Lipid Metabolism

Question 1

Which enzyme breaks down chylomicrons and VLDL to release fatty acids which are taken up by cells?

Answer 1

Lipoprotein lipase

Question 2

To which plasma protein are free fatty acids bound?

Answer 2

Albumin

Question 3

Which enzymes are responsible for the movement of fatty acyl-coA into the mitochondria from beta oxidation to occur?

Answer 3

Carnitine palmitoyltransferase (CPT) one and two

Question 4

Where in the cell does beta oxidation occur?

Answer 4

mitochondria

Question 5

From which amino acids is carnitine derived?

Answer 5

Lysine and methionine

Question 6

Each round of beta oxidation degrades fatty acyl-coA two carbons at a time. What does this produce?

Answer 6

1 FADH2
1 NADH
1 acetyl coA

Question 7

How is beta oxidation used to produce energy?

Answer 7

Fatty acyl-coA is degraded two carbons at a time to produce FADH2, NADH and acetyl co A. Acetyl co A is used in the TCA cycle to produce ATP and FADH2 and NADH are used in oxidative phosphorylation to produce ATP

Question 8

Fatty acids can be broken down from chylomicrons and VLDL in order to transport them into the cell. Once in the cell, which enzyme is responsible for re-esterifying these fatty acids to produce TAG?

Answer 8

DIacylglycerol acyl transferase (DGAT)

Question 9

Which enzyme is responsible for the breakdown of TAG (lipolysis) into glycerol and fatty acids?

Answer 9

Hormone sensitive lipase

Question 10

How is hormone sensitive lipase activated by sympathetic fibres?

Answer 10

Adrenaline activates cAMP dependent phosphorylation of hormone sensitive lipase in order to activate it

Question 11

How does insulin inhibits lipolysis?

Answer 11

By inhibiting the activation of hormone sensitive lipase by cAMP

Question 12

What is the maximum number of carbons that can be used in fatty acid synthesis by the body?

Answer 12

16

Question 13

What are the key regulatory enzymes in the process of fatty acid synthesis?

Answer 13

Acetyl coA carboxylase

Fatty acid synthase

Question 14

What is the product of the enzyme acetyl co A carboxylase in fatty acid synthesis and why is this significant?

Answer 14

Malonyl coA - this acts to inhibit the action of CPTto inhibit the transport of fatty acids into the mitochondria to prevent beta oxidation

Question 15

What is the action of fatty acid synthase?

Answer 15

This is a multifactorial enzyme which regulates seven successive steps in the process of fatty acid synthesis

Question 16

Fatty acid synthesis requires NADPH. Where does this come from?

Answer 16

The pentose phosphate pathway

Question 17

What are the three ketone bodies produced from metabolism of lipids?

Answer 17

Acetone
Beta-hydroxybutyrate
Acetoacetate

Question 18

The production of ketone bodies occurs as an overflow pathway when there is excessive amount of acetyl coA or not enough oxaloacetate. T/F?

Answer 18

True

Question 19

How is the ketone body acetoacetate produced?

Answer 19

Combining two acetyl coA molecules then removing a co A molecule

Question 20

How are beta-hydroxybutyrate and acetone produced?

Answer 20

By conversion from acetoacetate

Question 21

If a patient is undergoing ketosis, what will their breath smell like?

Answer 21

Sweet

Question 22

The first steps of phospholipid synthesis are the same as for TAG synthesis. DAG from this process is then combined with what substance to produce a phospholipid?

Answer 22

an alcohol

Question 23

There are high levels of phospholipid synthesis in rapidly diving cells. Why?

Answer 23

Phospholipids are needed to build new cell membranes

Question 24

Why are omega-3 and omega-6 fatty acids important?

Answer 24

Because they are essential fatty acids - they cannot be synthesised by the body

Question 25

What are the functions of essential fatty acids?

Answer 25

Cell membrane formation
Use as precursors for eicosanoids (prostanoids and leukotrienes)
Required for proper growth and development
Required for brain and nerve function

Question 26

It is thought that omega-3 and omega-6 fatty acids have potential cardiovascular benefits. What are these?

Answer 26

Omega three is thought to protect against heart and circulatory disease and reduce plasma TAG
Omega 6 is through to lower LDL

Question 27

Which enzymes does insulin stimulation in order to stimulation the storage of TAG?

Answer 27

Lipoprotein lipase

Acetyl coA carboxylase

Question 28

In the fed state, what tissues is LPL active in and in which tissue is it inactive?

Answer 28

Active in adipose to promote TAG storage

Inactive in skeletal and cardiac muscle

Question 29

In the fasted state or when exercise, in which tissue is LPL active and in which is it inactive?

Answer 29

Inactive in adipose

Active in muscle to provide more fatty acids for the purpose of ATP generation

Question 30

When their is overreaction of lipolysis or TAG storage capacity in adipose tissue is exceeded, where are fatty acid taken up and stored and why is this significant?

Answer 30

In the liver and muscle

This is significant as it interferes with insulin signalling