Protein Metabolism

Question 1

results when a child is weaned onto a starchy diet poor in protein

Answer 1

kwashiorkor

Question 2

both caloric intake and specific amino acids are deficient.

Answer 2

marasmus

Question 3

conformational instability of collagen results in

Answer 3

bleeding gums, swelling joints, poor wound healing, and ulti-mately in death.

Question 4

an essential cofactor for the enzyme lysyl oxidase that functions in formation of the covalent cross-links

Answer 4

copper

Question 5

dependence on an external supply of a given nutrient can be of greater survival value than the ability to biosynthesize it
True or False

Answer 5

True

Question 6

allows release of the product, glutamine.

Answer 6

Release of Pi and of a proton from the γ-amino group of the tetrahedral intermediate

Following the ordered binding of glutamate and ATP, glutamate attacks the γ-phosphorus of ATP, forming γ-glutamyl phosphate and ADP. NH4+ then binds, and uncharged NH3 attacks γ-glutamyl phosphate

Question 7

Transamination of pyruvate forms

Answer 7

alanine

Question 8

transamination of oxaloacetate forms

Answer 8

aspartate

Question 9

nutritionally Essential

Answer 9

AHILLMPTTV

Argininea histidine Isoleucine Leucine Lysine

Methionine phenylalanine Threonine Tryptophan Valine

Question 10

converts inorganic ammonium ion into the α-amino nitrogen of amino acids.

Answer 10

combined action of the enzymes glutamate dehydro-genase, glutamine synthetase, and the aminotransferases

Question 11

catalyze the synthesis of glycine from glyoxylate and glutamate or alanine.

Answer 11

Glycine aminotransferases

Question 12

Additional important mammalian routes for glycine formation are from

Answer 12

choline and serine

Question 13

The initial reaction of proline biosynthesis

Answer 13

converts the γ-carboxyl group of glutamate to the mixed acid anhydride of glutamate γ-phosphate

Subsequent reduction forms glutamate γ-semialdehyde, which following spontaneous cyclization is reduced to l-proline

Question 14

whose hydrolysis forms cysteine and homoserine

Answer 14

cystathionine

Question 15

since the phenylalanine hydroxylase reaction is reversible, dietary tyrosine cannot replace phenylalanine.
True or False

Answer 15

False. Irreversible

Question 16

Hydroxylation of peptidyl prolyl and pep-tidyl lysyl residues, catalyzed by _____________ and ____________ of skin, skeletal muscle, and granulating wounds requires, in addition to the substrate, molecular O2, ascorbate, Fe2+, and α-ketoglutarate

Answer 16

prolyl hydroxylase and lysyl hydroxylase

Question 17

Selenocysteine is present at the active site of several human enzymes that catalyze redox reactions.

Answer 17

Examples include thioredoxin reductase, glutathione peroxidase, and the deiodinase that converts thyroxine to triiodothyronine

Question 18

selenium deficiency cardiomyopathy

Answer 18

Keshan disease

Question 19

The ability of the protein synthetic apparatus to identify a selenocysteinespecific UGA codon involves

Answer 19

the selenocysteine insertion element, a stem-loop structure in the untranslated region of the mRNA

Question 20

The intermediates and the amino acids to which they give rise are

Answer 20

α-ketoglutarate (Glu, Gln, Pro, Hyp), oxaloacetate (Asp, Asn), and 3-phosphoglycerate (Ser, Gly).

Question 21

are formed from nutritionally essential amino acids.

Answer 21

Cysteine, tyrosine, and hydroxylysine

Question 22

an essential active site residue in several mammalian enzymes, arises by cotranslational insertion from a previously modified tRNA.

Answer 22

Selenocysteine