Fatty Acid Catabolism

Question 1

fatty acid catabolism is called

Answer 1

Fatty acid beta-oxidation

Question 2

Fatty acid beta-oxidation occurs in 3 main stages

Answer 2

1. Fatty acid activation (occurs in the cytosol in the cell)
   - Coenzyme A is added to the fatty acid to form acyl CoA, which is the activated form of fatty acid.
2. Fatty acid transportation from the cytosol to the mitochondrial matrix.
   - Acyl CoA cannot be transported across the mitochondrial membrane, so it must be converted to acyl carnitine. This molecule can transport across the outer mitochondrial matrix, but needs help from acyl carnitine translocase to cross the inner membrane.
3. Fatty acid oxidation (occurs in the mitochondrial matrix)
   - Acyl Carnitine is converted back to Acyl CoA and it is ready to be oxidized. Each cycle of oxidation removes 2 carbons from the fatty acid chain, and those 2 carbonic an be converted into acetyl CoA. Each cycle of oxidation transfers electrons to 1 NAD+ and 1 FAD. They are reduced to NADH and FADH2.

Question 3

Each cycle of oxidation removes __ carbons from fatty acid chains. The __ carbons are converted to acetyl coA

Answer 3

2, 2.

Question 4

Explain all the different conversions fatty acid goes through

Answer 4

Cytosol: Fatty acid + coenzyme A = Acyl CoA (activated form of FA)

2 steps of moving across MM:
1. Acyl CoA –> Acyl Carnitine (passes through OMM)

2. Acyl Carnitine + Acyl Carnitine Translocase (passes through IMM)

Mitochondrial matrix: Acyl Canitine –> Acyl CoA

Acyl CoA is oxidized and results in 1 Acetyl CoA and 1 electron for NAD+ and one electron for FAD per every 2 carbons oxidized on the fatty acid chain.

Question 5

NADH carrying 1 electron produces how much ATP?

Answer 5

1 electron x 2.5 = 2.5 ATP

Question 6

FADH2 carrying 1 electron produces how much ATP?

Answer 6

1 electron x 1. 5 = 1.5 ATP

Question 7

How many acetyl CoA are produced from a 16 carbon fatty acid molecule?

Answer 7

8. (2 carbons per acetyl coA)

This means that the citric acid cycle would have to occur 8 times in order to fully oxidize a 16 carbon fatty acid.

Question 8

How many NADH, FADH2, and GTP are produced during the citric acid cycle?

Answer 8

3 NADH produced
1 FADH2 produced
1 GTP produced

And 1 oxaloacetate and 2 Co2 **

Question 9

Oxaloacetate levels in individuals with Diabetes type 1

Answer 9

Oxaloacetate in the citric acid cycle is removed and used for gluconeogenesis instead. If oxaloacetate is absent from the citric acid cycle, it cannot join with acetyl CoA to produce Citrate. If this cannot occur, acetyl coA will build up and be converted to ketone bodies in the liver = ketoacidosis

Question 10

What happens if there is not sufficient amount of oxaloacetate to bind with acetyl coA? (Occurs when glucose is not present in cels).

Answer 10

The citric acid cycle is broken and Acetyl CoA levels will build up. Excess Acetyl CoA will converted in the liver to ketone bodies, which then enter the bloodstream. Ketone bodies are moderately acidic and can result in ketoacidosis, leading to dehydration, coma or death.

Question 11

3 examples of ketone bodies

Answer 11

Acetoacetate, B-hydroxybutyrate, acetone

Question 12

Ketone bodies can be used as a fuel source mainly by the

Answer 12

brain, heart, kidneys and skeletal muscles

Question 13

Normal ketone concentration in the blood vs ketone concentration for someone in ketoacidosis

Answer 13

0.5mg/dL = normal
If the ketone concentration in the blood exceeds 250 mg/dL, the result is ketoacidosis. Dehydration, coma, or death.

This mainly occurs in type 1 diabetics since glucose cannot enter their cells due to the lack in production of insulin.