Amino Acid Metabolism

Question 1

Amino acids can be classified as

Answer 1

glucogenic & ketogenic

Question 2

Amino acids whose catabolism yields

Answer 2

pyruvate

Question 3

Amino acids whose catabolism yields pyruvate or one of the intermediates of the citric acid cycle are termed

Answer 3

glucogenic

Question 4

Only exclusively found in proteins like leucine and lysine, which are not substrates for gluconeogenesis, preventing glucose formation.

Answer 4

Ketogenic amino acids

Question 5

Asparagine hydrolyzed by

Answer 5

asparaginase

Question 6

loses its amino group by transamination to form oxaloacetate.

Answer 6

Aspartate

Question 7

can be administered systemically to treat leukemic patients, as it lowers asparagine levels in the plasma, depriving cancer cells of a required nutrient.

Answer 7

Asparaginase

Question 8

This amino acid is converted to glutamate and ammonia by the enzyme glutaminase

Answer 8

Glutamine

Question 9

Glutamine: This amino acid is converted to glutamate and ammonia by the enzyme?

Answer 9

glutaminase

Question 10

Glutamate is converted to α-keto glutarate by transamination, or through oxidative deamination by?

Answer 10

glutamate dehydrogenase

Question 11

This amino acid is oxidized to glutamate. Glutamate is transaminated or oxidatively deaminated to form α-ketoglutarate.

Answer 11

Proline

Question 12

This amino acid is cleaved by arginase to produce ornithine

Answer 12

Arginine

Question 13

This amino acid is oxidatively deaminated by histidase to urocanic acid, which subsequently forms N-formimino glutamate (FIGlu).

Answer 13

Histidine

Question 14

Histidine: This amino acid is oxidatively deaminated by histidase to urocanic acid, which subsequently forms?

Answer 14

N-formimino glutamate (FIGlu)

Question 15

Amino acids that form α-ketoglutarate via glutamate

Answer 15

1. Glutamine
2. Proline
3. Arginine
4. Histidine

Question 16

Amino acids that form pyruvate;

Answer 16

1. Alinine
2. Serine
3. Glycine
4. Cystine
5. Threonine

Question 17

The major gluconeogenic amino acid. This amino acid loses its amino group by reversible transamination to form pyruvate.

Answer 17

Alanine

Question 18

An amino acid can be converted to glycine and N^5, N^10 methylenetetra hydrofolate

Answer 18

Serine

Question 19

Serine can be converted to glycine and N^5, N^10 methylenetetra hydrofolate. It can also be converted to pyruvate by?

Answer 19

serine dehydratase

Question 20

This amino acid can be converted to serine by the reversible addition of a methylene group from N^5, N^10-methylenetetrahydrofolic acid or oxidized to CO2 and NH3.

Answer 20

Glycine

Question 21

Glycine can be converted to?

Answer 21

glyoxylate

Question 22

This amino acid is reduced to cysteine, using NADH + H^+ as a reductant.

Answer 22

Cystine

Question 23

Cysteine undergoes desulfuration to yield?

Answer 23

pyruvate

Question 24

This amino acid is converted to pyruvate or to α-ketobutyrate, which forms succinyl CoA.

Answer 24

Threonine

Question 25

Amino acids that form fumarate:

Answer 25

1. Phenylalanine and tyrosine 2. Inherited deficiencies

Question 26

Hydroxylation of phenylalanine produces?

Answer 26

tyrosine

Question 27

in the enzymes of phenylalanine and tyrosine metabolism lead to the diseases phenylketonuria and alkaptonuria, and the condition of albinism.

Answer 27

Inherited deficiencies

Question 28

Amino acids that form succinyl CoA:

Answer 28

methionine

Question 29

is one of four amino acids that form succinyl CoA.

Answer 29

Methionine

Question 30

This sulfur-containing amino acid deserves special attention because it is converted to S-adenosyl methionine (SAM), the major methyl-group donor in one-carbon metabolism.

Answer 30

Methionine

Question 31

Methionine is also the source of?

Answer 31

homocysteine

Question 32

a metabolite associated with atherosclerotic vascular disease.

Answer 32

homocysteine

Question 33

a high-energy compound that is unusual in that it contains no phosphate.

Answer 33

SAM

Question 34

is hydrolyzed to homocysteine and adenosine

Answer 34

SAH

Question 35

accepts a methyl group from N5-methyltetrahydrofolate (N5-methyl-THF) requiring methylcobalamin.

Answer 35

Homocysteine

Question 36

Homocysteine condenses with

Answer 36

serine

Question 37

These amino acids are branched-chain amino acids that generate propionyl CoA, which is converted to succinyl CoA by biotin- and vitamin B12–requiring reactions

Answer 37

Valine and isoleucine

Question 38

This amino acid is dehydrated to α-ketobutyrate, which is converted to propionyl CoA and then to succinyl CoA.

Answer 38

Threonine

Question 39

Amino acids that form acetyl CoA or acetoacetyl CoA:

Answer 39

1. Leucine 2. Isoleucine 3. Lysine 4. Trytophan

Question 40

This amino acid is exclusively ketogenic in its catabolism, forming acetyl CoA and acetoacetate.

Answer 40

Leucine

Question 41

This amino acid is both ketogenic and glucogenic, because its metabolism yields acetyl CoA and propionyl CoA.

Answer 41

Isoleucine

Question 42

An exclusively ketogenic amino acid, this amino acid is unusual in that neither of its amino groups undergoes transamination as the first step in catabolism.

Answer 42

Lysine

Question 43

This amino acid is both glucogenic and ketogenic because its metabolism yields alanine and acetoacetyl CoA.

Answer 43

Tryptophan

Question 44

Removal of the amino groups of all three amino acids is catalyzed by a single, vitamin B6–requiring enzyme, branched-chain amino acid aminotransferase.

Answer 44

Transamination

Question 45

Removal of the carboxyl group of the α-keto acids derived from leucine, valine, and isoleucine is catalyzed by a single multienzyme complex, branched-chain α-keto acid dehydrogenase complex.

Answer 45

Oxidative decarboxylation

Question 46

Oxidation of the products formed in the above reaction yields α-β-unsaturated acyl CoA derivatives.

Answer 46

Dehydrogenation

Question 47

a carrier of one-carbon units

Answer 47

Folic acid

Question 48

is produced from folate by dihydrofolate reductase in a two-step reaction requiring two NADPH.

Answer 48

tetrahydrofolic acid (THF)

Question 49

allows one-carbon compounds to be recognized and manipulated by biosynthetic enzymes.

Answer 49

tetrahydrofolic acid (THF),

Question 50

Most important disease of amino acid metabolism because it is relatively common and responds to dietary treatment. This is caused by a deficiency of phenylalanine hydroxylase. It is a common inborn amino acid metabolism error, characterized by phenylalanine accumulation and tyrosine deficiency.

Answer 50

Phenylketonuria (PKU)

Question 51

may also caused by enzyme deficiencies required to synthesize BH4, or in dihydropteridine reductase, which regenerates BH4 from BH2.

Answer 51

Hyperphenylalaninemia

Question 52

Characteristics of classic PKU:

Answer 52

1. Elevated phenylalanine 2. CNS symptoms 3. Hypopigmentation

Question 53

is present in elevated concentrations in tissues, plasma, and urine.

Answer 53

Phenylalanine

Question 54

Mental retardation, failure to walk or talk, seizures, hyperactivity, tremor, microcephaly, and failure to grow are characteristic findings in

Answer 54

Phenylketonuria

Question 55

The hydroxylation of tyrosine by tyrosinase, which is the first step in the formation of the pigment melanin, is competitively inhibited by the high levels of phenylalanine present in?

Answer 55

Phenylketonuria

Question 56

is a treatable disease that requires early diagnosis due to its treatable nature

Answer 56

Phenylketonuria

Question 57

is a family of diseases caused by over 100 mutations in the phenylalanine hydroxylase (PAH) gene, with frequency varying among populations and often doubly heterozygous

Answer 57

Classic PKU

Question 58

is an essential amino acid and a key component of most natural proteins.

Answer 58

Phenylalanine

Question 59

When a woman with PKU who is not on a low-phenylalanine diet becomes pregnant, the offspring will be affected with?

Answer 59

maternal PKU syndrome

Question 60

is a rare autosomal recessive disorder characterized by a partial or complete deficiency in branched-chain α-keto acid dehydrogenase, an enzyme complex that decarboxylates amino acids.

Answer 60

Maple syrup urine disease (MSUD)

Question 61

is a disorder with a classic type and several variant forms.

Answer 61

Maple syrup urine disease (MSUD)

Question 62

- Defect in tyrosine metabolism leads to melanin production deficiency. - Causes partial or full absence of pigment from skin, hair, and eyes.

Answer 62

Albinism

Question 63

also known as tyrosinase-negative oculocutaneous albinism, results from copper-requiring tyrosinase deficiency.

Answer 63

Complete albinism

Question 64

are inherited as autosomal recessive illnesses caused by a defect in the enzyme cystathionine β-synthase

Answer 64

Homocystinurias

Question 65

• A Rare Metabolic Condition • Deficiency in homogentisic acid oxidase leads to accumulation of homogeneic acid. • Symptoms include homogentisic aciduria, large joint arthritis, and black ochronotic pigmentation of cartilage and collagenous tissue. • Usually asymptomatic until age 40, with occasional diaper staining.

Answer 65

Alkaptonuria