| Question |
Answer |
| Dietary proteins are the primary source of ______ metabolized by the body. |
nitrogen |
| What catalyzes the activation of pepsin? |
H+ |
| What catalyzes the activation of trypin? |
enteropeptidase |
| What catalyzes the activation of chymotrypsin? |
trypsin |
| What catalyzes the activation of elastase? |
trypsin |
| What catalyzes the activation of carboxypeptidases? |
trypsin |
| What is the general name for digestive proteases that hydrolyze peptide bonds within the chains? |
endopeptidases |
| What are some examples of endopeptidases? |
pepsin, trypsin, chymotrypsin, elastase |
| What are the two exopeptidases? |
aminopeptidase and carboxypeptidases |
| What amino acids do pepsin cleave? |
aromatic and acidic AAs |
| What AA do trypsin cleave? |
Basic: Arg, Lys |
| What AA do chymotrypsin cleave? |
Hydrophobic: Phe, Tyr, Trp, Leu |
| What AA do elastase cleave? |
Small AAs: Ala, Gly, Ser |
| Describe trans-cellular transport mediated by secondary active transport |
Na-dependent AA transporters; Na-K ATPase pump; AA facilitated diffusion |
| In a fasting state, AA are converted mainly into what 2 AAs? |
Ala, Gln |
| What AA plays a central role in both AA synthesis and catabolism? |
Glu (Glutamate) |
| During AA synthesis, Glu donates/takes Amino N via transamination? |
donates |
| During AA catabolism, Glu donates/takes Amino N via transamination? |
takes |
| What to transamination enzymes play a role in Glutamate-AA synthesis and catabolism? |
GDH - glutamate dehydrogenase |
| PLP is derived from what nutrient? |
vitamin B6 |
| The glutamate dehydrogenase reaction uses what cofactor? |
NAD or NADP |
| Excess amino acid N is converted to what toxic substance? |
ammonia |
| Ammonia is converted to what less toxic substance at physiological pH? |
ammonium |
| What organ converts ammonia to urea? |
liver |
| What is the major nitrogenous urinary excretory product? |
urea |
| What 2 AAs require PLP as a cofactor to form NH4+? |
Serine & Threonine |
| What AAs directly contribute their N to the formation of NH4+? |
Glutamate, Glutamine, Asparagine, Serine, Threonine, Histidine |
| What AA plays a major transport role for transport of ammonia in a non-toxic form for Urea Synthesis? |
alpha-kG to Glu to Gln |
| What 2 AAs do nitrogen come from the form urea? |
Glu and Asp |
| What is CPS1? |
carbamoyl phophate sythetase 1 |
| What are the products in the urea cycle? |
ammonium, carbamoyl phosphate, citrulline, argininosuccinate, arginine, ornithine |
| What enzyme from the urea cycle is unique to the liver? |
arginase |
| What is NAG? |
N-acetyl glutamate |
| What is the role of NAG? |
formed from a build-up of ARg |
| What is the effect of fasting on urea excretion? |
increases during fasting |
| What is the ratio of Ala:glucose:urea |
2:1:1 |
Ch.18 LTI-MA 509
