Lecture 26 - Fatty acids as a fuel molecule 2

Question 1

How are FFA transported in the blood and cytosol

Answer 1

• In blood; FFA are bound to albumin for transport
• In cytosol; Inside cells, FFA are carried by fatty acid binding proteins (FABPs)

Question 2

How are fatty acids activated for oxidation

Answer 2

• Fatty acids are activated by attaching to coenzyme (CoA) to form fatty acyl-CoA
• This reaction is driven by ATP hydrolysis, converting ATP to AMP, using the energy equivalent of 2 ATP molecules

Question 3

What is B oxidation and Where does it occur

Answer 3

B-oxidation is the process of breaking down fatty acids into acetly-COA units in the mitochondrial matrix, generating energy via reduction of NAD+ and FAD

Question 4

Products of B-oxidation

Answer 4

Each cycle:
1 NADH
1 FADH
1 acetyl-CoA

Question 5

What is the ATP cost of activating fatty acids for oxidation

Answer 5

Activation required hydrolysis of ATP and AMP, which equivalent to the energy of 2 ATP molecules

Question 6

How do fatty acids enter the mitochondria for B oxidation

Answer 6

• Fatty acly-CoA passes through the outer membrane via fatty acyl-CoA carrier
• For the inner membrane fatty acyl-CoA is converted to fatty acyl-carnitine by carnitine aclytransferase, allowing to cross into the mitochondrial matrix

Question 7

Role of FAD in B oxidation

Answer 7

FAD accepts 2 electron and 2 hydrogen atoms to form FADH2 in the first reaction of B oxidation, which conserves energy

Question 8

What are key reactions of B-oxidations

Answer 8

1. Oxidation: fatty acyl-coa is oxidised reducing FAD to FADH2
2. Hydration: Adding water, introducing OH group
3. Oxidation: NAD+ is reduced to NADH and extra H produced
4. Cleavage: The 2-carbon acetyl-coA is cleaved and the shortened Fatty acyl-coa enters the next cycle

Question 9

Overall reaction of B oxidation of palmitate

Answer 9

Palmitoyl-CoA + 7NAD+ + 7FAD + 7 CoA + 7H2O -> 8Acetyl-CoA + 7NADH + 7FADH2 + 7H+

Question 10

In which products is the energy released during B-oxidation captured

Answer 10

The energy is captured in the form of NADH, FADH2 and acetyl-CoA

Question 11

How many rounds of B oxidation are required to fully oxidise a 16-carbon fatty acid

Answer 11

7 rounds of B oxidation occur, producing 8 Acetyl-CoA

Question 12

What happens to the acetyl-CoA produced in B oxidation

Answer 12

Acetly-CoA enters the citric acid cycle for further oxidation, producing more energy in the form of NADH, FADH and ATP

Question 13

What is the role of carnitine in fatty acid oxidation

Answer 13

Carnitine is used to shuttle fatty acyl-coa across the inner member of mitochondria membrane by forming fatty acyl-carnitine, which can pass through specific transporters

Question 14

What are the sources of fatty acids used as fuels

Answer 14

Fatty acids come from the breakdown of TAG stored in adipose tissue or from dietary fats