss of ACP, and CO2
  • reduction: NADPH—> NADP+
  • dehydration: loss of water
  • reduction: NADPH—> NADP+
18
Q

What three enzymes are used in the desaturation of FA in order, and what is the final product?

A
  • NADH cytochrome b5 reductase
  • cytochrome b5
  • stearoyl CoA desaturase: produces oleoyl CoA and water
19
Q

What are the two main components required for TAG synthesis?

A

TAGs can form from glycerol or glucose. The main intermediate is G-3-P

20
Q

What are the steps to forming TAGs?

A

G-3-P converts to phosphatidic acid; converts to diacylglycerol; converts to TAG and combine with apoproteins to move to the liver as very low density lipoproteins

21
Q

What is needed to form eicosanoids?

A

phospholipids and diacylglycerols

22
Q

What are the types of eicosanoids that exist?

A
  • leukotriene (B4)
  • prostacyclin (PGI2): vasodilator
  • thromboxane A2: vasoconstrictor
  • prostaglandin (E2)
23
Q

Lipoxygenases form what type of eicosanoids?

A

-leukotrienes

24
Q

Prostaglandin synthase forms what type of eicosanoids?

A
  • prostaglandin
  • prostacyclin
  • thromboxane
25
Q

What are the products of phosphatidic acid in the mechanism 1?

A
  • phosphatidylcholine

- phosphatidylethanolamine

26
Q

What products form from mechanism 2 from phosphatidic aicd?

A
  • phosphatidylinositol

- cardiolipin: major component of mito. matrix

27
Q

What is the main difference between mechanism 1 and 2 in the phospholipid synthesis?

A

the main difference is where the CDP head group attaches to the diacylglycerol.

  • mech 1: adds CDP-head group in one step
  • mech 2: adds CDP and then adds the head group.
28
Q

What component is the primary “hub” for forming phosphatidylserine/choline?

A
  • PE is swapped to PS

- PE if methylated forms PC

29
Q

Cholesterol is derived from what?

A

Acetyl CoA and Acetoacetyl CoA

30
Q

What is the rate limiting/control step of cholesterol production?

A
  • HMG CoA Reductase
  • -converts acetyl CoA to mevalonate.
  • -produces 2 NADP+ and CoA
31
Q

Where do statins work primarily to reduce the level of cholesterol?

A

-at HMG CoA reductase, the rate limiting step

32
Q

What happens during fasting after mevalonate is formed? There is a second compound produced, what is it and what will it do?

A
  • acetyl CoA and acetoacetate

- -instarvation acetyl CoA forms ketone bodies

33
Q

Stage 2 of cholesterol synthesis is how many steps, and how many C’s from start to finish?

A
  • occurs in three reactions and start with 5–>10–>15–>20 C’s
  • squalene is able to begin the ring cyclization of cholesterol.
34
Q

What is the name of the enzyme that helps stabilize the structure for ring formation?

A

-oxidosqualene cyclase, maintains the ring structure of the intermediates until stabile cholesterol is formed

35
Q

The accumulation of cholesterol is what?

A

LDL that allows release into blood stream and delivers cholesterol to the liver and peripheral tissue

36
Q

HDL is able to transfer APoE and APoCII to what molecules?

A
  • chylomicrons
  • VLDL
  • IDL
  • LDL
37
Q

If a person has a cholesterol ester transfer protein mutation or deficiency what is the ultimate problem?

A

-TAG and phospholipids are not able to transfer from LDL, VLDL, IDL to HDL.