Nitrogen Economy 1

Question 1

What does nitrogen enter the body as? (AAs / fats / carbs)

Answer 1

Mostly as amino acids in dietary protein!

Question 2

Gluconeogenesis is fueled by 3 raw materials. What are they?

Answer 2

• glycerol (from lipolysis)
• lactate (from anaerobic metabolism)
• amino acids (alanine)

Question 3

Degradation of proteins is determined by _____.

Answer 3

The half-life of proteins

Question 4

P, E, S, T significance. regarding half-lives?

Answer 4

Proline, Glutamate, Serine and Threonine all have SHORT half-lives

Question 5

Characteristics of Parietal cells

Answer 5

• Produce HCl, keeping stomach pH below 1

- Contain carbonic anhydrase

Question 6

Role of secretin?

Answer 6

• Stimulates pancreatic bicarbonate secretion, which neutralizes gastric HCl

Question 7

I cells secrete ____ which use (Gs/Gq) to activate IP3 and DAG to release enzymes

Answer 7

CCK, Gq

Question 8

S cells secrete ____ which use (Gs/Gq) to activate CAMP

Answer 8

Secretin, Gs

Question 9

Transport of amino acids into cells?

Answer 9

Secondary transport; Na+ linked co-transport. Very high oxygen demand is seen.

Question 10

In Cystinuria, the apical transport system, ____, mediates influx of amino acids and ____

Answer 10

B-zero +, CSSC

Question 11

If the B-zero + transporter is defective, what results?

Answer 11

Cystinuria, because of the accumulation and thus, precipitation, of CSSC. (kidney stones)

Question 12

In cystinuria, which amino acid must be restricted, as a diet?

Answer 12

Methionine, bc it can break down and form cystine.

Question 13

Cystinosis

Answer 13

• Cystine accumulates in the lysosomes and cannot be exported out to the cytosol

Question 14

Hartnup disease

Answer 14

• Due to amino acid transporter deficiency (failing to absorb tryptophan)
• Pellagra-like sx are seen

Question 15

With Hartnup dx, if Trp cannot be absorbed: what, then, cannot occur as a product?

Answer 15

Niacin! In Hartnup dx, niacin will be deficient bc there is no Trp to process into niacin

Question 16

In patients with Niacin deficiency, what do they develop?

Answer 16

Pellagra (4 Ds: diarrhea, dermatitis, dementia, death)

Question 17

Where is urea produced? Where is ammonia produced?

Answer 17

Urea is produced in the liver, and ammonia is produced in the kidney

Question 18

In which state (fed/fasting) is the most urea produced?

Answer 18

During the first day or so, of the fasting period

Question 19

Which “long term stress hormone” initiates the degradation of body protein?

Answer 19

Cortisol - it supports gluconeogenesis in the fasting state, thereby accelerating nitrogen loss

Question 20

During a fasting state, as proteins are being degraded for fuel, which are the main two AAs?

Answer 20

Alanine and Glutamine

• Both go to the liver (used in gluconeogenesis).
• The nitrogen is disposed as urea

Question 21

Exercise increases activity of the purine nucleotide cycle, which converts _____ to _____ plus ammonia

Answer 21

Converts aspartate to fumarate

An increase in the amount of fumarate increases the capacity of the TCA cycle