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T2: Theme 3: CVS > Lecture 15: Lipid metabolism > Flashcards

Lecture 15: Lipid metabolism Flashcards

1
Q

What are the biological functions of lipids?

A

Cell membranes
Energy storage
Steroid hormones
Metabolism

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2
Q

What make up a triglyceride?

A

Glycerol + 3 FAs

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3
Q

What fats are for storage?

A

TGs

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4
Q

What fats are used for membranes?

A

Phospholipids - glycerophospholipids and sphingolipids

Glycolipids - sphingolipids

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5
Q

What make up a glycerophospholipid?

A

Glycerol + 2 FA + phosphate + alcohol

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6
Q

What make up a sphingolipid (phospholipid)?

A

Sphingosine + FA + phosphate + choline

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7
Q

What make up a sphingolipid (glycolipid)?

A

Sphingosine + FA + mono or oligosaccharide

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8
Q

What is beta-oxidation?

A

Oxidation of long chain fatty acids to 2 carbon fragments in the form of acetyl-CoA

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9
Q

Where does b-oxidation occur?

A

In the mitochondria and in peroxisome

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10
Q

How are fatty acids moved into the mitochondrial matrix?

A

Carnitine carrier protein - the acyl is transferred from the coenzyme-A to carnitine, this is transferred across the membrane into the matrix where it then detaches from the carnitine and bind to CoA present in the matrix.

Each transfer of FA requires carnitine palitoyl transferase (1 or 2)

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11
Q

Where is carnitine palmitoyl transferase 1 found?

A

Cytosol

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12
Q

Where is carnitine palmitoyl transferase 2 found?

A

Mitochondrial matrix

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13
Q

What is the rate limiting step of b-oxidation?

A

Transfer of acyl groups across the mitochondrial matrix

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14
Q

What are the three stages of b-oxidation?

A

1: FA activated by attachment of Coenzyme A
2: transfer of acyl across mitochondrial membrane
3: progressive oxidation FA by removal of 2 carbon units to form acetyl-coA (which enters citric acid cycle)

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15
Q

What three molecules are formed during each cycle of b-oxidation?

A

1 acetyl coA
1 FADH2
1 NADH

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16
Q

What is the first reaction for the removal of acetyl coA from fatty acyl-coA?

A

Fatty acyl CoA to trans-enoyl CoA

Enzyme = acyl-coA dehydrogenase

17
Q

A mutation in which enzyme will cause SIDS?

A

Acyl-coA dehydrogenase

18
Q

Where does fatty acid synthesis occur?

A

In the cytosol (mainly in the liver and adipocytes)

19
Q

How does acetyl-coA get out of the mitochondria?

A

By the citrate malate cycle

20
Q

Describe the citrate malate cycle.

A

OAA + acetyl-coA –> citrate

Citrate leaves the cell by tricarboxylate transporter

In the cytosol citrate is converted back to OAA and acetyl-coA

Acetyl-coA used for FA synthesis

OAA converted to malate then pyruvate and pyruvate is shuttled back into the mitochondria by the pyruvate transported

21
Q

What is the rate limiting step of FA synthesis?

A

Carboxylation of acetyl-CoA to make malonyl-CoA

Catalysed by acetyl CoA carboxylase

22
Q

In FA synthesis, what is acetyl CoA first converted into?

A

Malonyl-CoA

23
Q

How is FA synthase regulated?

A

Malonyl-CoA and acetyl-CoA both bing to FA synthase

24
Q

What type of reaction adds further C2 units in FA synthesis?

A

Condensation reactions

25
Q

How is acetyl-CoA carboxylase regulated?

A

Subject to phosphorylation under the control of glucagon (inactivates) and insulin (activates)

26
Q

What enzyme catalyses the formation of cholesterol esters?

A

Acyl-CoA Cholesterol Acyltransferase (ACAT)

27
Q

How is cholesterol stored?

A

In the form of cholesterol esters

28
Q

What are bile acids used for?

A

Lipid digestion
Lipid absorption
Cholesterol excretion

29
Q

What is the rate limiting step of cholesterol synthesis?

A

Conversion of HMG-CoA to Mevalonate

Enzyme: HMG-CoA Reductase

30
Q

Where is the major site of cholesterol synthesis?

A

Liver

some in intestine and adrenal cortex

31
Q

What is the target for statins?

A

HMG-CoA reductase

32
Q

How is HMG-CoA reductase regulated?

A

Both cholesterol and mevalonate are feedback inhibitors

33
Q

What do chylomicrons transport?

A

Dietary TGs to muscle and adipose tissue and dietary cholesterol to the liver

34
Q

What do VLDLs transport?

A

Endogenous TGs and cholesterol

35
Q

What do LDLs transport?

A

Cholesterol from the liver to tissues

36
Q

What do HDLs transport?

A

Cholesterol from tissues to liver

37
Q

What are the two stages of dietary TG digestion?

A

1: emulsification by bile acids
2: hydrolysis by the enzyme pancreatic triacylglycerol lipase

38
Q

What is PCSK9?

A

Binds to LDL receptors and cause their degradation

39
Q

What is SREBP?

A

Increases expression of LDL receptors in response to low cholesterol

T2: Theme 3: CVS (18 decks)

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