Integration of Metabolism

Question 1

Describe the Phosphagen system.

Answer 1

Used to quickly replenish ATP via the metabolism of phosphocreatine during exercise. During exercise, phosphocreatine is broken down by phosphocreatine kinase.

Question 2

Define energy charge and reducing power. How are they related to each other?

Answer 2

Energy charge is [ATP]:[ADP]. Reducing power is [NADH]:[NAD+]. They are inversely related.

Question 3

What signal molecule is secreted by the small intestine acts on the brain following a meal?

Answer 3

Cholecystokinin (CCK). Increases satiety.

Question 4

What signal molecule is secreted by the small intestine acts on the pancreas and brain following a meal?

Answer 4

Glucagon like peptide-1 (GLP-1). Increases insulin secretion and biosynthesis in pancreas. Increases satiety in brain.

Question 5

What peptide is secreted by the stomach before a meal and how does it act?

Answer 5

Ghrelin. Acts on the hypothalamus to stimulate appetite.

Question 6

What is leptin and how does it act?

Answer 6

A protein secreted by adipocytes in direct proportion to fat mass that suppresses hunger and stimulates energy expenditure. Acts on the hypothalamus. Receptors become desensitized in obese individuals.

Question 7

What is the “overall energy sensor in cells” and how does it work?

Answer 7

AMP-activated protein kinase (AMPK). Can bind both ATP and AMP, but is activated by AMP. When AMP is bound, it is activated and phosphorylates targets, leading to an increase in ATP production.