Lipids 2

Question 1

What process does the body utilise to breakdown fatty acids?

Answer 1

beta oxidation

Question 2

Where does beta oxidation occur?

Answer 2

mitochondria

Question 3

What does beta oxidation produce as products?

Answer 3

acetyl-CoA which can enter the citric acid cycle
NADH and FADH2 which are used in terminal respiration
ketone bodies

Question 4

How are free fatty acids transported in the blood?

Answer 4

in complex with albumin

Question 5

How are FAs released from TAG in adipocytes?

Answer 5

by hormone sensitive lipase which are triggered by phosphorylation by epinephrine

Question 6

How does the beta oxidation pathway degrade fatty acids?

Answer 6

2 carbons at a time

Question 7

What are the 3 stages of beta oxidation?

Answer 7

• activation
• transport
• degradation

Question 8

Where does the activation stage occur?

Answer 8

the cytosol

Question 9

What happens in the activation stage?

Answer 9

fatty acid activated to form fatty acyl coA in cytoplasm

Question 10

What happens in the transport stage of beta oxidation? Basics

Answer 10

transport of fatty acyl coA from cytosol into matrix of the mitochondrion by mechanism of the carnitine shuttle

Question 11

How is fatty acyl coA transferred from the cytosol to the matrix by the carnation shuttle?

Answer 11

• fatty acylcoA loses the coA and is transferred by the CAT-1 enzyme into the mitochondrion
• in the matrix, the fatty acyl recombines with a CoA

Question 12

What inhibits the carnitine shuttle?

Answer 12

malonyl coA

Question 13

What is the significance of the regulatory action of the presence of malonyl CoA?

Answer 13

prevents synthesis and degradation happening at the same time

Question 14

What is CAT-1 deficiency?

Answer 14

no beta oxidation occurs resulting in hypoglycaemia

Question 15

How is CAT-1 deficiency hypoglycaemia treated?

Answer 15

IV glucose

Question 16

What is the therapy for a CAT-1 deficiency?

Answer 16

give medium chain fatty acids that do not require CAT for mitochondrial transport

Question 17

There are 4 stages to the final stage of beta oxidation. What are they? Degradation

Answer 17

1. dehydrogenation to produce FADH2
2. Hydration
3. Dehydration to produce NADH
4. Thiolysis (leaved) to produce acetyl coA

Question 18

What is produced in each beta oxidation cycle?

Answer 18

one acetyl CoA and a species two carbons shorter than the original (keeps occurring with 2 carbons chopped off each time)
also FADH2 and NADH

Question 19

How much energy in ATP is produced from beta oxidation of palmitate?

Answer 19

129

only 32ATP produced per molecule of glucose!

Question 20

What length of fatty acids undergo preliminary beta oxidation in the peroxisome?

Answer 20

> 22 carbons

Question 21

What is a disadvantage of having to have preliminary beta oxidation?

Answer 21

first step doesn’t produce FADH2 and so less energy efficient

Question 22

What happens to excess acetyl CoA from beta oxidation?

Answer 22

cannot convert acetyl CoA into glucose
in fasting/starvation is converted to ketone bodies or enters the citric acid cycle to be converted to oxaloactetate which can be used in gluconeogenesis

Question 23

What does acetyl CoA inhibit and what does it do?

Answer 23

inhibits pyruvate dehydrogenase which is the enzyme responsible for converting pyruvate to Acetyl CoA

Question 24

What does Acetyl CoA activate and what does it do?

Answer 24

activates pyruvate carboxylase which converts pyruvate to oxaloacetate which can be used in gluconeogenesis

Question 25

What organs use ketone bodies as fuel during starvation?

Answer 25

brain cells

cardiac and skeletal muscle

Question 26

Where are ketone bodies formed?

Answer 26

in the liver in the mitochondrial matrix

Question 27

How are ketone bodies transported for use elsewhere in the body?

Answer 27

liver can’t use ketone bodies

soluble in blood so don’t require albumin for transport