Fatty Acids/ Ketones

Question 1

Give 4 examples of fatty acids

Answer 1

Linoleic acid - 18C
Oleic acid - 18C
Palmitic acid - 16C
Arachidonic- 20C

Question 2

Where are fatty acids activated before they’re oxidised

Answer 2

Activated in cytoplasm

Oxidised in mitochondria

Question 3

How does transport differ if the acyl CoA is <12C vs >14C

Answer 3

<12C - can diffuse through mitochondrial membrane

> 14C - taken through mitochondrial membrane using the carnitine shuttle

Question 4

How is acyl-CoA formed from a fatty acid

Answer 4

FA —> acyl adenylate —> acyl-CoA

First step - ATP broken down
2nd step - uses CoA

Question 5

What enzyme catalyses the conversion of acyl adenylate to acyl-CoA

Answer 5

acyl-CoA synthetase

Question 6

Briefly describe the steps of the carnitine shuttle

Answer 6

Acyl CoA —> acyl carnitine catalysed by CAT 1 located on outer mitochondrial membrane

Acyl CoA moves into the intermembrane space

Acyl carnitine reformed to acyl CoA by CAT 2 located on interior side of outer membrane

Question 7

What does CAT 1 stand for

Answer 7

Carnitine acyltransferase 1 & 2

Question 8

What are the products of one round of beta oxidation

Answer 8

1 NADH
1 FADH2
1 acetyl CoA

Question 9

Give the 4 steps of beta oxidation

Answer 9

1. Acyl CoA is oxidised by FAD+ to form FADH2 and a new double bond molecule
   This is catalysed by acyl-Co A dehydrogenase
2. This new molecule undergoes hydration to form a new hydroxyl group
   Catalysed by Enol-CoA hydrate
3. This hydroxyl group is oxidised to a new carbonyl group by NAD+ so NADH is formed
   Catalysed by hydroxyacyl CoA dehydrogenase
4. This compound then undergoes thiolysis in the presence of thiolase to form acetyl-CoA

Question 10

Give 3 ketone bodies

Answer 10

Acetone
Acetoacetate
Beta-hydroxybutyrate

Question 11

When is ketogenesis increased

Answer 11

During high rates of FA oxidation, large amounts of acetyl-CoA are generated
This exceed the capacity of Krebs cycle

Question 12

How many acetyl-CoA’s are converted to acetoacetyl-CoA and which enzyme catalyses this

Answer 12

2

Thiolase

Question 13

Which type of muscle utilise ketone bodies for energy

Answer 13

Heart and skeletal muscle

Question 14

Give 4 factors the affect ketogenesis

Answer 14

1. Release of free FA
2. Low [G-3-P] in liver results in increased ketogenesis
3. High ATP demand means acetyl-CoA is more likely to be further oxidised by krebs cycle
4. Fat oxidation is dependent on glucagon (activation) and insulin (inhibition)