Fat Breakdown and beta-oxidation

Question 1

Energy source from fat

Answer 1

Fats are a huge source of carbon molecules that can be used in the TCA cycle to produce energy

Question 2

Tryglyceride breakdown steps

Answer 2

1. Initiated by hormones (catecholamines, glucocorticoids, thyroid hormones) at the beta-receptor
2. beta-receptor activates adenylate cyclase, resulting in cAMP from ATP
3. cAMP activated protein kinase A
4. Protein kinase phosphorylates hormone sensitive lipase (activated)
5. Activated hormone sensitive lipase breaks down triglycerides into FFA and glycerol

Question 3

Transportation of FFA out of adipose tissue

Answer 3

FFA can be transported out of the adipose tissue by binding to albumin. They will be transported to the destination tissues, any excess will be recycled back to the liver.

Question 4

Where does the glycerol go from fat breakdown?

Answer 4

Glycerol is soluble and will be transported out of the cell by diffusion and will go back to the liver for use in gluconeogenesis

Question 5

insulin control of lipolysis

Answer 5

• Insulin inhibits glucocorticoids which decreases synthesis of hormone sensitive lipase
• Insulin inhibits phosphodiesterase, turning off cAMP production
• Insulin inhibits protein phosphatase 1, turning off hormone sensitive lipase, preventing break down of triglycerides into FFA’s

Question 6

Free fatty acid fates

Answer 6

FFA from adipose will either go to the destination tissues or if in excess it will go back to the liver in VLDL.

Question 7

Steatosis

Answer 7

Fatty Liver Disease

Occurs when there is an overproduction of fat breakdown and too much fat is being recycled back to the liver. Amount of fat is much greater than the amount that can be repackaged in VLDLs.

Question 8

Fatty acid prep for beta-oxidation when inside destination tissues

Answer 8

1. FFA are activated by binding to acyl-CoA (using acyl-CoA synthase) to make fatty acyl-CoA.
2. Fatty acyl-CoA binds to carnitine for transport into mitochondria
3. carnitine palmitoyltransferase removes carnitine from fatty acyl-CoA

Question 9

beta-oxidation steps

Answer 9

Fatty acid is cleaved 2Cs at a time making acetyl-CoA molecules for the TCA cycle.

Question 10

Payoff of beta-oxidation

Answer 10

Results in 1 NADH and 1 FADH2 for every cycle in beta-oxidation.

Each acetyl-CoA goes into TCA cycle and produces 1FADH2 and 3NADH