Nitrogen and Urea

Question 1

what are zymogens, and what are four different kings

Answer 1

become active enzymes in dietary protein digestion

Question 2

what is low HCl concentration called and what can it cause?

Answer 2

achlorhydria and it can cause iron deficiency

Question 3

pancreatic zymogens

Answer 3

(activated by proteolysis)

1. trypsinogen > trypsin (by enteropeptidase)
2. chymotrypsinogen > chymotrypsin (by trypsin)
3. proelastase > elastase (by trypsin)
4. procarboxypeptidases > carboxypeptidase A or B –exopeptidase (by tripsin)

Question 4

which endopeptide amino acids does trypsin cleave?

Answer 4

lysines and arginines

Question 5

defects in neutral amino acid transport system lead to what, and what is the main source of their symptoms

Answer 5

Hartnup disease–(neutral amidoaciduria) ataxia, emotional instability, pellagra rash)

tryptophan deficiency here is precursor for niacin (B3), and deficiency in niacin responsible for most of the symptoms

Question 6

where does proteolysis occur intracellularly

Answer 6

in lysosomes (with acid hydrolases, pH of 5 optimal)
in cytosol (poly-ubiquitin-tagged proteins degraded by 26S proteasome)

Question 7

2 types of extracellular proteolyses

Answer 7

serine proteases and matrix metalloproteases (collagenases)

Question 8

what protease problem occurs in chronic pulmonary disease

Answer 8

elastase (a serine protease) from neutrophils contributes to lung damage

Question 9

where do nitrogens come from in urea

Answer 9

nitrogen from amino acids goes to aspartate and ammonia which combine in urea cycle (with CO2) to form urea

Question 10

acute encephalopathy is associated with

Answer 10

hyperammonemia (high ammonium concentration which is very toxic to the nervous system)

Question 11

aminotransferase catalyze transfer of alpha-amino group from amino acid to alpha-ketoacid with use of what?

Answer 11

pyridoxal phosphate (PLP) from pyridoxine or Vitamin B6–can have too much

note: aldehyde carbon forms schiff base (C=N)

Question 12

what are used to evaluate liver damage (especially from solvents)

Answer 12

serum alanine aminotransferase (ALT) and asparate aminotransferase (AST)

Question 13

what occurs in oxidative deamination and where is it located

Answer 13

glutamate dehydrogenase cleaves nitrogen from glutamate to produce alpha-ketoglutarate and ammonium ion (can use NADH or NADPH).
occurs in the liver under when energy low

Question 14

hydrolytic deamination reduces side chains of what two amide groups

Answer 14

asparagine and glutamine (contain amides)

Question 15

which two amino acids use nonoxidative deamination and what is this method dependent on

Answer 15

serine (serine dehydratase) and threonine (theonine dehydratase). dehydration precedes deamination, and both use PLP prosthetic group

Question 16

how is nitrogen transported from muscle to liver

Answer 16

glutamine and alanine transport in blood. glutamine deaminated to glutamate and deaminated again to alpha-ketoglutarate

Question 17

glutamine synthase

Answer 17

can fix ammonium ion in carbon compound and converts glutamate to glutamine with ATP

Question 18

4 things oxaloacetate can turn into

Answer 18

1. transamination to aspartate
2. conversion to glucose
3. condensation with acetyl coA to form citrate
4. conversion into pyruvateq

Question 19

high levels of glutamine in brain cause

Answer 19

osmotic increase in H2O in astroytes and get brain swelling. incr. glutamine causes decrease in neurotransmitters glutamate and GABA

Question 20

shift of equilibrium of glutamate dehydrogenase may cause

Answer 20

depleted alpha-ketoglutarate (essential for TCA) resulting in decr oxidation and ATP
(hyperammonemia particularly bad for brain because depends on TCA for energy)

Question 21

treatment for defects in urea cycle

Answer 21

hemodialysis/transfusion (for acute)
limit protein in diet, high carb
remove excess ammonia (take levulose, avoid infections, kill intestinal ammonia w/ antibiotics. benzoate to reduce glutamine
replace intermediates (supp with arginine or citrulline)

Question 22

circumventing ways to remove urea

Answer 22

glycine removed by benzoic acid and glutamine removed by phenybutyrate

Question 23

ornithine transcarbamylase deficiency

Answer 23

x-linked trait causes hyperammonemia and in male infants, explosive neonatal hyperammonemia

what Jesse Gelsinger had