Fatty Acid Catabolism & The Citric Acid Cycle

Question 1

Which ONE of the following is the major storage form of fats?

A) Phospholipid
B) Cholesterol
C) Arachidonic Acid
D) Triacylglycerol
E) Laminin

Answer 1

D) Triacylglycerol

Question 2

Which ONE of the following biomolecules restricts untimely access to triacylglycerol mobilisation from adipocytes?

A) Glycerol
B) Perilipin
C) Lipoprotein
D) Serum Albumen
E) Diacylglycerol

Answer 2

B) Perilipin

Question 3

Which ONE of the following enzyme types when activated mobilises triacylglycerols?

A) Catalase
B) Synthase
C) Dehydrogenase
D) Lipase
E) Hydratase

Answer 3

D) Lipase

Question 4

Beta-oxidation occurs in which ONE of the following cellular locations?

A) Cytosol
B) Golgi
C) Mitochondria
D) Nucleus
E) Plasma Membrane

Answer 4

C) Mitochondria

Question 5

Which ONE of the following binds fatty acids in the bloodstream after they are released from adipocytes?

A) Serum Albumen
B) Glucose
C) Acetyl-CoA
D) Cholesterol
E) Glycogen

Answer 5

A) Serum Albumen

Question 6

Which ONE of the following enzymes activates a fatty acid to a fatty acyl-CoA?

A) Acyl-CoA Kinase
B) Acyl-CoA Phosphotase
C) Acyl-CoA Dehydrogenase
D) Acetyl-CoA Synthetase
E) Acyl-CoA Carboxylase

Answer 6

D) Acetyl-CoA Synthetase

Question 7

Which ONE of the following is the major regulatory enzyme in fatty acid catabolism?

A) Carnitine Acyl-Transferase-1
B) Acyl-CoA Dehydratase
C) Acyl-Phosphotase
D) Phosphofructokinase
E) Pyruvate Kinase

Answer 7

A) Carnitine Acyl-Transferase-1

Question 8

A 20 carbon fatty acyl-CoA will degrade to which one of the following number of Acetyl-CoA?

A) 8
B) 8
C) 12
D) 11
E) 10

Answer 8

E) 10

Question 9

How many of the following NADH and FADH2 are formed when a 16 carbon fatty acid undergoes complete beta-oxidation?

A) 6 NADH and 7 FADH2
B) 8 NADH and 8 FADH2
C) 12 NADH and 10 FADH2
D) 7 NADH and 7 FADH2
E) None of the above

Answer 9

D) 7 NADH and 7 FADH2

Question 10

Which ONE of the following enzymes in beta-oxidation can malfunction due to an inherited genetic mutation that is tested for at birth?

A) Acyl-CoA Dehydrogenase
B) Acyl-CoA Kinase
C) Acyl-CoA Hydratase
D) Acyl-CoA Phosphatase
E) Acetyl-CoA Synthetase

Answer 10

A) Acyl-CoA Dehydrogenase

Question 11

Where are fatty acids stored in higher vertebrates?

Answer 11

Stored at Triacylglycerols in Adipocytes

Question 12

What type of bond is involved in joining fatty acids to the glycerol backbone in TAGs?

Answer 12

Ester bonds

Question 13

What tissues use a lot of fatty acids for energy?

Answer 13

• Liver
• Heart
• Resting skeletal muscle

Question 14

Are fatty acids more or less reduced than glucose?

Answer 14

More reduced and less hydrated

Question 15

Why are TAGs a better storage form of energy than glycogen?

Answer 15

More reduced and less hydrated so can stockpile large quantities in adipocytes

Question 16

What enzymes cause the mobilisation of fatty acids from adipocytes?

Answer 16

Lipases

Hydrolyse ester linkages

Question 17

Describe how fatty acids are mobilised from adipocytes

Answer 17

• Adrenaline & Glucagon secreted in response to low blood sugar, and PKA activated
• PKA phosphorylates perilipins to open lipid droplet

Question 18

What do Triacylglycerol lipases do?

Answer 18

Degrade TAGs to liberate fatty acids

Question 19

What does fatty acid activation involve?

Answer 19

The adding of CoA on to fatty acid by Fatty Acyl-CoA Synthetase

Question 20

What transport system brings fatty acyls into mitochondria?
(Describe it)

Answer 20

• Fatty acyl-CoA bond hydrolysed by carnitine acyl-transferase-1 & fatty acid group attaches to -OH of carnitine
• Fatty acyl-carnitine enters mitochondrial matrix through carnitine transporter
• Fatty acyl group enzymatically transferred ito intramitochondrial CoA by carnitine acyl-transferase-2

Question 21

Describe the FOUR enzyme steps of Beta-Oxidation

Answer 21

1. Dehydrogenase - removes 2H+ to FAD to FADH2
2. Hydratase - H20 added
3. Dehydrogenase - removes 2H+ to NAD+ to NADH + H+
4. Thiolase - entry of CoA-SH to form Acetyl CoA

Each 2C of fatty acyl-CoA cleaved & converted to Acetyl-CoA

Question 22

How many FADs and NADs are reduced in the oxidation of 16C palmitoyl-CoA?

Answer 22

7 FADs & 7 NADs

Question 23

How many acetyl-CoAs are made from the degredation/oxidation of 16C palmitoyl-CoA?

Answer 23

8

Question 24

What is the outcome of genetic defects in Acyl-CoA dehydrogenase?

Answer 24

• low energy
• fat accumulation
• vomiting
• sleeplessness
• coma

Question 25

What is the major enzyme that controls fatty acid catabolism?

Answer 25

Acyl-CoA Dehydrogenase

Question 26

What are ketone bodies?

Answer 26

Alternative energy source used when glucose is not readily available

Question 27

What are the THREE ketone bodies?

Answer 27

1. Acetone
2. Acetoacetate
3. D-𝛽-Hydroxybutyrate

Question 28

Where are ketone bodies made mostly in the body?

Answer 28

Liver

Question 29

When does ketone body formation happen?

Answer 29

When carbohydrates are unavailable
* low carb diet
* starvation
* fasting
* untreated diabetes

Question 30

How do ketone bodies give energy?

Answer 30

• Acetyl CoA from 𝛽-oxidation can’t enter citric acid cycle so are converted to ketone bodies
• Exported as energy source to tissues that need it

Question 31

Is overproduction of ketone bodies dangerous?
Explain

Answer 31

Yes.
Blood pH decreases —> acidosis —> ketosis —> coma