MCP - Turner - Metabolic Integration -2/27

Question 1

What amino acids are both glucogenic and ketogenic?

Answer 1

Isoleucine
Phenylalanine
Tyrosine
Tryptophan

Question 2

T/F: We can make glucose from fatty acids by running the citric acid cycle.

Answer 2

FALSE. FA are broken down to acetyl-CoA. If you run the whole CAC, and end up with OAA, that can be converted back to glucose, but there is no “net” conversion of FA to glucose.

Exception to this rule: Odd-chain FAs are broken down partly into propionyl-CoA, which can be converted to glucose

Question 3

Glucogenic amino acids produce what element of the TCA cycle?

Answer 3

Pyruvate

Question 4

Ketogenic amino acids produce what element of the TCA cycle?

Answer 4

Acetyl-CoA

Question 5

Choose the correct answer:

Enzymes involved in catabolism and energy mobilization are active when PHOSPHORYLATED / DEPHOSPHORYLATED.

Answer 5

Phosphorylated, ie:
Glycogen phosphorylase
phosphorylase kinase
hormone-sensitive lipase

Question 6

When are anabolic enzymes inactive?

Answer 6

When they are phosphorylated, ie:
acetyl-CoA carboxylase
glycogen synthase
HMG-CoA reductase

Insulin promotes dephosphorylation of anabolic enzymes to activate them

Question 7

What is the role of HMG-CoA reductase?

Answer 7

It’s an enzyme involved in cholesterol synthesis, activated by insulin and inactivated by glucagon

Question 8

Glucagon stimulates elevated levels of cAMP which lead to activation of what transcription factor, which produces PEPCK?

Answer 8

CREB

Increased PEPCK results in some TG resynthesis (circling of fat breakdown and synthesis in response to the same hormone…thought to contribute to thermoregulation, and to protect the body from wasting NEFA stores too quickly)

Question 9

What is considered the major gluconeogenic amino acid?

Answer 9

alanine

Question 10

Give 5 metabolic changes during prolonged fasting:

Answer 10

1. Muscle - less utilization of KBs
2. Brain - increased utilization of KB
3. Liver - less gluconeogenesis
4. Muscle - less protein degradation
5. Liver - less production of urea

Question 11

What is ketoacidosis?

Answer 11

When KB production overwhelms KB removal, and KBs are thus present in the bloodstream
ie diabetes type I

Question 12

Does ketoacidosis occur in starvation?

Answer 12

No, KBs are used by various tissues, ie the brain, or excreted by the kidneys

Question 13

What is the difference between the actions of epinephrine and glucocorticoids in the liver?

Answer 13

Glucocorticoids stimulate the synthesis of glycogen in the liver, whereas epi stimulates glycogen breakdown in the liver.
Both stimulate gluconeogenesis in the liver.

Question 14

What is aerobic glycolysis?

Answer 14

An energy pathway alternative in cancer cells.

Cancer cells take up a lot of glucose, convert it to pyruvate, but do not feed it into the TCA cycle. Instead they convert the pyruvate to lactate, which is then secreted.

The pentose phosphate pathway is very active in cancer cells, making NADPH and ribose-5-phosphate for biosynthesis and cell division.

Cancer cells also take up a lot of glutamine, which is converted to glutamate in the mitochondria, also for biosynthesis.

Inactivation of the tumor suppressor gene p53 leads to activation of these aerobic glycolytic behaviors.