Energy Production - Lipids

Question 1

Why do lipids release more energy than carbohydrates when oxidised?

Answer 1

They are more reduced than carbohydrates

Question 2

What 3 classes of lipids are there?

Answer 2

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

Question 3

What are some hydroxy-metyl-glutaric acid derivatives?

Answer 3

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

Question 4

What are some fatty acid derivatives?

Answer 4

Fatty acids, triacylglycerols, phospholipids and eicosanoids

Question 5

In what form are triacylglycerols stored?

Answer 5

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

Question 6

Where are fatty acids converted back to triglycerides?

Answer 6

GI Tract

Question 7

What are chylomicrons?

Answer 7

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.

Question 8

What is meant by an unsaturated fatty acid?

Answer 8

Fatty acid with one or more double bonds

Question 9

What is an example of an essential fatty acid?

Answer 9

Linolenic acid

Question 10

Where does stage 2 of fatty acid metabolism occur?

Answer 10

Mitochondria

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Using a carnitine shuttle

Question 13

How are fatty acids catabolised?

Answer 13

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

Question 14

What is the carnitine shuttle inhibited by?

Answer 14

Malonyl~CoA

Question 15

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

Answer 15

41

Question 16

Where does b-oxidation of fatty acids not occur?

Answer 16

Brain, RBC and WBC

Question 17

Where is glycerol metabolised?

Answer 17

Liver

Question 18

Which enzyme converts glycerol into glycerol phosphate?

Answer 18

Glycerol kinase

Question 19

What 3 ketone bodies are produced in the body?

Answer 19

Acetoacetate, acetone and b-hydroxybutyrate

Question 20

What is the normal plasma ketone body concentration?

Answer 20

< 1 mM

Question 21

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

Answer 21

2-10 mM

Question 22

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

Answer 22

> 10 mM (pathological ketosis)

- reduced insulin, reduced glucose uptake

Question 23

What are ketone bodies synthesised by?

Answer 23

Liver mitochondria

Question 24

What do station drugs ultimately inhibit?

Answer 24

Production of cholesterol

Inhibits HMG-CoA Reductase

Question 25

What does CoA contain?

Answer 25

Vitamin B5

Question 26

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

Answer 26

Lyase is inhibited, reductase activated -> cholesterol synthesis

Question 27

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

Answer 27

Lyase activated, reductase inhibited -> ketone body synthesis

Question 28

True or False: By using alternative substrate eg ketone bodies for muscles, glucose is conserved for the brain

Answer 28

True

Question 29

Are ketone bodies hydrophobic or hydrophilic?

Answer 29

Hydrophilic

Question 30

What can be made from HMG-CoA?

Answer 30

Mevalonate which can go on to make cholesterol Or ketone bodies (acetoacetate, actone, b-hydroxybutyrate)

Question 31

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

Answer 31

Hydroxymethyl glutaric acid (3 acetyl coAs condensed together) Ketone bodies, cholesterol (and therefore steroid hormones)

Question 32

What can fatty acids go on to synthesise?

Answer 32

Triaceylglycerols and phospholipids

Question 33

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

Answer 33

Fatty acids, TCA cycle, HMG

Question 34

What is the main convergence point for catabolic pathways?

Answer 34

Acetyl-CoA

Question 35

What is the CH3CO group linked to coenzyme A by?

Answer 35

Via S-atom - high energy of hydrolysis

Question 36

What can glycerol phosphate go on to do?

Answer 36

Triacylglycerol synthesis or DHAP in glycolysis

Question 37

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

Answer 37

Acetyl-CoA, AMP, 2Pi, FADH2, NADH and H+ Acetyl CoA goes to TCA cycle FADH2, NADH + H+ goes to ETC

Question 38

True or False: B-oxidation stops in the absence of O2

Answer 38

True

Question 39

True or False: No ATP is synthesised in b-oxidation

Answer 39

True

Question 40

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

Answer 40

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