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27 Cards in this Set

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Where does the degradation of ingested proteins occur?
In the gastrointestinal tract?
Pepsinogen is converted to what, and in what type of fluid (juice)?
Pepsinogen is converted to active pepsin in gastric juice by the autocatalysis of pepsin itself.
What types of bonds/proteins does pepsin hydrolyze?
Pepsin hydrolyzes those peptide bonds of ingested proteins involving the aromatic amino acids (tyrosine, phenylalanine, tryptophan) among others.
What enzyme converts trysinogen to trypsin? What is the characteristic of the proteins hydrolyzed by trypsin?
Enteropeptidate converts trypsinogen to trypsin. Free trypsin hydrolyzes those peptide bonds whose carbonyl groups are contributed by lysin and arginine residues in the small intestine.
How is chymotrypsinogen converted to chymotrypsin? What types of bonds does it hydrolyze?
Chymotrypsinogen is converted to chymotrypsin by trypsin. It hydrolyzes those peptide bonds involving phenylalanine, tryptophan, and tyrosine.
Inactive zymogen procarboxypeptidase is converted to ? and removes ?.
carboxypeptidase; successive carboxyl-terminal residues
Aminopeptidase hydrolyzes what?
Amino-terminal residues from short peptides
What do parietal cells secrete?
HCl
What do chief cells secrete?
Pepsinogen
What does the gastric mucosa secrete?
Gastrin. The parietal cells and chief cells of the gastric glands secrete their products in response to the hormone gastrin.
What is the function of transaminases/aminotransferase?
They promote the removal of the α-amino groups of most of the L-amino acids. These reactions are called transanimations.
What reaction does alanine transaminase catalyze?
The transfer of an amino group to pyruvate.
What is the function of aspartate transaminase?
catalyzes an amino group of L-aspartate to oxaloacetate.

It converts L-aspartate to oxaloacetate.
Which six amino acids are degraded to pyruvate?
serine, glycine, alanine, threonine, tryptophan, cysteine
Which two amino acids can be directly deaminated and why?
Serine and threonine can be directly deaminated because each of these amino acids contains a hydroxyl group in its side chain.
Which enzymes catalyze the direct deamination of serine and threonine?
Serine dehydratase and threonine dehydratase.
What does leucine transaminase catalyze?
An amino group from L-leucine to α-ketoisocaproate.
What does tyrosine transaminase catalyze?
Tyrosine transaminase catalyzes an amino group of L-tyrosine to p-hydroxyphenylpyruvate.
What is threonine deaminated to?
α-ketobutyrate
After removal of their amino groups, what is the fate of the carbon skeletons?
The carbon skeletons of amino acis undergo oxidation to compounds that can enter the citric acid cycle for oxidation to CO2 and H2O.
Which six amino acids are degraded to pyruvate?
serine, glycine, alanine, tryptophan, threonine, cysteine
Which seven amino acids are degraded to acetyl-CoA
threonine, isoleucine, leucine, tryptophan, phenylalanine, lysine, tyrosine
_______ breakdown is the most complex of all the pathways of amino acid catabolism in animal tissues.
Tryptophan
Amino acid catabolism to acetyl-CoA leads to ? in humans.
Succinyl-CoA
Which five amino acids are converted to α-ketoglutarate?
proline, glutamate, arginine, glutamine, histidine
Which four amino acis are converted to succinyl-CoA?
methionine, isoleucine, valine, threonine
Which amino acids are degraded by oxygenases? Describe the steps
Phenylalanine and tyrosine are degraded by oxygenases. The first step is the hydroxylation of phenylalaine to tyrosine via phenylalaine hydroxylase.

Phenylalaline to tyrosine to p-hydroxyphenylpyruvate to homogentisate