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Fundamentals of the Living Cell > Lipid synthesis and degradation (revised version) > Flashcards

Lipid synthesis and degradation (revised version) Flashcards

1
Q

What are triglycerides broken down into? [2 marks]

A
  • Fatty acids

- Glycerol

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2
Q

What can one of the components of triglycerides be fed into? [2 marks]

A

GLYCEROL

  • Glycolysis
  • Gluconeogenesis
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3
Q

Structure of fatty acids [3 marks]

A
  • Chains of methyl groups
  • Terminal carboxyl group
  • Cis configuration for double bonds
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4
Q

Where does fatty acid synthesis and degradation occur? [2 marks]

A
  • Synthesis occurs in the cytosol

- Degradation occurs in the mitochondria

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5
Q

What are the intermediates for fatty acid synthesis and degradation linked to? [2 marks]

A
  • Intermediates are linked to acyl carrier proteins (ACPs) in synthesis
  • Intermediates are linked to CoA in degradation
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6
Q

What are added and removed in fatty acid synthesis and degradation? [2 marks]

A
  • Sequential addition of 2 carbons in synthesis

- Sequential removal of 2 carbons in degradation

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7
Q

What is the reductant in fatty acid synthesis? [1 mark]

A

NADPH

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8
Q

What are the oxidants in fatty acid degradation? [2 marks]

A
  • FAD

- NAD

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9
Q

Where does NADPH for fatty acid synthesis come from? [2 marks]

A
  • 60% from pentose phosphate pathway

- 40% from acetyl CoA transfer

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10
Q

What is the preferred energy source for cardiac muscle? [1 mark]

A

Fats

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11
Q

What is involved in acetyl CoA transfer? [4 marks]

A
  • Acetyl CoA
  • Oxaloacetate
  • Citrate
  • Malate
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12
Q

What are the products of acetyl CoA transfer? [3 marks]

A
  • Pyruvate
  • CO2
  • NADPH
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13
Q

First step in fatty acid synthesis [3 marks]

A

Acetyl-CoA + ATP + HCO3- → malonyl-CoA + ADP + Pi

  • acetyl-CoA carboxylase
  • irreversible
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14
Q

What is involved in fatty acid elongation? [4 marks]

A
  • Acetyl CoA
  • Malonyl CoA
  • Acetoactyl-ACP
  • Butyryl-ACP
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15
Q

What enzyme is used in fatty acid synthesis and what is its structure? [4 marks]

A
  • Fatty acid synthase
  • Large and multi-enzyme
  • Lots of active sites
  • Dimer (makes synthesis more efficient)
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16
Q

What is the first step of fatty acid synthesis activated by? [1 mark]

A

Citrate (via positive feed back)

17
Q

What is the first step of fatty acid synthesis inhibited by?

A

Palmitic acid (via negative feed back)

18
Q

Where is cholesterol synthesised? [1 mark]

A

Endoplasmic reticulum

19
Q

What is the first step of cholesterol synthesis?

A

Activation of acetate

20
Q

What is the regulatory step of cholesterol synthesis? [1 mark]

A

HMGCoA → mevalonate

21
Q

What enzyme does cholesterol inhibit? [3 marks]

A
  • HMGCoA reductase
  • Involved in cholesterol synthesis
  • Target for statins
22
Q

Does cholesterol provide energy? [1 mark]

A

NO

23
Q

Where does fatty acid mobilisation occur and how is it mediated? [2 marks]

A
  • Happens in the adipocyte

- cAMP mediated (beta 3 adrenoceptor)

24
Q

What enzyme does protein kinase activate in fatty acd mobilisation and what does this enzyme do? [2 marks]

A
  • Triacylglycerol lipase

- Breaks down triglycerides into glycerol and free fatty acids

25
Q

Where does fatty acid activation (for degradation) occur? [1 mark]

A

In the liver cytosol

26
Q

What is involved in fatty acid activation (for degradation)? [3 marks]

A
  • Acyl CoA
  • Carnitine
  • Acyl carnitine
27
Q

What inhibits transport of acetyl CoA from cytosol to matrix? [1 mark]

A

Malonyl-CoA (made in fatty acid synthesis)

28
Q

Where does fatty acid degradation/β-oxidation occur? [1 mark]

A

In the liver mitochondria

29
Q

What is made form the removal of 2 carbon atoms in acyl-CoA in degradation? [3 marks]

A
  • FADH2
  • NADH
  • acetyl CoA
30
Q

In what conditions does acetyl-CoA enter the citric acid cycle?

A
  • Under glycolysis only

- Only in non hepatic cells

31
Q

What can acetyl-CoA form in hepatic cells? [1 mark]

A

Ketone bodies (then enter bloodstream)

32
Q

How many ATP molecules are ade from the oxidation of palmitate? [1 mark]

A

106

33
Q

What happens if the chain length of the fatty acid is odd? [2 marks]

A
  • Propionyl-CoA is made

- Double bonds removed by isomerase

34
Q

Which enzymes remove even numbered double bonds? [2 marks]

A
  • Reductase

- Isomerase

35
Q

What enzyme is inhibited by a low insulin/glucagon ratio? [1 mark]

A

Acetyl-CoA carboxylase

36
Q

Ketogenesis process [4 marks]

A

Acetyl-CoA → acetoacetyl-CoA → HMG-CoA → acetoacetate

37
Q

Which organs are ketone bodies a major energy source? [2 marks]

A
  • Cardiac muscle

- Renal cortex

38
Q

What is insulin’s negative effects on fat metabolism? [2 marks]

A
  • Negative effect on breakdown

- Negative effect on β-oxidation

39
Q

What is insulin’s positive effect on fat metabolism? [1 mark]

A

Fatty acid synthesis

Fundamentals of the Living Cell (35 decks)

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