Fatty Acid Synthesis

Question 1

Where in the body is lipogenesis particularly important?

Answer 1

• Adipose
• Liver
• Lactating mammary

Question 2

Where does lipogenesis occur?

Answer 2

In the cytoplasm

Question 3

Where is acetyl-CoA made?

Answer 3

In the mitochondria

Question 4

How is acetyl-CoA transported into the cytosol?

Answer 4

Via the citrate shuttle

Question 5

Which enzyme catalyses the formation of malonyl-CoA from acetyl-CoA?

Answer 5

Acetyl-CoA carboxylase

Question 6

What acts as a cofactor for Acetyl-CoA carboxylase?

Answer 6

Biotin

Question 7

Give the reaction for the carboxylation of acetyl-CoA to form malonyl-CoA

What is often the source of CO₂ in this reation?

Answer 7

acetyl-CoA + CO₂ + ATP → malonyl-CoA + ADP + P_i

Usually comes from bicarbonate

Question 8

Which enzyme is responsible for the synthesis of fatty acids?

Answer 8

Fatty Acid synthase

Question 9

Where do acetyl-CoA and malonyl-CoA bind on fatty acid synthase?

Answer 9

Bind to sulphydryl group of an acyl carrier protein

Question 10

Overall how many NADPH are required to produce 1 molecule of palmitate?

Answer 10

14

Question 11

Where is palmitate further elongated and desaturated?

Answer 11

Smooth endoplasmic reticulum

Question 12

What happens to the fatty acid when a 16 carbon fatty acid chain is formed?

Answer 12

It drops off fatty acid synthase

Question 13

How is fatty acid synthesis regulated in the short term?

Answer 13

• Control of pyruvate dehydrogenase and glucose uptake controls substrate supply
• Inhibition/activation of acetyl-CoA carboxylase

Question 14

What allosterically activates Acetyl-CoA carboxylase?

Answer 14

Citrate

Question 15

What inhibits Acetyl-CoA carboxylase?

Answer 15

Palmitoyl-CoA

Question 16

Which enzymes are regulated in the long term via hormonal and nutrient control?

Answer 16

• Acetyl-CoA carboxylase
• Fatty acid synthase
• Pentose phosphate pathway enzymes

Question 17

What kind of diet induces expression of Acetyl-CoA carboxylase?

Answer 17

High carb

Question 18

What is cholesterol synthesised from?

Answer 18

Acetyl-CoA

Question 19

Which enzyme is involved in the production of cholesterol?

Answer 19

HMG-CoA reductase

Question 20

How is HMG-CoA reductase regulated in the short term?

Answer 20

End product allosteric inhibition by cholesterol

Question 21

How is HMG-CoA reductase regulated in the long term?

Answer 21

Cholesterol inhibits expression of HMG-CoA (at a gene level)

Question 22

What drugs inhibit HMG-CoA reductase?

Answer 22

Statins

Question 23

How are lipids transported into the blood?

Answer 23

In association with proteins as lipoprotein particles

Question 24

What makes up lipoproteins?

Answer 24

• Cholesterol
• Apolipoproteins
• Phospholipids
• Triacylglycerol and cholesteryl esters

Question 25

What are the roles of apolipoproteins?

Answer 25

* Structural * Ligands for receptors * Activators for enzymes involved in metabolism of lipoprotein particles

Question 26

Where are chylomicrons formed in exogenous lipid transport?

Answer 26

In cells that line the gut

Question 27

Which apoproteins are transported onto chylomicrons in the exogenous lipid transport mechanism?

Answer 27

C11 and E

Question 28

What is the purpose of C11 in the exogenous lipid transport pathway?

Answer 28

Activates lipoprotein lipase on the surface of capillaries causing the hydrolysis of TAGs to glyceol and non-esterified fatty acids

Question 29

What is the purpose of Non-essential fatty acids?

Answer 29

They enter cells fro metabolism/storage

Question 30

What happens to C11 once it has activated lipoprotein lipase?

Answer 30

It is transferred back to HDL

Question 31

Why does the proportion of cholesterol increase in remnant chylomicron?

Answer 31

due to the depletion of triglycerides

Question 32

Where is the CM remnant taken up?

Answer 32

In the liver

Question 33

Which receptors in the liver allow CM remnant to be taken up?

Answer 33

B48 and E

Question 34

In endogenous lipid transport what picks up lipoproteins from HDL?

Answer 34

VLDL

Question 35

In the circulation what does IDL become?

Answer 35

LDL

Question 36

What type of lipoprotein can be taken up by the unregulated cholesterol pathway?

Answer 36

Modified LDL

Question 37

What controls the expression of the gene for LDL receptor?

Answer 37

The amount of cholesterol in the cell

Question 38

What are the functions of HDL?

Answer 38

* Provides apoproteins for other lipoproteins * Mops up cholesterol from peripheral tissues

Question 39

What can hyperlipidaemias occur as a result of?

Answer 39

* enzyme deficiency * apoprotein deficiency * receptor deficiency

Question 40

What type of immune cell is involved in atherosclerosis?

Answer 40

Macrophages

Question 41

What do macrophages ingest in the process of atherosclerosis?

Answer 41

Oxidised lipoproteins

Question 42

Outline the process of atherosclerosis

Answer 42

* oxidised lipoproteins aggregate and stick to the extracellular matrix * Macrophages are attracted and ingest lipoproteins * Free cholesterol accumulates in macrophages * Apoptosis, necrosis and tissue damage occurs * A cholesterol-rich plaque forms