Fatty Acid Synthesis/β-oxidation

Question 1

Where does fatty acid synthesis occur within the cell?

Answer 1

Cytosol

(of liver cells)

Question 2

Where does β-oxidation of fatty acids occur within the cell?

(breakdown of fatty acids)

Answer 2

Mitochondria

Question 3

Which fatty acid can be synthesized by humans and is the end product of fatty acid synthesis?

Answer 3

Palmitate

(16:0)

Question 4

Which enzyme is the rate-limiting enzyme of fatty acid synthesis?

Answer 4

Acetyl-CoA carboxylase

(needs ATP and biotin to function)

Question 5

What are the two important enzymes of fatty acid synthesis?

Answer 5

1. acetyl Co-A carboxylase
2. fatty acid synthase

Question 6

Mitochondrial acetyl-CoA must be transported to the cytosol for fatty acid synthesis. What carries mitochondrial acetyl-CoA into the cytosol?

Answer 6

Citrate shuttle

Question 7

In fatty acid synthesis, which enzyme activates acetyl-CoA in the cytosol for incorporation into fatty acids?

Answer 7

Acetyl-CoA carboxylase

acetyl-CoA → malonyl-CoA

Question 8

In fatty acid synthesis, the repetitive additions of malonyl-CoA continues until what happens?

Answer 8

Palmitate is formed.

(16:0)

Question 9

NADPH from the PPP has reducing power which is very important for fatty acid synthesis. What is its function in fatty acid synthesis?

Answer 9

NADPH reduces the acetyl groups added to fatty acids.

Question 10

In fatty acid synthesis, which molecule is the reducing agent?

Answer 10

NADPH

Question 11

What is the purpose of fatty acid synthesis? β-oxidation (or fatty acid oxidation)?

Answer 11

Fatty acid synthesis: convert acetyl-CoA into fatty acids

β-oxidation: breakdown fatty acids into acetyl-CoA

Question 12

The β-oxidation of fatty acids feeds electrons to which other pathway?

Answer 12

Electron transport chain

(NADH and FADH₂ are produced which are used to generate ATP in the ETC.)

Question 13

Which enzyme is the rate-limiting enzyme in β-oxidation of fatty acids?

Answer 13

Carnitine acyltransferase I

Question 14

In β-oxidation, what is responsible for transporting carnitine bound to acyl-CoA from the inner mitochondrial membrane to the mitochondrial matrix?

Answer 14

Carnitine transporter

Carnitine is bound to acyl-CoA forming acyl carnitine via carnitine acyl transferase I.

Question 15

Fatty acids cannot be converted into glucose, but odd-numbered fatty acids are an exception. Why?

Answer 15

Because at the end of β-oxidation they yield 1 acetyl-CoA and 1 propionyl-CoA. Propionyl-CoA is a precursor of succinyl-CoA (from the citric acid cycle) which can undergo gluconeogenesis.

(Propionic Acid Pathway)

Question 16

Which molecule is the end product of β-oxidation of fatty acids?

Answer 16

acetyl-CoA

Question 17

In β-oxidation of fatty acids, what inhibits the rate-limiting enzyme carnitine acyltransferase I?

Answer 17

malonyl-CoA