Lecture 13 - Fatty Acid Synthesis Mechanism

Question 1

Step 1a

Answer 1

Acetyl CoA -> acetyl-ACP

Question 2

Enzyme of step 1a

Answer 2

Acetyl-CoA-ACP transacetylase

Question 3

Cofactor of step 1a

Answer 3

ACP-SH -> CoA-SH

Question 4

Step 2

Answer 4

Acetyl-ACP -> acetyl-synthase

Question 5

Enzyme of step 2

Answer 5

Beta-ketoacyl-ACP synthase

Question 6

Cofactor of step 2

Answer 6

Synthase-SH -> ACP-SH

Question 7

Step 1b

Answer 7

Malonyl-CoA -> malonyl-ACP

Question 8

Enzyme of step 1b

Answer 8

Malonyl-CoA-ACP transacetylase

Question 9

Cofactor of step 1b

Answer 9

ACP-SH -> CoA-SH

Question 10

Step 3

Answer 10

Malonyl-ACP + acetyl-synthase -> acetoacetyl-ACP

Question 11

What is another name for acetoacetyl-ACP?

Answer 11

Beta-ketoacyl-ACP

Question 12

Enzyme of step 3

Answer 12

Beta-ketoacyl-ACP synthase

Question 13

Cofactor of step 3

Answer 13

CO2 + Synthase-SH out

Question 14

Describe what happens in step 1a

Answer 14

Acyl carrier protein attaches to the first acetyl CoA

Question 15

Describe what happens in step 2

Answer 15

Acetyl CoA group gets shifted to the fatty acid synthase enzyme

Question 16

Describe what happens in step 1b

Answer 16

Malonyl CoA (from acetyl CoA and CO2) is attached to ACP

Question 17

Describe what happens in step 3

Answer 17

Acetyl group (from acetyl synthase) is attached to the first acetate group (from malonyl-ACP), releasing the CO2 and synthase site

Question 18

Step 4

Answer 18

Acetoacetyl-ACP -> beta-hydroxyacyl-ACP

Question 19

What is another name for beta-hydroxyacyl-ACP?

Answer 19

Beta-hydroxybutyryl-ACP

Question 20

Enzyme of step 4

Answer 20

Beta-ketoacyl-ACP reductase

Question 21

Cofactor of step 4

Answer 21

NADPH + H+ -> NADP+

Question 22

Step 5

Answer 22

Beta-hydroxyacyl-ACP -> butenoyl-ACP

Question 23

What is another name for butenoyl-ACP?

Answer 23

Trans-delta2-enoyl-ACP

Question 24

Enzyme of step 5

Answer 24

Beta-hydroxyacyl-ACP dehydratase

Question 25

Cofactor of step 5

Answer 25

H2O out

Question 26

Describe what happens in step 4

Answer 26

Reduction of the double bond with NADPH

Question 27

Describe what happens in step 5

Answer 27

Removal of H2O, producing a trans double bond

Question 28

Step 6

Answer 28

Butenoyl-ACP -> butyryl ACP

Question 29

Step 7

Answer 29

Butyryl ACP -> hexanoyl-ACP (beginning of a new cycle; butyryl ACP is equivalent to acetyl-CoA)

Question 30

Enzyme of step 6

Answer 30

Enoyl-ACP reductase

Question 31

Cofactor of step 6

Answer 31

NADPH + H+ -> NADP+

Question 32

Describe what happens in step 6

Answer 32

Second reduction using NADPH, removing the double bond

Question 33

What is the last step of fatty acid synthesis?

Answer 33

Palmitoyl-ACP -> palmitate

Question 34

Enzyme of step 8 (last step)

Answer 34

Palmitoyl-ACP thioesterase

Question 35

Cofactor of step 8 (last step)

Answer 35

H2O -> ACP-SH

Question 36

What is the overall reaction that takes place in fatty acid synthesis?

Answer 36

8 acetyl-CoA + 7 ATP + 14 NADPH/H+ -> 1 palmitic acid

Question 37

Where do the carbons for fatty acid synthesis come from?

Answer 37

Acetate and malonate, but malonate originates as acetate, so all carbons come from acetate