3. Lipids & Ketone bodies Flashcards

1
Q

Are lipids more or less reduced than carbohydrates?

A

More reduced - produce more energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the 3 classes of lipids?

A
  1. FA derivatives - FA, TAG, phospholipids
  2. HMG derivatives - cholesterol, cholesterol esters, ketone bodies
  3. Vitamines - A,D,E, K
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are TAGs stored?

A

Anhydrous form as lipid droplets in adipose tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What triggers FA release from adipose tissue?

A

Low plasma [glucose] means that less glycerol-1-phosphate is produced in adipose cells, causing FA to be released into the circulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 3 steps in FA metabolism in target tissues?

A
  1. Activation in cytoplasm
  2. Carnitine shuttle transport into IMM
  3. Beta-oxidation - C2 removed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What enzyme is responsible for FA oxidation?

A

Fatty acyl CoA synthase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What controls the rate of FA oxidation?

A

Carnitine shuttle, inhibited by Malonyl CoA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In beta oxidation, what are the intermediates linked to?

A

CoA - leave as Acetyl CoA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the fate of Acetyl CoA from beta oxidation?

A

TCA cycle to provide energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which tissues can beta oxidation occur in?

A

Most tissues with mitochronidria - Not brain, RBC or WBC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Can beta oxidation occur without O2?

A

No - needs NAD+ and FAD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the fate of glycerol released from adipose tissue?

A

transported back to liver, into glycerol phosphate which can enter glycolysis as DHAP or TAG synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which enzyme converts glycerol to glycerol-1P?

A

Glycerol kinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What 3 ketone bodies are produced in the body?

A
  1. Acetone
  2. Acetoacetate
  3. beta-hydroxybutyrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where are ketone bodies produced?

A

Acetone and b-hydroxybutyrate in mitochondia in the liver.

Acetoacetate is formed from decarboxylation of acetone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Do ketone bodies need protein transport in the blood?

A

No, they are water soluble.

17
Q

What condition may present with ketoacidosis?

A

Unmanaged type 1 diabetes

18
Q

How does the liver know when to make ketone bodies from Acetyl CoA and not cholesterol?

A

When [glucose] is low, FA will be oxidised which produces NADH.
NADH inhibits the rate limiting enzymes of the TCA cycle.

19
Q

What enzyme catalyses the conversion of HMG-CoA to acetoacetate?

A

Lyase

20
Q

How does the insulin:glucagon ratio control ketone body synthesis?

A
Insulin = fed state. Inhibits Lyase and stimulates HMG CoA reductase.
Glucagon = starvation. Stimulates lyase and inhibits HMG CoA reductase.
21
Q

After two additional reactions, the glycerol released upon the hydrolysis of triacylglycerol can enter which pathway?

A

Glycolysis.
After phosphorylation to glycerol phosphate and conversion to dihydroxyacetone phosphate, glycerol can enter glycolysis. It can also a precursor for gluconeogenesis by these same reactions.

22
Q

Why are ketone bodies a useful fuel source?

A

They can be used by all tissues containing mitochondria including the central nervous system

23
Q

Which 2 pathways can tissues obtain cholesterol if they need it?

A
  1. Direct synthesis of cholesterol from acetyl CoA within tissues
  2. Receptor mediated endocytosis of LDL particles.
24
Q

What happens in paracetamol overdose?

A

Normal metabolic pathway is saturated, alternative pathway producing NAPQI is used. NAPGI has a direct toxic effect on metabolites.
Glutathione conjugated to NAPQI, depleting liver of the important anti-oxidant.