Fatty Acid Biosynthesis

Question 1

Where does lipid biosynthesis primarily occur?

Answer 1

Cytosol (primarily liver, some adipose)

Lipid biosynthesis takes place mainly in the liver and to some extent in adipose tissue.

Question 2

What is the main enzyme complex responsible for fatty acid synthesis?

Answer 2

Fatty acid synthase

Fatty acid synthase is a multi-enzyme complex that catalyzes the synthesis of fatty acids.

Question 3

What is the final product of fatty acid synthesis?

Answer 3

Palmitate (16C)

The synthesis process continues until palmitate, a 16-carbon fatty acid, is produced.

Question 4

What substrate is used for fatty acid synthesis?

Answer 4

Acetyl CoA

Acetyl CoA serves as the primary substrate for the synthesis of fatty acids.

Question 5

How is Acetyl CoA generated for fatty acid synthesis?

Answer 5

Citrate from TCA cycle

Citrate acts as a donor of Acetyl CoA, particularly when the body is in a high-energy state.

Question 6

What shuttle is used to transport citrate into the cytoplasm?

Answer 6

Citrate shuttle

The citrate shuttle allows citrate to cross the mitochondrial membrane, but Acetyl CoA cannot.

Question 7

What enzyme cleaves the acetyl group off citrate?

Answer 7

ATP-Citrate lyase

ATP-Citrate lyase is responsible for cleaving the acetyl group from citrate after it enters the cytoplasm.

Question 8

What is produced when malate is oxidized by malic enzyme?

Answer 8

NADPH

The oxidation of malate by malic enzyme yields NADPH, which is essential for fatty acid synthesis.

Question 9

What is the first rate-limiting step of fatty acid synthesis?

Answer 9

Acetyl CoA Carboxylase

Acetyl CoA Carboxylase converts Acetyl CoA to Malonyl CoA and is an irreversible step in the process.

Question 10

What does Acetyl CoA Carboxylase convert Acetyl CoA into?

Answer 10

Malonyl CoA

Malonyl CoA is the activated form of Acetyl CoA needed for fatty acid elongation.

Question 11

What is the role of Acyl Carrier Protein (ACP) in fatty acid synthesis?

Answer 11

Carries the growing fatty acid chain

ACP is essential for the transport and elongation of the fatty acid during synthesis.

Question 12

How does the fatty acid synthase complex know when the chain has reached 16 carbons?

Answer 12

It recognizes the length of the chain

The complex has a mechanism to sense when the fatty acid chain has reached the desired length of palmitate.

Question 13

How many NADPH molecules are consumed during the synthesis of palmitate?

Answer 13

14 NADPH

A total of 14 NADPH molecules are required for the synthesis of palmitate.

Question 14

Where does fatty acid elongation occur?

Answer 14

Endoplasmic Reticulum (ER)

Fatty acid elongation occurs in the ER, where specific enzymes are located.

Question 15

What happens to Malonyl CoA during fatty acid elongation?

Answer 15

Adds 3 carbons, but CO2 leaves, making it 2 carbons

During elongation, Malonyl CoA contributes to the fatty acid chain, but the loss of CO2 reduces the net carbon count.

Question 16

What type of bonds do desaturases introduce during desaturation?

Answer 16

Cis bonds

Desaturases are specific enzymes that introduce cis double bonds into fatty acids at designated locations.

Question 17

What is the highest number of double bonds humans can introduce into fatty acids?

Answer 17

19

Humans can introduce up to 19 double bonds into fatty acids through desaturation.

Question 18

What are the two essential fatty acids mentioned?

Answer 18

• Linoleate
• Alpha-linolenate

These essential fatty acids are precursors for other long-chain polyunsaturated fatty acids.

Question 19

What is AMP-activated Protein Kinase’s role in fatty acid regulation?

Answer 19

Phosphorylates enzymes

AMP-activated Protein Kinase regulates fatty acid metabolism by phosphorylating key enzymes involved in the process.