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biochemistry > Fat and lipid metabolism > Flashcards

Fat and lipid metabolism Flashcards

1
Q

Where are triglycerides stored?

A

Adipocytes

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2
Q

Which components does a triglyceride consist of?

A
  • Glycerol
  • Three fatty acids
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3
Q

Which enzyme breaks triglycerides down?

A

Lipase

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4
Q

How are triglycerades taken up by cells?

A

As fatty acids

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5
Q

Which products are released into the small intestine to produce fatty acids and 2-monoacylglycerol?

A
  • Bile salts
  • HCO3-
  • Lipase
  • Colipase

Bile secreted in the ileum entering the portal vein, HCO3- increases pH

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6
Q

In which cells are the fatty acids and 2-monocylglycerols taken up?

A

Enterocytes

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7
Q

What are fatty acids and 2-monocylglycerides made into in the enterocytes?

A

Chylomicrons

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8
Q

What are chylomicrons?

A

Core of fat surrounded by phospholipids

This makes them water soluble so that fat can be transported

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9
Q

What do bile salts do?

A

Emulsify fat droplets into micelles

These are accesible to enzymes

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10
Q

What happens when triacyl lipase is exposed to water?

A

The ‘lid’ of the enzyme stays closed

It can only bind with fat

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11
Q

How are fatty acids activated for resynthesis of triacylglycerols?

A
  1. FA forms FA-ATP
  2. FA-ATP + CoA SH forms FA CoA

ATP in FA ATP is released as AMP

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12
Q

What does FA-CoA do?

A

It adds fatty acids to mono- and diacylglycerol molecules.

CoA released as CoA SH

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13
Q

Function of lipoproteins?

A

Transport fats

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14
Q

What perentage from chylomicrons are triglycerides?

A

85%

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15
Q

How do chylomicrons bypass the liver?

A

Through the lymph into the blood

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16
Q

Where do fatty acids get stored?

A
  • Muscle
  • Adipose tissue
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17
Q

Where do glycerol and chylomicron remnants go to?

A

Liver

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18
Q

What happens if there is a surplus of carbohydrates and proteins?

A

Production fat

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19
Q

How are free fatty acids transported?

FA’s not water soluble

A

As FFA-albumin complex

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20
Q

How can fats be used?

A
  • Storage as triglycerides
  • Beta-oxidation
  • Synthesis of membrane lipids
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21
Q

In which mitochondrial membrane is Acetyl CoA produced from Fatty acyl CoA?

A

Inner mitochondrial membrane

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22
Q

Where are long-chain fatty acid-albumin complexes processed?

A

Mitochondria

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23
Q

Which enzyme activates fatty acids for transportation?

A

Long chain acyl CoA synthetase

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24
Q

How is Fatty Acyl CoA imported into the mitochondria?

A

By replacing CoA by carnitin

By acylcarnitine translocase

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25
Q

What happens to acylcarnitine in the inner membrane?

A
  1. Converted into Acyl CoA
  2. Carnitine back to the cytoplasm
  3. Acyl CoA used in beta oxidation
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26
Q

Where is acylcarnitine produced?

A

Outer membrane

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27
Q

What is beta-oxidation

A

Degradation of fatty acids to 2-carbon acetyl CoA

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28
Q

What molecules are produced from palmitate during beta-oxidation?

C16

A
  • 8x acetyl CoA
  • 7x FAD (2H)
  • 7x NADH
29
Q

Where can very long-chain fatty acids be degraded?

A

Peroxisomes

30
Q

What happens during degradation of very long-chain fatty acids in peroxisomes?

A
  • Production of reactive oxygen species

Which can be neutralized by catalase

31
Q

What is the difference between the process of saturated and unsaturated fats?

A

Unsaturated fats need more steps to be processed

32
Q

Which products are produced from odd-chain fatty acids such as Margaric acid?

C17

A
  • 7x Acetyl CoA
  • 1x Propionyl CoA
  • 7x FAD (2H)
  • 7x NADH
33
Q

What is propionyl CoA converted into?

A

Succinyl CoA (TCA cycle)

34
Q

Which amino acids are also converted into propionyl CoA?

A
  • Valine
  • Isoleucine
35
Q

Which groups of compounds produce acetyl CoA?

A
  • Carbohydrates
  • Fatty acids
  • Amino acids
36
Q

Where are ketone bodies produced?

A

Liver

37
Q

How do ketone bodies produce Acetyl CoA?

A
  1. D-b-hydroxybuterate to acetoacetate by dehydrogenase
  2. Acetoacetate to acetoacetyl CoA by CoA transferase from succinyl CoA
  3. From acetoacetyl CoA to 2 acetyl CoA by thiolase
38
Q

How are ketone bodies produced from 2 acetyl CoA?

A
  1. To acetoacetyl CoA by thiolase
  2. To HMG CoA by HMG CoA synthase
  3. To acetoacetate by HMG CoA lyase
  4. To acetone and D-b-hydroxybutyrate by D-b-hydroxybutyrate dehydrogenase
39
Q

What is the product of fatty acid synthesis?

A

Palmitate

40
Q

What is the product of fatty acid degradation?

A

Acetyl CoA

41
Q

Where does fatty acid synthesis take place?

A

Cytosol

degradation in the mitochondria

42
Q

What compounds are carriers of acyl-acetyl groups between mitochondria and cytosol?

A
  • To mitochondria: carnitine
  • To cytosol: citrate
43
Q

Which building block is used during fatty acid synthesis?

In cytoplasm

A

Malonyl CoA

44
Q

How is malonyl CoA produced?

A

From Acetyl CoA by Acetyl CoA carboxylase

45
Q

Can Acetyl CoA to malonyl CoA be reversed?

A

No

46
Q

What is fatty acid synthase composed of?

A

Two identical 272 kDa polypeptides forming a multienzymatic structure

47
Q

Citrate (for crossing mitochondrial membrane) is composed of which molecules?

A
  • oxaloacetate
  • Acetyl CoA
48
Q

What is the function of malonyl CoA?

A

To extend the carbon chain with fatty acid synthase

49
Q

What happens in the ‘foot and head’ of FA synthase?

A
  1. Foot: Condensation and transfer
  2. Head: Modification

Condensation: 2 molecules form one, usually losing a small molecule

STUDY THIS LATER!!!

50
Q

What compound does the synthesis of FA need in the synthase complex?

A

NADPH

Therefore, when there is enough energy, NADPH also stimulates synthesis

51
Q

What happens to FA’s in the endoplasmatic reticulum?

A

Palmitate is converted into longer/unsaturated fatty acids

52
Q

Which fatty acids are essential?

A

Omega 3 and 6

53
Q

Which compounds inhibit the TCA cycle?

A
  • Citrate
  • Acetyl CoA inhibits pyruvate dehydrogenase
  • NADH
54
Q

What happens when there is an excess of acetyl CoA and too much energy?

A

Pyruvate is converted into oxaloacetate by pyruvate carboxylase

55
Q

What is the shuttle concept in the TCA cycle?

A

Citrate is transported out of the mitochondria and converted into pyruvate again, which can go into fatty acid synthesis.
Citrate transport is coupled to NADH to NADPH

Because there is alot of NADH produced, this cylce is facilitated

56
Q

How is malonyl CoA production controlled?

A
  1. By AMP and citrate
  2. By insulin and glucagon
57
Q

How do citrate and AMP activate inactive carboxylase?

A
  1. Phosphate group binds to active carboxylase making it inactive
  2. Citrate binds to inactive carboxylase making it partly active again
58
Q

How does glucagon influence carboxylase?

A

Activates AMP activated protein kinase to make carboxylase inactive

No fatty acids can be produced

59
Q

How does insulin influence carboxylase?

A

Insulina activates protein phosphatase 2A to remove the phophate group from inactive carboxylase making carboxylase active

Fatty acid synthesis activated

60
Q

When is carboxylase a polymer?

A

When it is (partially) activated

61
Q

How does palmitate influence fatty acid synthesis?

A

Conversion to palmitoyl CoA inhibits acetyl CoA carboxylase

62
Q

How is a futile fatty acid cycle prevented?

Futile=without purpose

A
  • NADH and FAD (2H) inhibit conversion of fatty acid cartinine to acetyl CoA
  • Malonyl CoA inhibits conversion fatty acyl CoA to fatty acyl cartinine
  • Insulin activates carboxylase, increasing malonyl CoA

Look at slide 64

63
Q

How does malonyl CoA inhibit beta oxidation?

A

Inhibits entry of free fatty acid into mitochondria

64
Q

Where is NADPH mainly produced?

A

From the pentose phosphate pathway

The first conversions from glucose in the cytosol

65
Q

How much glucose is converted in the pentose phosphate pathway?

A

30%

66
Q

How are fatty acids transported to other tissues?

A

As triglycerides

67
Q

How does insulin influence the concentration of free fatty acids in the blood?

A

Lipoprotein lipase is upregulated and liberates FFA from triglycerides for uptake

68
Q

Why does adipose tissue need glucose to produce triglycerides?

A

Because the cells lack the enzyme glycerol kinase

biochemistry (13 decks)

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