L34- Integration of Metabolism

Question 1

What is the preferred metabolic fuel for skeletal muscle at rest?

Answer 1

Fatty acids.

Question 2

What is the preferred metabolic fuel for skeletal muscle at work?

Answer 2

Glucose.

Question 3

What is the preferred metabolic fuel for the heart?

Answer 3

Fatty acids.

Question 4

What is the preferred metabolic fuel for the brain?

Answer 4

Glucose (and ketone bodies during starvation).

Question 5

Which type of enzymatic regulation typically involves a fast response that can change the concentration and activity of enzymes already present and functioning?

Answer 5

Allosteric regulation.

Question 6

Addition or removal of a phosphate group to an enzyme is an example of what type of enzymatic regulation?

Answer 6

Covalent regulation.

Question 7

What type of enzymatic regulation involves synthesis or degradation of enzymes?

Answer 7

Inducible enzyme regulation.

Question 8

Name seven enzymes that are activated during a state of starvation.

Answer 8

Gluconeogenesis enzymes: glucose-6-phosphatase, fructose-2,6-bisphosphatase, pyruvate carboxykinase, phosphoenolpyruvate carboxykinase (PEPCK). FA oxidation enzymes: hormone-sensitive lipase, carnitine acyl transferase. Glycogenolysis enzymes: glycogen phosphorylase. Note that for our purposes, all other enzymes are active during the well-fed state.

Question 9

Which pancreatic hormone is released by the beta-cells of the pancreas after a meal?

Answer 9

Insulin.

Question 10

Which pancreatic hormone is released by the alpha-cells of the pancreas during starvation?

Answer 10

Glucagon.

Question 11

What is the metabolic function of insulin?

Answer 11

It promotes fuel storage and tissue growth after a meal.

Question 12

What is the metabolic function of glucagon?

Answer 12

It mobilizes fuels during a state of starvation (between meals).

Question 13

What is the metabolic function of epinephrine?

Answer 13

It mobilizes fuels during acute distress.

Question 14

Which hormone changes the kind of metabolic fuels recruited for energy over long term starvation?

Answer 14

Cortisol.

Question 15

What metabolic pathways are positively affected by insulin?

Answer 15

Glycogen storage in liver and muscle, fatty acid storage and synthesis, amino acid uptake and protein synthesis.

Question 16

What metabolic pathways are positively affected by glucagon?

Answer 16

Gluconeogenesis, glycogenolysis, fatty acid oxidation and release from adipose tissue.

Question 17

What metabolic pathways are positively affected by epinephrine?

Answer 17

Glycogenolysis, and fatty acid oxidation and release from adipose tissue. Note that epinephrine does not affect gluconeogenesis.

Question 18

What metabolic pathways are positively affected by cortisol?

Answer 18

Amino acid mobilization and breakdown, gluconeogenesis (from amino acid breakdown), and fatty acid oxidation and release from adipose tissue.

Question 19

Glucagon and epinephrine bind to a 7-transmembrane receptor and activate a signaling cascade that typically involves which secondary messenger?

Answer 19

cAMP (via activation of adenyl cyclase).

Question 20

The insulin receptor belongs to which class of receptors?

Answer 20

Tyrosine kinase receptors.

Question 21

True or False. Akt is involved in the insulin signaling cascade and regulates the translocation of the GLUT4 receptor to plasma membranes.

Answer 21

True.

Question 22

What are the three domains of steroid hormone receptors?

Answer 22

Hormone binding domain, DNA binding domain, and transcriptional activation domain.

Question 23

Which protein associated with steroid hormone receptors prevents nuclear translocation when the receptor is not bound to a hormone?

Answer 23

Heat shock protein 90 (hsp90).

Question 24

What is our primary storage fuel?

Answer 24

Triglycerides (fat).

Question 25

How long does it take for an individual to deplete liver glycogen stores?

Answer 25

12-18 hours.

Question 26

Stored triglycerides can provide fuel for up to how many days in a starving individual?

Answer 26

60

Question 27

What fuels are used to provide energy during the first phase of starvation?

Answer 27

Exogenous fuels. This is the post-prandial well-fed phase.

Question 28

What fuels are used to provide energy during the post-absorptive state (the second phase of starvation)?

Answer 28

Liver glycogen.

Question 29

What fuels are used to provide energy during the third phase of starvation?

Answer 29

Amino acids, glycerol and lactate (maintains blood glucose via gluconeogenesis).

Question 30

During which phase of starvation does the brain begin to adapt to ketone bodies as fuel to provide energy?

Answer 30

Fourth phase.

Question 31

Which organs keep producing glucose via gluconeogenesis during the fifth state of starvation?

Answer 31

The liver and kidneys.

Question 32

Which tissues are completely dependent on glucose as a source for energy?

Answer 32

Red blood cells, the brain, the lens of the eye, the medulla of the kidneys and exercising muscle.

Question 33

True or False. The brain adapts to ketone bodies in individuals with uncontrolled diabetes.

Answer 33

False. The brain does not adapt to ketone bodies to derive energy in diabetics.

Question 34

What happens to the total amount of nitrogen excreted as urea during starvation?

Answer 34

It increases during early starvation and then decreases during prolonged starvation.

Question 35

What happens to the amount of nitrogen excreted as ammonia during starvation?

Answer 35

It increases.

Question 36

Why is it beneficial that nitrogen excreted as ammonia increase during starvation?

Answer 36

It conserves important cations such as sodium and potassium.

Question 37

The excretion of nitrogen as urea increases during early starvation and then decreases as starvation continues. What is the reason for this trend?

Answer 37

The rate of gluconeogenesis from amino acids decrease during prolonged starvation.