Fatty Acid Synthesis

Question 1

Primary tissues for fatty acid synthesis

Answer 1

Liver*, kidney, brain, lung, mammary glands, adipose

Question 2

Where does fatty acid sythesis occur in the cell?

Answer 2

Cytosol

Question 3

What are fatty acids synthesised from?

Answer 3

acetyl-CoA

Question 4

What is the main source of acetyl-CoA?

Answer 4

Glucose

Question 5

Major enzymes in fatty acid synthesis

Answer 5

Acetyl-CoA carboxylase, Fatty Acid synthase

Question 6

From what is citrate formed?

Answer 6

Acetyl-CoA and OAA

Question 7

Citrate lyase

Answer 7

Cleaves citrate into Acetyl-CoA and OAA. Is only found in the cytosol.

Question 8

How is pyruvate formed from OAA in the cytosol?

Answer 8

Cytosolic malate DH forms malate, malic Ez forms pyruvate from malate

Question 9

Formation of Malonyl CoA

Answer 9

Acetyl CoA carboxylase uses CO2 and ATP to make Acetyl CoA into Malonyl CoA

Question 10

What activates acetyl CoA carboxylase?

Answer 10

Insulin (activates protein phosphatase)

Question 11

What stimulates AMPK?

Answer 11

AMP, AMPK covalant (via Glucagon or Epi). Inhibits aceytl-CoA Carboxylase

Question 12

Long-term “adative” regulation

Answer 12

Long high calories=increased synthesis of Acetyl CoA Carboxylase. Long low calorie=decreased synthesis of acetyl CoA carboxylase

Question 13

What are the starting and ending units of fatty acid synthase?

Answer 13

acetyl-CoA starts, 2 carbons added at a time, product is palmitate

Question 14

Acetyl transacylase

Answer 14

Adds acetyl group on #1 monomer

Question 15

Malonyl transacylase

Answer 15

Adds malonyl group on monomer #2

Question 16

3-ketoacyl synthase

Answer 16

Makes a 3-ketoacyl, causes decarboxylation, passes carbons from one monor to the other (back and forth)

Question 17

3-ketoacyl reductase

Answer 17

Reduces 3 ketoacyl to 2 hydroxy using NADPH

Question 18

Hydratase

Answer 18

Removes H2O to form a 2-enyol group

Question 19

Enoyl reductase

Answer 19

Saturates the CC double bonem uses NADPH, leaves a saturated acyl

Question 20

Thioesterase

Answer 20

Breaks off acyl group to leave palmitate

Question 21

Acyl-CoA synthase

Answer 21

converts palmitate to palmitoyl-CoA to allow further reactions

Question 22

What is a major source of NADPH?

Answer 22

pentose phosphate pathway

Question 23

Where does fatty acid elongation take place?

Answer 23

ER

Question 24

What are the preferred substrates and products of fatty acid elongation?

Answer 24

Palmitoyl-CoA is substrate. Product is stearoyl-CoA (18C)

Question 25

Why is elongation a separate process fron synthesis?

Answer 25

There are different enzymes doing the same process

Question 26

Formation of monosaturated fatty acids

Answer 26

in the ER. Stearoyl-CoA desaturase. Desaturation always occurs at C9. Product is oleoyl CoA* or palmitoleoyl-CoA (stearoyl is preferred).

Question 27

Functions of polyunsaturated fatty acids

Answer 27

increases membrane fluidity, source of eicosanoids

Question 28

What carbons can humans desaturate?

Answer 28

4,5,6, and 9. CANNOT desaturate Beyond* C9

Question 29

What are omega fatty acids?

Answer 29

Fatty acids counted from the furthest C, instead of the alpha carbon

Question 30

Why are omega 3 and 6 necessary for dietary intake?

Answer 30

Cannot synthesize past C9, so must be taken in via diet