Amino Acid Metabolism

Front 1

Where does the degradation of ingested proteins occur?

Back 1

In the gastrointestinal tract?

Front 2

Pepsinogen is converted to what, and in what type of fluid (juice)?

Back 2

Pepsinogen is converted to active pepsin in gastric juice by the autocatalysis of pepsin itself.

Front 3

What types of bonds/proteins does pepsin hydrolyze?

Back 3

Pepsin hydrolyzes those peptide bonds of ingested proteins involving the aromatic amino acids (tyrosine, phenylalanine, tryptophan) among others.

Front 4

What enzyme converts trysinogen to trypsin? What is the characteristic of the proteins hydrolyzed by trypsin?

Back 4

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.

Front 5

How is chymotrypsinogen converted to chymotrypsin? What types of bonds does it hydrolyze?

Back 5

Chymotrypsinogen is converted to chymotrypsin by trypsin. It hydrolyzes those peptide bonds involving phenylalanine, tryptophan, and tyrosine.

Front 6

Inactive zymogen procarboxypeptidase is converted to ? and removes ?.

Back 6

carboxypeptidase; successive carboxyl-terminal residues

Front 7

Aminopeptidase hydrolyzes what?

Back 7

Amino-terminal residues from short peptides

Front 8

What do parietal cells secrete?

Back 8

HCl

Front 9

What do chief cells secrete?

Back 9

Pepsinogen

Front 10

What does the gastric mucosa secrete?

Back 10

Gastrin. The parietal cells and chief cells of the gastric glands secrete their products in response to the hormone gastrin.

Front 11

What is the function of transaminases/aminotransferase?

Back 11

They promote the removal of the α-amino groups of most of the L-amino acids. These reactions are called transanimations.

Front 12

What reaction does alanine transaminase catalyze?

Back 12

The transfer of an amino group to pyruvate.

Front 13

What is the function of aspartate transaminase?

Back 13

catalyzes an amino group of L-aspartate to oxaloacetate.

It converts L-aspartate to oxaloacetate.

Front 14

Which six amino acids are degraded to pyruvate?

Back 14

serine, glycine, alanine, threonine, tryptophan, cysteine

Front 15

Which two amino acids can be directly deaminated and why?

Back 15

Serine and threonine can be directly deaminated because each of these amino acids contains a hydroxyl group in its side chain.

Front 16

Which enzymes catalyze the direct deamination of serine and threonine?

Back 16

Serine dehydratase and threonine dehydratase.

Front 17

What does leucine transaminase catalyze?

Back 17

An amino group from L-leucine to α-ketoisocaproate.

Front 18

What does tyrosine transaminase catalyze?

Back 18

Tyrosine transaminase catalyzes an amino group of L-tyrosine to p-hydroxyphenylpyruvate.

Front 19

What is threonine deaminated to?

Back 19

α-ketobutyrate

Front 20

After removal of their amino groups, what is the fate of the carbon skeletons?

Back 20

The carbon skeletons of amino acis undergo oxidation to compounds that can enter the citric acid cycle for oxidation to CO2 and H2O.

Front 21

Which six amino acids are degraded to pyruvate?

Back 21

serine, glycine, alanine, tryptophan, threonine, cysteine

Front 22

Which seven amino acids are degraded to acetyl-CoA

Back 22

threonine, isoleucine, leucine, tryptophan, phenylalanine, lysine, tyrosine

Front 23

_______ breakdown is the most complex of all the pathways of amino acid catabolism in animal tissues.

Back 23

Tryptophan

Front 24

Amino acid catabolism to acetyl-CoA leads to ? in humans.

Back 24

Succinyl-CoA

Front 25

Which five amino acids are converted to α-ketoglutarate?

Back 25

proline, glutamate, arginine, glutamine, histidine

Front 26

Which four amino acis are converted to succinyl-CoA?

Back 26

methionine, isoleucine, valine, threonine

Front 27

Which amino acids are degraded by oxygenases? Describe the steps

Back 27

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