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Biochem 2 > Lecture 13 - Lipid Synthesis > Flashcards

Lecture 13 - Lipid Synthesis Flashcards

1
Q

What breaks down triglycerides to fatty acids?

A

Lipases

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2
Q

What breaks down fatty acids to acetyl CoA?

A

Beta-oxidation

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3
Q

What breaks down acetyl CoA to CO2?

A

TCA cycle

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4
Q

____ are more efficient energy storage than ______

A
  • Fatty acids

- Carbohydrates

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5
Q

What is the precursor of fatty acid biosynthesis?

A

Acetate

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6
Q

Do beta-oxidation and fatty acid synthesis use the same enzymes?

A

Nope

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7
Q

Where does fatty acid synthesis occur?

A

Cytoplasm

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8
Q

Where does beta-oxidation occur?

A

Mitochondria

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9
Q

What is required as an activator for fatty acid synthesis?

A

Citrate

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10
Q

What is required but not incorporated in fatty acid synthesis?

A

CO2

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11
Q

What is the principle enzyme of fatty acid synthesis?

A

Fatty acid synthase

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12
Q

What is fatty acid synthase like in eukaryotes?

A

One large protein, with several activities

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13
Q

What is fatty acid synthase like in prokaryotes?

A

Complex of several proteins, each with a different activity

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14
Q

What occurs in the preparatory phase of fatty acid synthesis?

A

Acetyl CoA is converted to malonyl CoA

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15
Q

What enzyme is used in the preparatory phase of fatty acid synthesis?

A

Acetyl CoA carboxylase

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16
Q

What cofactor is needed in the preparatory phase of fatty acid synthesis?

A
  • CO2 in
  • ATP -> ADP + Pi
  • Biotin
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17
Q

Which step is the rate limiting step of fatty acid synthesis?

A

The preparatory phase/step

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18
Q

What controls the slowest step of fatty acid synthesis and what is it needed for?

A
  • Citrate

- Required for oligomerization of the enzyme

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19
Q

Why is biotin needed for the preparatory phase of fatty acid synthesis?

A

CO2 carrier

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20
Q

What are the 2 activities that occur in acetyl CoA carboxylase and what does each do?

A

1) Biotin carboxylase - attaches CO2 to biotin

2) Transcarboxylase - transfers CO2 from biotin to acetyl CoA, making malonyl CoA

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21
Q

What is the active portion of the acyl-carrier protein and what does it form?

A

-SH forms thiol esters with fatty acid molecules

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22
Q

What type of chain does acyl-carrier protein have?

A

4-phosphopantetheine chain

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23
Q

What does the 4-phosphopantetheine chain do?

A

“Carries” the growing fatty acid chain from enzyme to enzyme (bacteria) or active site to active site (eukaryotes)

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24
Q

What are the 2 sources of NADPH?

A

1) From pentose phosphate pathway in liver cells

2) From malic enzyme in fat cells

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25
Q

What are the sources of acetyl CoA?

A

Ethanol, pyruvate, amino acids, acetate, and citrate

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26
Q

What enzyme and cofactor are needed to generate acetyl CoA from citrate?

A
  • ATP-citrate lyase

- ATP -> ADP + Pi

27
Q

Where does production of acetyl CoA from citrate occur?

A

Cytoplasm

28
Q

Where does production of citrate from acetyl CoA and oxaloacetate occur?

A

Mitochondria

29
Q

What happens to excess acetyl CoA in the mitochondria?

A
  • Converted to citrate in mitochondria
  • Transported to cytoplasm
  • Shunted to fatty acid synthesis
  • Excess oxaloacetate is converted to malate, and then pyruvate can go back into mitochondria to pick up more acetyl CoA
30
Q

At which carbons can unsaturations be introduced?

A

C4, C5, C6, and C9

31
Q

What enzyme and cofactor are needed to introduce an unsaturation?

A
  • Fatty acyl-CoA monoxygenase

- O2 -> 2 H2O and NADH + H+ -> NAD+

32
Q

How is fatty acid synthesis controlled?

A

1) Enzyme activity
2) Transcription
3) Hormones

33
Q

What is the central role of citrate?

A

To control energy metabolism

34
Q

What does citrate activate?

A

Gluconeogenesis, for energy storage

35
Q

What does citrate inhibit?

A

Energy release

36
Q

What does citrate act as during energy rich conditions?

A

A source of acetyl CoA for additional lipid synthesis

37
Q

What does protein kinase activate?

A

Pancreatic lipases and beta-oxidation

38
Q

What does protein kinase inactivate?

A

Lipid synthesis

39
Q

What does insulin activate during high glucose conditions?

A

Acetyl CoA synthesis, as a means of storing energy in the form of fat

40
Q

Energy poor conditions induce transfer of metabolites to _______ for _____

A
  • Mitochondria

- Energy production

41
Q

Energy rich conditions induce transfer of metabolites to ______ for

A
  • Cytoplasm

- Fatty acid synthesis (energy storage)

42
Q

Are fatty acids normally found as free entities?

A

Nope

43
Q

How do fatty acids primarily exist?

A

In complex lipids

44
Q

What are the precursors for steroid hormones?

A

Cholesterol

45
Q

Are cholesterol, phospholipids, and triacylglycerols soluble or insoluble and what does this mean?

A
  • Insoluble

- Must be transported by protein carriers in blood

46
Q

What are the 4 types of lipoproteins?

A

1) HDL
2) LDL
3) VLDL
4) Chylomicrons

47
Q

Which type of lipoprotein has the highest amount of cholesterol?

A

Chylomicrons

48
Q

What is the function of HDL’s?

A

Return cholesterol to the liver

49
Q

Which type of lipoprotein is the least dense?

A

Chylomicrons

50
Q

What is the function of chylomicrons?

A

Transport fatty acids to various tissues for fuel or storage

51
Q

Which lipoproteins have receptor mediated uptake?

A

Chylomicrons, VLDL, and LDL

52
Q

Where are VLDL’s made?

A

In liver when there is excess fatty acids

53
Q

What is the function of VLDL?

A

Transport triacylglycerols and cholesterol to muscle and adipose tissue

54
Q

What does a VLDL have to lose to become a LDL?

A

Triacylglycerol

55
Q

What is the function of LDL?

A

Transport cholesterol to hepatic tissues

56
Q

Which lipoprotein contains the highest amount of protein?

A

HDL

57
Q

What does HDL have that the other lipoproteins don’t and what does it do?

A

Has acyl transferases on surface to convert cholesterol to cholesterol esters

58
Q

What does a high LDL/HDL ratio indicate?

A

A need to reduce fat intake

59
Q

What does familial hypercholesterolemia lead to and why?

A
  • Increased LDL in blood -> plaque formation -> atherosclerosis
  • Express fewer LDL receptors
60
Q

Why is HDL considered “good cholesterol”?

A

Has acyl transferases which convert cholesterol to cholesterol esters, which transport cholesterol back to the liver for bile salts

61
Q

How can cholesterol biosynthesis be controlled?

A

Inhibition of HMG-CoA reductase

62
Q

What do resins do to bile acids?

A

Bind bile acids and remove them from metabolism, therefore causing more cholesterol to be converted to bile acids

63
Q

How can red wine decrease cholesterol?

A

Increases LDL receptor expression, suppresses secretion of apolipoproteins, and protects against oxidation of LDL

Biochem 2 (40 decks)

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