Fatty acid and TG metabolism

Question 1

Rate of lipolysis in adipose tissue regulated by hormones_____

Answer 1

Insulin
Glucagon
Epinephrine
Cortisol

Question 2

How fatty acids are transported in mitochondria

Answer 2

• Fatty acid are not available in free form to transport
• requires activation by thiokinase enzyme + ATP
• Converts into acyl co-A to be transported into mitochondria

Small chain and medium chain FA can diffuse into mitochondria
Very long chain are broken down in peroxisomes to long chain FA which then transported via carnitine shuttle

Question 3

Carnitine shuttle

Answer 3

• Fatty acyl co A converted to fatty acyl carnitine by carnitine palmitoyl transferase I (CPT I) in outer membrane of mitochondria
• Fatty acyl carnitine transported into inner mitochondrial membrane by translocase enzyme
• where it gets converted into fatty acyl co A and free carnitine via CPT II which then undergoes B oxidation
• movement of free carnitine and fatty acyl carnitine follows antiport mechanism

Question 4

B oxidation substrate, enzyme and product

Answer 4

Substrate: Fatty acyl co A
Enzyme: Thiolase
Product: Acetyl Co A + NADH + FADH2 + fatty acyl co A with fewer carbon
Yield : for palmitate FA this cycle repeats for 7 times
producing 8 acetyl co A (80 ATP from TCA cycle) + 7 NADH + 7 FADH2 (28 ATP from both) = 108 ATP

Question 5

Metabolism of odd chain and branched chain fatty acid

Answer 5

Odd chain FA:
Eg: propionyl Co A converts into Succinyl co A – TCA cycle

Branched chain FA:
their B carbon is on the branch location – can’t be converted to ketone so under goes alfa-oxidation to produce acetyl co A (for ketogenesis) and propionyl co A (for succinyl co A to TCA cycle)

Question 6

Ketogenesis in Liver

Answer 6

formation of ketone bodies from acetyl co A via HMG Co A synthase and lyase present in liver
substrate: acetyl co A
enzyme: HMG Co A synthase and Lyase
product: Co A (for fat metabolism) + ketone bodies (acetoacetate, B hydroxybutyrate and acetone, for use by tissues).

Question 7

How ketone bodies are used to generate energy

Answer 7

substrate: acetoacetate and B hydroxybutyrate with succinyl Co A
Enzyme: succinyl co A:acetoacetate co A transferase, thiolase
Product: 2 x acetyl co A (for TCA cycle)

Question 8

Mobilization of lipids by hormone

Answer 8

Lipase converts TG to free FA (lipolysis process)
Lipase activity is increased by Glucagon and epinephrine to use free FA in gluconeogenesis
while insulin inhibits lipolysis and gluconeogenesis