Lipids 3

Question 1

Where does fatty acid synthesis occur?

Answer 1

liver
lactating mammary gland
adipose tissue

Question 2

What are fatty acids synthesised from?

Answer 2

from acetyl CoA derived from excess protein, fat and carbohydrate

Question 3

What part of the cell does fatty acid synthesis occur in?

Answer 3

cytosol

Question 4

Acetyl CoA is formed in the matrix of the mitochondrion and so has to be transferred out into the cytosol. How does this occur?

Answer 4

via the citrate shuttle when citrate concentration in mitochondrion is high

Question 5

What 2 enzymes are required for fatty acid synthesis?

Answer 5

Acetyl CoA carboxylase (activation/regulation)

Fatty acid synthase (multifunctional enzyme)

Question 6

What is required for fatty acid synthesis?

Answer 6

enzymes

acetyl CoA and NADPH

Question 7

What is produced from fatty acid synthesis?

Answer 7

palmitic acid

Question 8

What does acetyl CoA carboxylase do?

Answer 8

forms Malonyl CoA by adding CO2 to acetyl CoA which is the committed step in fatty acid synthesis

Question 9

What are the key regulators of the activity of acetyl CoA carboxylase?

Answer 9

activated by citrate (signals that there is enough glucose)
deactivated by palmitoyl CoA
insulin activates
glucagon and epinephrine deactivate

Question 10

What happens in elongation of malonyl coA?

Answer 10

Acetoacyl-ACP is formed from Acyl-malonyl ACP condensing

Question 11

What is acetoacetyl-ACP?

Answer 11

complex of acyl-malonyl and ACP enzyme

Question 12

What happens to the acetoacyl-ACP?

Answer 12

carbons are added 2 at a time with the enemy acting as an ‘arm’ sweeping to pick up these carbons. Palmityl-ACP is formed

Question 13

What does thioesterase do?

Answer 13

cleaves palmityl CoA from the ACP

Question 14

What does the multifuctional fatty acid synthase enzyme do?

Answer 14

Works with the ACP to catalyse the formation of long chain fatty acids.
Is a series of 7 enzymes that the ACP arm swings the acyl-malonyl round to catalyse reactions to extend the chain

Question 15

How much NADPH is required for the formation of palmitate and where do we get the NADPH?

Answer 15

14

from the pentose phosphate pathway

Question 16

Where does any extra modification of palmitate or dietary fatty acids occur?

Answer 16

in mitochondria and ER by diverse enzymes

Question 17

What are steroid hormones?

Answer 17

chemical substances that serve as chemical messengers in the body

Question 18

What is the starting material for the formation of steroid hormones?

Answer 18

cholesterol

Question 19

What are eicosanoids?

Answer 19

signalling molecules derived from 20 carbon unsaturated fatty acids (omega 3) and are synthesised throughout the body

Question 20

What is the function of cholesterol?

Answer 20

component of cell membranes

precursor to other substances e.g. sterol hormones, vitamin D, bile acids

Question 21

Where is cholesterol made?

Answer 21

mainly in the liver

Question 22

What do statins do?

Answer 22

inhibit enzyme responsible for cholesterol synthesis and lower LDL levels

Question 23

What do eicosanoids regulate?

Answer 23

inflammatory response
pain and fever
blood pressure
blood clot induction
labour induction
sleep/wake cycle etc

Question 24

What are COX inhibitors?

Answer 24

aspirin

anti-inflammatory and fever-reducing property due to inhibition of COX1 enzyme and prostaglandin synthesis

Question 25

What are eicosanoids precursors to?

Answer 25

prostaglandins, leukotrienes and thromboxanes