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ESA2 - Metabolism, Endocrinology and Haematology > Energy Production - Lipids > Flashcards

Energy Production - Lipids Flashcards

1
Q

Why do lipids release more energy than carbohydrates when oxidised?

A

They are more reduced than carbohydrates

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2
Q

What 3 classes of lipids are there?

A
  1. Fatty acid derivatives (eg triacylglycerols)
  2. Hydroxy-methyl-glutaric acid derivatives (eg ketone bodies)
  3. Vitamins (A D E and K)
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3
Q

What are some hydroxy-metyl-glutaric acid derivatives?

A

Ketone bodies (C4)
Cholesterol (C27)
Cholesterol esters
Bile acids and salts (C24)

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4
Q

What are some fatty acid derivatives?

A

Fatty acids, triacylglycerols, phospholipids and eicosanoids

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5
Q

In what form are triacylglycerols stored?

A

Anhydrous form (lipid droplets) as they are hydrophobic - so stored in adipose tissue

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6
Q

Where are fatty acids converted back to triglycerides?

A

GI Tract

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7
Q

What are chylomicrons?

A

Chylomicrons are lipoprotein particles that consist of triglycerides, phospholipids, cholesterol, and proteins. They transport dietary lipids from the intestines to other locations in the body.

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8
Q

What is meant by an unsaturated fatty acid?

A

Fatty acid with one or more double bonds

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9
Q

What is an example of an essential fatty acid?

A

Linolenic acid

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10
Q

Where does stage 2 of fatty acid metabolism occur?

A

Mitochondria

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11
Q

In fatty acid catabolism, how is the fatty acid activated?

A

By linking to coenzyme A outside the mitochondrion by the action of fatty acyl CoA synthase

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12
Q

How is the activated fatty acid transported across the inner mitochondrial membrane?

A

Using a carnitine shuttle

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13
Q

How are fatty acids catabolised?

A

FA cycles through sequence of oxidative reactions with 2 carbons removed each cycle

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14
Q

What is the carnitine shuttle inhibited by?

A

Malonyl~CoA

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15
Q

For a C6 fatty acid, how many moles of ATP are generated?

A

41

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16
Q

Where does b-oxidation of fatty acids not occur?

A

Brain, RBC and WBC

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17
Q

Where is glycerol metabolised?

A

Liver

18
Q

Which enzyme converts glycerol into glycerol phosphate?

A

Glycerol kinase

19
Q

What 3 ketone bodies are produced in the body?

A

Acetoacetate, acetone and b-hydroxybutyrate

20
Q

What is the normal plasma ketone body concentration?

A

< 1 mM

21
Q

What is the range of ketone body concentration in starvation (physiological ketosis)?

A

2-10 mM

22
Q

What can be the ketone body concentration in a patient with untreated type 1 diabetes?

A

> 10 mM (pathological ketosis)

- reduced insulin, reduced glucose uptake

23
Q

What are ketone bodies synthesised by?

A

Liver mitochondria

24
Q

What do station drugs ultimately inhibit?

A

Production of cholesterol

Inhibits HMG-CoA Reductase

25
Q

What does CoA contain?

A

Vitamin B5

26
Q

When the insulin/glucagon ratio is high, what is the state of lyase and reductase?

A

Lyase is inhibited, reductase activated -> cholesterol synthesis

27
Q

When the insulin/glucagon ratio is low, what is the state of lyase and reducatase?

A

Lyase activated, reductase inhibited -> ketone body synthesis

28
Q

True or False:

By using alternative substrate eg ketone bodies for muscles, glucose is conserved for the brain

A

True

29
Q

Are ketone bodies hydrophobic or hydrophilic?

A

Hydrophilic

30
Q

What can be made from HMG-CoA?

A

Mevalonate which can go on to make cholesterol

Or ketone bodies (acetoacetate, actone, b-hydroxybutyrate)

31
Q

What is HMG and what can it go on to synthesise?

A

Hydroxymethyl glutaric acid (3 acetyl coAs condensed together)

Ketone bodies, cholesterol (and therefore steroid hormones)

32
Q

What can fatty acids go on to synthesise?

A

Triaceylglycerols and phospholipids

33
Q

What are the 3 pathways that acetyl-CoA can go on to?

A

Fatty acids, TCA cycle, HMG

34
Q

What is the main convergence point for catabolic pathways?

A

Acetyl-CoA

35
Q

What is the CH3CO group linked to coenzyme A by?

A

Via S-atom - high energy of hydrolysis

36
Q

What can glycerol phosphate go on to do?

A

Triacylglycerol synthesis or DHAP in glycolysis

37
Q

What are the products of b-oxidation of fatty acid catabolism?

A

Acetyl-CoA, AMP, 2Pi, FADH2, NADH and H+

Acetyl CoA goes to TCA cycle
FADH2, NADH + H+ goes to ETC

38
Q

True or False:

B-oxidation stops in the absence of O2

A

True

39
Q

True or False:

No ATP is synthesised in b-oxidation

A

True

40
Q

Explain how acetyl-CoA can be diverted from the TCA cycle to synthesise ketone bodies

A

An increase in b-oxidation of fatty acids leads to increased production of NADH, meaning a low NAD+ substrate

NADH builds up and inhibits the actions of isocitrate dehydrogenase and a-ketoglutarate dehydrogenase in TCA cycle (product inhibition)

TCA therefore stops and acetyl-coA is diverted away to synthesise ketone bodies

ESA2 - Metabolism, Endocrinology and Haematology (19 decks)

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