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biochem 2 > protein p2 > Flashcards

protein p2 Flashcards

1
Q

Which bond can PLP enzymes break in the amino acid substrate?
a) Cα-Hα bond (aminotransferases)
b) Cα-CO bond (decarboxylases)
c) Cα-Cβ bond (aldolases)

A

b) Cα-CO bond (decarboxylases)

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2
Q

What are the common characteristics exhibited by PLP enzymes?
a) Formation of disulfide bonds
b) Formation of peptide bonds
c) Schiff base formation
d) Formation of hydrogen bonds

A

c) Schiff base formation

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3
Q

In what role does the protonated form of PLP act during enzymatic reactions?
a) As a reducing agent
b) As an oxidizing agent
c) As a nucleophilic catalyst
d) As an electrophilic catalyst

A

d) As an electrophilic catalyst

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4
Q

How is the product Schiff base formed by PLP enzymes typically handled at the end of the reaction?
a) It remains bound to the enzyme indefinitely
b) It is released into the surrounding medium
c) It is cleaved from the enzyme
d) It undergoes spontaneous degradation

A

c) It is cleaved from the enzyme

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5
Q

In aminotransferases, which bond is typically positioned perpendicular to the pyridine ring of PLP for cleavage?
a) Cα-CO bond
b) Cα-Hα bond
c) Cα-Cβ bond
d) Cα-N bond

A

b) Cα-Hα bond

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6
Q

Which enzyme converts serine to glycine by cleaving a specific bond perpendicular to the pyridine ring of PLP?
a) Glutamate decarboxylase
b) Serine hydroxymethyltransferase
c) Aspartate aminotransferase
d) Pyruvate carboxylase

A

b) Serine hydroxymethyltransferase

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7
Q

Which bond is typically oriented perpendicular to the π-cloud in aminotransferases?
a) Cα-CO bond
b) Cα-Hα bond
c) Cα-Cβ bond
d) Cα-N bond

A

b) Cα-Hα bond

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8
Q

How do PLP enzymes ensure the correct orientation of the bond for cleavage?
a) Through allosteric regulation
b) By forming a covalent bond with the substrate
c) By evolving to position the bond correctly
d) Through the action of chaperone proteins

A

c) By evolving to position the bond correctly

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9
Q

Elevated blood levels of alanine and aspartate aminotransferases are indicative of:
a) Kidney damage
b) Brain injury
c) Liver damage
d) Lung disease

A

c) Liver damage

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10
Q

What are the common causes of liver damage leading to increased blood levels of aminotransferases?
a) Bacterial infections
b) Viral hepatitis, excessive alcohol consumption, and drug reactions
c) Allergic reactions to food
d) Genetic disorders

A

b) Viral hepatitis, excessive alcohol consumption, and drug reactions

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11
Q

How do aminotransferases enter the bloodstream in cases of liver damage?
a) Through active secretion by liver cells
b) Diffusion from surrounding tissues
c) Leakage from damaged liver cell membranes
d) Synthesis in the blood vessels

A

c) Leakage from damaged liver cell membranes

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12
Q

What is the diagnostic significance of measuring blood levels of aminotransferases?
a) Indicating kidney function
b) Assessing heart health
c) Monitoring lung capacity
d) Detecting liver damage

A

d) Detecting liver damage

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13
Q

Which enzymes catalyze the direct deamination of serine and threonine?
a) Serine transaminase and threonine transaminase
b) Serine dehydrogenase and threonine dehydrogenase
c) Serine dehydratase and threonine dehydratase
d) Serine decarboxylase and threonine decarboxylase

A

c) Serine dehydratase and threonine dehydratase

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14
Q

What is the initial step in the deamination of serine and threonine?
a) Dehydration
b) Transamination
c) Hydroxylation
d) Oxidation

A

a) Dehydration

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15
Q

What molecule does serine convert to during the deamination process?
a) Pyruvate and NH4+
b) α-ketoglutarate and NH4+
c) Acetyl-CoA and NH4+
d) Glucose and NH4+

A

a) Pyruvate and NH4+

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16
Q

How does threonine dehydratase differ from serine dehydratase in terms of the final product?
a) Threonine dehydratase produces α-ketobutyrate
b) Threonine dehydratase produces pyruvate
c) Threonine dehydratase produces alanine
d) Threonine dehydratase produces lactate

A

a) Threonine dehydratase produces α-ketobutyrate

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17
Q

What is the primary role of muscle in the transport of nitrogen to the liver?
a) Synthesizing urea for excretion
b) Utilizing branched-chain amino acids as fuel
c) Storing excess nitrogen as glutamine
d) Converting glutamate to alanine

A

b) Utilizing branched-chain amino acids as fuel

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18
Q

Which amino acid serves as the primary carrier of nitrogen from muscle to the liver?
a) Glutamine
b) Alanine
c) Aspartate
d) Glycine

A

b) Alanine

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19
Q

Why does muscle lack enzymes of the urea cycle?
a) Because muscle does not produce urea
b) Because muscle uses nitrogen for protein synthesis
c) Because urea is primarily synthesized in the liver
d) Because muscle has limited capacity for nitrogen transport

A

c) Because urea is primarily synthesized in the liver

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20
Q

What enzyme catalyzes the synthesis of glutamine from glutamate and NH4+?
a) Glutamate dehydrogenase
b) Glutamine synthetase
c) Alanine transaminase
d) Aspartate transcarbamoylase

A

b) Glutamine synthetase

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21
Q

Which enzyme catalyzes the coupling of ammonia with bicarbonate to form carbamoyl phosphate, the first step of the urea cycle?
a) Carbamoyl phosphate synthetase II
b) Argininosuccinate synthetase
c) Carbamoyl phosphate synthetase I
d) Ornithine transcarbamoylase

A

c) Carbamoyl phosphate synthetase I

22
Q

In which cellular organelle does the formation of carbamoyl phosphate occur?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Golgi apparatus

A

c) Mitochondria

23
Q

What is the key regulatory enzyme in the urea cycle?
a) Arginase
b) Ornithine transcarbamoylase
c) Carbamoyl phosphate synthetase I
d) Argininosuccinate synthetase

A

c) Carbamoyl phosphate synthetase I

24
Q

How many molecules of ATP are required for the formation of carbamoyl phosphate by carbamoyl phosphate synthetase I?
a) One
b) Two
c) Three
d) Four

A

b) Two

25
Q

Which enzyme catalyzes the transfer of the carbamoyl group of carbamoyl phosphate to ornithine, forming citrulline, in the urea cycle (step 2)?
a) Carbamoyl phosphate synthetase I
b) Arginase
c) Ornithine transcarbamoylase
d) Argininosuccinate synthetase

A

c) Ornithine transcarbamoylase

26
Q

In which cellular compartment does the reaction catalyzed by ornithine transcarbamoylase occur?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Golgi apparatus

A

c) Mitochondria

27
Q

What is formed when the carbamoyl group of carbamoyl phosphate is transferred to ornithine by ornithine transcarbamoylase?
a) Arginine
b) Citrulline
c) Aspartate
d) Urea

A

b) Citrulline

28
Q

After citrulline is formed, where is it transported for further processing in the urea cycle?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Cytoplasm

A

d) Cytoplasm

29
Q

Which molecule serves as the donor of the second nitrogen of urea in the urea cycle?
a) Citrulline
b) Aspartate
c) Arginine
d) Fumarate

A

b) Aspartate

30
Q

What enzyme catalyzes the condensation of citrulline and aspartate to form argininosuccinate in the urea cycle?
a) Carbamoyl phosphate synthetase I
b) Arginase
c) Argininosuccinate synthetase
d) Ornithine transcarbamoylase

A

c) Argininosuccinate synthetase

31
Q

In which cellular compartment does the condensation of citrulline and aspartate occur?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Cytoplasm

A

d) Cytoplasm

32
Q

What is formed when argininosuccinate is cleaved by argininosuccinase in the urea cycle?
a) Citrulline
b) Aspartate
c) Arginine
d) Fumarate

A

c) Arginine (main)
d) Fumarate

33
Q

Which enzyme hydrolyzes arginine to generate urea and ornithine in the urea cycle?
a) Carbamoyl phosphate synthetase I
b) Arginase
c) Argininosuccinase
d) Ornithine transcarbamoylase

A

b) Arginase

34
Q

What is the fate of ornithine after it is generated from the hydrolysis of arginine?
a) It is excreted in the urine
b) It is transported back into the mitochondria
c) It is converted to citrulline
d) It is utilized for protein synthesis

A

b) It is transported back into the mitochondria

35
Q

What is excreted from the body as a result of the urea cycle?
a) Citrulline
b) Aspartate
c) Arginine
d) Urea

A

d) Urea

36
Q

Where does the hydrolysis of arginine occur in the urea cycle?
a) Mitochondria
b) Nucleus
c) Endoplasmic reticulum
d) Cytoplasm

A

d) Cytoplasm

37
Q

What is the primary consequence of defects in the urea cycle?
a) Hypoammonemia
b) Hyperglycemia
c) Hyperammonemia
d) Hypoglycemia

A

c) Hyperammonemia

38
Q

How does high levels of NH4+ impact nerve cells?
a) By enhancing osmotic balance
b) By reducing cellular swelling
c) By activating neurotransmitter systems
d) By disrupting the osmotic balance and causing cellular swelling

A

d) By disrupting the osmotic balance and causing cellular swelling

39
Q

Which cellular transporter may be inappropriately activated by high levels of NH4+ in nerve cells?
a) Na+-K+-ATPase
b) Ca2+-ATPase
c) Na+-K+-Cl– cotransporter
d) Glucose transporter

A

c) Na+-K+-Cl– cotransporter

40
Q

Apart from disrupting osmotic balance, what other cellular functions can be impacted by high NH4+ levels?
a) Synthesis of DNA
b) Regulation of cell cycle
c) Energy metabolism, oxidative stress, and signal transduction pathways
d) Protein folding

A

c) Energy metabolism, oxidative stress, and signal transduction pathways

41
Q

Which type of amino acids are degraded to acetyl CoA or acetoacetyl CoA and can give rise to ketone bodies or fatty acids?
a) Glucogenic amino acids
b) Ketogenic amino acids
c) Branched-chain amino acids
d) Aromatic amino acids

A

b) Ketogenic amino acids

42
Q

What can glucogenic amino acids be used to produce?
a) Ketone bodies
b) Fatty acids
c) Glucose
d) Amino acids

A

c) Glucose

43
Q

Which amino acids are solely ketogenic?
a) Isoleucine and phenylalanine
b) Leucine and lysine
c) Tryptophan and tyrosine
d) Methionine and histidine

A

b) Leucine and lysine

44
Q

Which amino acids are both ketogenic and gluconeogenic?
a) Leucine and lysine
b) Isoleucine and phenylalanine
c) Tryptophan and tyrosine
d) Valine and glycine

A

c) Tryptophan and tyrosine
( Isoleucine, phenylalanine, tryptophan, and tyrosine)

45
Q

degradation products of pyruvate

A

glucogenic:
- alanine
- cysteine
- glycine
- serine
- threorine
- tryptophan

46
Q

degradation products of oxaloacetate

A

glucogenic:
asparagine
aspartate

47
Q

degradation products of fumarate

A

glucogenic:
aspartate
phenylalanine
tyrosine

48
Q

degradation products of succinyl CoA

A

glucogenic:
Ile
Met
Thr
Val

49
Q

degradation products of alpha-ketoglutarate

A

glucogenic:
Arg
Glu
Gln
His
Pro

50
Q

degradation products of acetyl Coa

A

ketogenic:
Ile
Leu
Trp

51
Q

degradation products of acetoacetyl CoA

A

ketogenic:
Leu
Lys
Phe
Trp
Tyr

biochem 2 (6 decks)

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