Lecture 15 - Energy Balance and Metabolim II

Question 1

What compartments do the ornithine (urea) cycle occur in and what are the net reactions?

What intermediate is formed that can enter the citric acid cycle?

RL15 S74

Answer 1

Mitochondria:

• ammonia + CO2 -> carbamoyl phosphate
• carbamoyl phosphate + ornithine -> citruline

Cytoplasm (net reaction):
-citruline + aspartate -> urea and ornithine

Fumarate can enter the citric acid cycle

Question 2

What is the major rate-limiting factor for most all energy metabolism?

RL15 S76

Answer 2

ADP

Question 3

What is one of the best known factors that affects metabolic rate?

RL15 S78

Answer 3

Cold; increases TSH which increases metabolic activity

Question 4

What affect does thyroxine, testosterone, and malnutrition have on BMR?

RL15 S80

Answer 4

Thyroxine:

• increase: +50-100% BMR
• decrease: -40-60% BMR

Testosterone:
-increase: +10-15%

Malnutrition:
-marked reduction in BMR