Cell metabolism 2 (beta oxidation )

Question 1

What is the 1st step to do before beta oxidation can happen

Answer 1

Fatty acid needs to be converted into acyl CoA
Fatty acid in the presence of acyl CoA synthetase is converted into Acyl CoA
ATP is converted into AMP

Question 2

How is Acyl CoA transported into the cytoplasm

Answer 2

via the carnitine shuttle

Question 3

Describe how the carnitine shuttle works

Answer 3

Carnitine reacts with Acyl CoA to produce acyl carnitine (in the presence of carnitine acyltransferase 1 - CAT 1)

It is transferred into the cytoplasm by translocase

acyl carnitine reacts with CoA to produce acyl CoA in the presence of CAT 2

Question 4

What is primary carnitine deficiency

Answer 4

mutation in SLC22A5 that encodes a carnitine transporter which results in a reduced ability of the cell to take in carnitine

Question 5

What are the symptoms of primary carnitine deficiency and explain their pathophysiology

Answer 5

cardiomyopathies (as heart uses energy from fatty acids )
muscle weakness (as adipose tissues are a storage site of fats)
hypoglycemia (as glucose is used as an alternate energy source )

Question 6

How common is primary carnitine deficiency in the USA

Answer 6

1 in 100,000 live births in the USA per year

Question 7

How common is primary carnitine deficiency in Japan and the Faroe Islands

Answer 7

1 in 40,000 in Japan

1 in 500 in the Faroe Islands

Question 8

How is primary carnitine deficiency treated

Answer 8

carnitine supplements

Question 9

Describe the stages of beta oxidation and the enzymes used at each stage

Answer 9

stage 1
Enzyme: Acyl CoA dehydrogenase
FAD is reduced to FADH2
Acyl CoA is oxidised

Stage 2:
hydration
enzyme: enoyl CoA hydratase

Stage 3:
NAD+ is reduced to NADH
product is oxidised
enzyme: beta hydroxyacyl -CoA dehydrogenase

stage 4:
enzyme: thiolase
acetyl CoA is formed and the acyl CoA chain is reduced by 2 carbon atoms

Question 10

For palmitoyl CoA ( a 16 chain acyl CoA) how many beta oxidation cycles will it go through

Answer 10

7 beta oxidation cycles

Question 11

For palmitoyl CoA ( a 16 chain acyl CoA) how many acetyl CoA molecules would it produce

Answer 11

8 Acetyl CoA molecules

Question 12

For palmitoyl CoA ( a 16 chain acyl CoA) how many FADH2 and NADH molecules would it produce

Answer 12

7 of each

Question 13

what does the phrase ‘fat burns in the flame of carbohydrate’ mean

Answer 13

oxalo-acetate must combine with Acetyl- CoA in the Krebs cycle
so if there isnt enough oxaloacetate (eg in starvation) ketone bodies are formed

Question 14

What are the products of ketone body production

Answer 14

acetone
acetoacetate
D 3 hydroxybutyrate

Question 15

How are ketone bodies produced

Answer 15

2 Acetyl CoA forms acetoacetyl CoA
Acetoacetyl CoA then forms 3 Hydroxy 3methyl glutaryl CoA
which forms acetoacetate
acetoacetone can form i) acetone ii) 3 hydroxybutyrate