CONVERSION OF AMINO ACIDS TO SPECIALIZED PRODUCTS

Question 1

The entire glycine molecule becomes atoms

Answer 1

4, 5, and 7 of purines

Question 2

The nitrogen and a-carbon of glycine are incorporated into the

Answer 2

pyrrole rings and the methylene bridge carbons of heme

Question 3

constitutes a major fraction of the free amino acids in plasma

Answer 3

Alpha alanine

Question 4

Present in coenzyme A

Answer 4

Beta alanine

Question 5

Mammalian tissues form b-alanine from

Answer 5

cytosine, carnosine, and anserine

Question 6

b-Alanine Also present as

Answer 6

b-alanyl dipeptides, principally carnosine

Question 7

activate myosin ATPase, chelate copper, and enhance copper uptake

Answer 7

carnosine and anserine (Nmethylcarnosine

Question 8

Participates in the biosynthesis of sphingosine, a component of sphingomyelin

Answer 8

Serine

Question 9

the principal source of methyl groups in the body

Answer 9

S-Adenosylmethionine

Question 10

Methionine It also contributes its carbon skeleton for the biosynthesis of the

Answer 10

3-diaminopropane portions of the polyamines spermine and spermidine

Question 11

precursor of the thioethanolamine portion of coenzyme A and of the taurine

Answer 11

L. Cysteine

Question 12

L-Cysteine is a precursor of the thioethanolamine portion of coenzyme A and of the taurine that conjugates with bile acids such as

Answer 12

Taurocholic acid

Question 13

Decarboxylation of histidine to histamine is catalyzed by a broad-specificity aromatic

Answer 13

L-amino acid decarboxylase

Question 14

catalyzes the decarboxylation of dopa, 5hydroxytryptophan, phenylalanine, tyrosine, and tryptophan

Answer 14

L-amino acid decarboxylase

Question 15

Histidine to histamine

Answer 15

Histidine decarboxylase

Question 16

formamidine donor for creatine synthesis and via ornithine to putrescine, spermine, and spermidine

Answer 16

Arginine

Question 17

The 24-hour urinary excretion of creatinine is proportionate to muscle mass and is a useful indicator of kidney function

Answer 17

Creatinine

Question 18

Glycine, arginine, and methionine participate in

Answer 18

Creatinine synthesis

Question 19

Arginine is also the precursor of the intercellular signaling molecule

Answer 19

Nitric oxide

Question 20

serves as a neurotransmitter, smooth muscle relaxant, and vasodilator

Answer 20

Nitric oxide

Question 21

function in cell proliferation and growth

Answer 21

polyamines spermidine and spermine

Question 22

Following hydroxylation of tryptophan to 5hydroxytryptophan by

Answer 22

liver tyrosine hydroxylase

Question 23

a potent vasoconstrictor and stimulator of smooth muscle contraction

Answer 23

5-hydroxytryptamine or 5-HT

Question 24

Kidney tissue, liver tissue, and fecal bacteria all convert tryptophan to ____________, then to indole ____________

Answer 24

Trytamine; 3 acetate

Question 25

Neural cells convert tyrosine to

Answer 25

Epineprine

Question 26

precursor of triiodothyronine and thyroxine

Answer 26

Tyrosine

Question 27

functions in brain tissue as an inhibitory neurotransmitter by altering transmembrane potential differences

Answer 27

g-Aminobutyrate (GABA

Question 28

It is formed by decarboxylation of Lglutamate, a reaction catalyzed by Lglutamate decarboxylase

Answer 28

g-Aminobutyrate

Question 29

an excess of ingested over excreted nitrogen, accompanies growth and pregnancy

Answer 29

Positive nitrogen balance

Question 30

where output exceeds intake, may follow surgery, advanced cancer, and kwashiorkor or marasmus

Answer 30

Negative nitrogen balance

Question 31

ammonia, derived mainly from the

Answer 31

aamino nitrogen of amino acids

Question 32

Subsequent deamination of glutamine in the liver releases ammonia, which is then converted to

Answer 32

Non toxic urea

Question 33

Each day, humans turn over ______ of their total body protein, principally muscle protein

Answer 33

1-2%

Question 34

High rates of protein degradation occur in tissues undergoing structural rearrangement such as

Answer 34

uterine tissue during pregnancy, tadpole tail tissue during metamorphosis, or skeletal muscle in starvation

Question 35

Of the liberated amino acids, approximately _____are reutilized

Answer 35

75%

Question 36

The excess nitrogen forms

Answer 36

Urea

Question 37

The susceptibility of a protein to degradation is expressed as its half-life

Answer 37

1/2

Question 38

Half-lives of liver proteins range from under

Answer 38

30 minutes - 150 hours

Question 39

Typical "housekeeping" enzymes have

Answer 39

t1/2 values of over 100 hours

Question 40

By contrast, many key regulatory enzymes have a

Answer 40

t1/2 of 0.5–2 hours

Question 41

target some proteins for rapid degradation

Answer 41

PEST proline, glutamate, serine and treonine

Question 42

The resulting peptides are then degraded to amino acids by

Answer 42

Endopeptidases

Question 43

remove amino acids sequentially from the amino and carboxyl terminals, respectively

Answer 43

Aminopeptidases and carboxypeptidases

Question 44

Extracellular, membrane-associated, and long-lived intracellular proteins are degraded in lysosomes by

Answer 44

ATP independent process

Question 45

By contrast, degradation of abnormal and other short-lived proteins occurs in the cytosol and requires

Answer 45

ATP and ubiquitin

Question 46

protein that targets many intracellular proteins for degradation

Answer 46

Ubiquitin

Question 47

Only ___of 76 residues differ between yeast and human ubiquitin

Answer 47

3

Question 48

A thioester exchange reaction transfers activated ubiquitin to

Answer 48

E2

Question 49

catalyzes transfer of ubiquitin to e -amino groups of lysyl residues of target proteins

Answer 49

E3

Question 50

Degradation occurs in a multicatalytic complex of proteases known as the

Answer 50

Proteasome

Question 51

responsible for degrading proteins are in the stomach, pancreas, and small intestine

Answer 51

Proteolytic enzyme

Question 52

Pancreatic proteases further cleave ___________initially digested by the stomach

Answer 52

Polypeptides

Question 53

Enteropeptidase from the intestine activates pancreatic enzymes such as ___________ to its active form

Answer 53

Trypsinogen

Question 54

SMALL INTESTINE •Contains ____________that cleaves oligopeptides to produce free amino acids

Answer 54

Aminopeptidase

Question 55

further hydrolyzed in the cytosol before being released to the portal system

Answer 55

Dipeptides

Question 56

ammonotelic

Answer 56

Excrete ammnonia fish

Question 57

which must conserve water and maintain low weight, are uricotelic and excrete uric acid as semisolid guano

Answer 57

Birds

Question 58

Many land animals, including humans, are ________ and excrete nontoxic, water-soluble urea

Answer 58

Ureotelic

Question 59

Urea biosynthesis occurs in 4 stages

Answer 59

transamination (2) oxidative deamination of glutamate (3) ammonia transport (4) reactions of the urea cycle

Question 60

Transamination interconverts pairs of

Answer 60

a-amino acids and a-keto acids

Question 61

participate in transamination except

Answer 61

lysine, threonine, proline, and hydroxyproline

Question 62

present at the catalytic site of aminotransferases and of many other enzymes that act on amino acids

Answer 62

Pyridoxal phosphate

Question 63

During transamination, bound PLP serves as a

Answer 63

Carrier of amino acids

Question 64

removal of a-amino nitrogen by transamination, the remaining carbon "skeleton" is

Answer 64

Degraded

Question 65

These 2 enzymes catalyze the transfer of amino groups to pyruvate (forming alanine) or to aketoglutarate (forming glutamate

Answer 65

Alanine amino transferase ang glutamate amino transferase

Question 66

Since alanine is also a substrate for glutamate aminotransferase, all the amino nitrogen from amino acids that undergo transamination can be concentrated in

Answer 66

Glutamate

Question 67

the only amino acid that undergoes oxidative deamination at an appreciable rate in mammalian tissues

Answer 67

L glutamate

Question 68

The formation of ammonia from a-amino groups thus occurs mainly via the

Answer 68

a -amino nitrogen of L-glutamate

Question 69

Transfer of amino nitrogen to a-ketoglutarate forms

Answer 69

L glutamate

Question 70

Release of this nitrogen as ammonia is then catalyzed by hepatic L-glutamate dehydrogenase (GDH), which can use either NAD+ or NADP+

Answer 70

L glutamate dehyrogenase GH

Question 71

Conversion of a-amino nitrogen to ammonia by the concerted action of glutamate aminotransferase and GDH is often termed

Answer 71

Transdeamination

Question 72

allosterically inhibited by ATP, GTP, and NADH and activated by ADP

Answer 72

Liver GDH activity

Question 73

The reaction catalyzed by GDH is freely reversible and functions also in

Answer 73

Amino acid synthesis

Question 74

Ammonia may be toxic to the brain in part because it reacts with

Answer 74

a-ketoglutarate to form glutamate

Question 75

The urea cycle consists of

Answer 75

five reactions - two mitochondrial and three cytosolic

Question 76

the carrier of these carbon and nitrogen atoms

Answer 76

Ornithine

Question 77

functions as an enzyme activator

Answer 77

N-acetylglutamate

Question 78

This is the rate-limiting enzyme of the urea cycle

Answer 78

Carbamoyl Phosphate Synthase I

Question 79

rate-limiting enzyme of the urea cycle •This enzyme is active only in the presence of its allosteric activator

Answer 79

N-acetylglutamate

Question 80

Formation of carbamoyl phosphate requires

Answer 80

2 mol of atp

Question 81

catalyzes transfer of the carbamoyl group of carbamoyl phosphate to ornithine, forming citrulline and orthophosphate

Answer 81

L-Ornithine transcarbamoylase

Question 82

autosomal recessive defect in the gene for arginase

Answer 82

Hyperargininemia