BCM Midterm Homework

Alimentation and the following degradation of proteins provide cells with:

 

carbohydrates.

 

fatty acids.

 

amino acids.

 

nucleic acids.

 

lipids.

amino acids

What amino acid is essential?

 

serine

 

glycine

 

proline

 

valine

 

asparagine

valine

Which amino acids are degraded by muscles?

 

Val, Leu, Ile

 

Val, Met, Leu

 

Met, Leu, Val

 

Ile, Gly, Met

 

Leu, Gly, Met

Val, Leu, Ile

Which enzyme family does argininosuccinase belong to?

 

ligases

 

lyases

 

transferases

 

synthetases

 

kinases

lyases

Urea is synthesized in the:

 

intestines.

 

kidneys.

 

pancreas.

 

spleen.

 

liver.

liver.

Choose the reaction in which amino acids could be synthesized from α-ketoacids.

 

hydroxylation reaction

 

acylation reaction

 

phosphorylation reaction

 

transamination reaction

 

transpeptidation reaction

transamination reaction

What prosthetic group do aminotransferases contain?

 

amino group

 

carboxy group

 

pyridoxal phosphate group

 

phosphoryl group

 

methyl group

pyridoxal phosphate group

What is the MOST significant functional group in the pyridoxal phosphate group?

 

ketone

 

amino group

 

aldehyde

 

methyl group

 

carboxyl group

aldehyde

Ketogenic amino acids that degrade into acetyl CoA can give rise to:

 

amino acids.

 

fatty acids.

 

nucleic acids.

 

lipids.

 

carbohydrates.

fatty acids.

What amino acids are solely ketogenic?

 

Leu, Val

 

Val, Gly

 

Lys, Leu

 

Gly, Leu

 

Lys, Val

Lys, Leu

What amino acids have both ketogenic and glucogenic properties?

 

Tyr, Val, Trp, Asp

 

Trp, Ile, Tyr, Phe

 

Ile, Met, His, Ala

 

Phe, Glu, Asn, Lys

 

Val, Ala, Asn, Tyr

Trp, Ile, Tyr, Phe

The half-life of a cytosolic protein is primarily determined by the:

 

length of the protein chain.

 

amino terminal residue.

 

sequence at the carboxyl terminus.

 

presence of repeated sequences.

 

three-dimensional structure.

amino terminal residue.

What protein has the longest life in the human organism?

 

ubiquitin

 

ornithine decarboxylase

 

hemoglobin

 

crystallin

 

insulin

crystallin

What is the mechanism of ubiquitin binding to the target protein?

 

ε-Amino groups of lysine residue on the targeted protein covalently connect with the C-terminal glycine residue of ubiquitin.

 

ε-Amino groups of glycine residue on the targeted protein covalently connect with the C-terminal lysine residue of ubiquitin.

 

ε-Amino groups of lysine residue on the targeted protein covalently connect with the N-terminal glycine residue of ubiquitin.

 

ε-Amino groups of glycine residue on the targeted protein covalently connect with the N-terminal lysine residue of ubiquitin.

 

α-Amino groups of glycine residue on the targeted protein covalently connect with the N-terminal lysine residue of ubiquitin.

ε-Amino groups of lysine residue on the targeted protein covalently connect with the C-terminal glycine residue of ubiquitin.

How many enzymes take part in the binding of ubiquitin to the targeted protein?

 

1

 

2

 

3

 

4

 

5

3

What amino-terminus amino acids are highly destabilizing and prefer rapid ubiquitination?

 

methionine and leucine

 

valine and serine

 

serine and isoleucine

 

isoleucine and valine

 

arginine and leucine

arginine and leucine

What enzyme is the amino-terminal reader?

 

ubiquitin activating enzyme

 

ubiquitin-protein ligase

 

ubiquitin-conjugating enzyme

 

monooxygenase

 

aminotransferas

ubiquitin-protein ligase

The overexpression of ubiquitin-protein ligase is associated with:

 

Angelman syndrome.

 

unusually happy disposition.

 

autism.

 

uncoordinated movement.

 

absence of speech.

autism.

What process is NOT controlled by protein degradation through the ubiquitin-proteasome pathway?

 

Gene translation

 

organ formation

 

circadian rhythms

 

cholesterol metabolism

 

tumor suppression

Gene translation

A synonym of aminotransferases is:

 

aminopeptidases.

 

monooxygenases.

 

aminotransferases.

 

reductases.

 

transaminases.

transaminases

An allosteric inhibitor of glutamate dehydrogenase is:

 

GTP.

 

ATP.

 

AMP.

 

ADP.

 

NADH.

GTP.

Aspartate aminotransferase belongs to:

 

monooxygenases.

 

pyridoxal-dependent transaminases.

 

reductases.

 

transaminases.

 

decarboxylases.

pyridoxal-dependent transaminases.

What aminotransferases are the indicators of liver damage if detected in blood?

 

valine, serine, methionine

 

alanine, serine, valine

 

aspartate, alanine

 

methionine, alanine

 

serine, aspartate

aspartate, alanine

Choose the CORRECT substrates for carbamoyl phosphate synthetase. Select all that apply.

 

NH₄⁺

 

NH₃

 

HCO₃^–

 

NADH

 

GTP

NH₃

 

HCO₃^–

How many equivalent molecules of ATP should be consumed to synthesize one urea molecule?

 

1

 

2

 

3

 

4

 

5

4

In liver, arginine hydrolyzes to:

 

glutamate and urea.

 

aspartate and fumarate.

 

fumarate and succinate.

 

citrulline and ornithine.

 

ornithine and urea.

ornithine and urea.

Pyruvate is the entry point in the citric acid cycle for:

 

cysteine, leucine, and proline.

 

valine, leucine, and isoleucine.

 

tyrosine, lysine, and valine.

 

cysteine, alanine, and serine.

 

serine, histidine, and valine.

cysteine, alanine, and serine.

Asparaginase catalyzes the reaction of asparagine transformation into:

 

aspartate and NH₄⁺.

 

glutamate and oxaloacetate.

 

pyruvate and NH₄⁺.

 

pyruvate and glutamate.

 

oxaloacetate and aspartate.

aspartate and NH₄⁺.

The degradative pathways of Ile and Val are common to:

 

glycine.

 

leucine.

 

lysine.

 

glutamine.

 

serine.

leucine.

What enzyme is absent or deficient in the case of phenylketonuria?

 

phenylalanine transaminase

 

phenylalanine N-methyltransferase

 

phenylalanine N-acetyltransferase

 

phenylalanine hydroxylase

 

monooxygenase

phenylalanine hydroxylase

Which amino acid is an important precursor to dopamine?

 

serine

 

tyrosine

 

valine

 

threonine

 

isoleucine

tyrosine

Surplus amino acids are:

 

stored in proteasomes.

 

stored in protein scaffolds.

 

used as the metabolic fuel.

 

stored as albumin.

 

stored as glycogen.

used as the metabolic fuel.

The primary proteolytic enzyme of the stomach is:

 

trypsin.

 

chymotrypsin.

 

elastase.

 

carboxypeptidase A.

 

pepsin.

pepsin.

Which amino acids can be directly deaminated to produce NH₄⁺?

 

serine and threonine

 

serine, asparagine, and threonine

 

proline and threonine

 

proline and valine

 

proline and serine

serine and threonine

In the urea cycle, the second nitrogen of urea enters the cycle in the form of which metabolite?

 

alanine

 

glutamine

 

ornithine

 

aspartate

 

arginine

aspartate

Which amino acid is a metabolite in the urea cycle but is not used as a building block of proteins?

 

ornithine

 

aspartate

 

glutamate

 

lysine

 

arginine

ornithine

Ammoniotelic organisms excrete excess nitrogen as:

 

xanthine.

 

NH₄⁺.

 

urea.

 

uric acid.

 

arginine.

NH₄⁺.

What is a product of transamination of aspartate and α-ketoglutarate?

 

glutamine

 

asparagine

 

pyruvate

 

oxaloacetate

 

glucose

oxaloacetate

What is a product of ketogenic amino acids degradation?

 

pyruvate

 

acetoacetate

 

oxaloacetate

 

α-ketoglutarate

 

argininosuccinate

acetoacetate

Which amino acids supply carbons as succinyl CoA for eventual entry into metabolism?

 

Met, Val, Leu

 

Met, Ile, Val

 

Ile, Val, Leu

 

Ile, Leu, Gly

 

Val, Gly, Ile

Met, Ile, Val

What product of the first step of methionine degradation is an important methyl group donor?

 

5-methyltetrahydrofolate

 

methylcobalamin

 

S-adenosylmethionine

 

S-adenosylhomocysteine

 

propionyl CoA

 

S-adenosylmethionine

What class of enzymes cleaves most aromatic rings in biological systems?

 

dioxygenases

 

monooxygenases

 

biopterin-linked lyases

 

aromatic oxidases

 

aminotransferases

dioxygenases

What term describes a specific sequence of amino acids that indicates that a particular protein should be degraded?

 

consensus sequence

 

proteasome recognition sequence

 

degron

 

ubiquitin binding domain

 

intron

degron

What is the MOST common phospholipid in mammals?

 

cerebroside

 

ganglioside

 

phosphatidylcholine

 

phosphatidylethanolamine

 

phosphatidylserine

phosphatidylcholine

Which alcohol is required for the formation of cardiolipin from cytidine diphosphodiacylglycerol (CDP-diacylglycerol)?

 

choline

 

ethanolamine

 

inositol

 

phosphatidylglycerol

 

sphingosine

phosphatidylglycerol

What phospholipid is synthesized after phosphorylation of an alcohol, but not diacylglycerol?

 

diphosphatidylglycerol

 

phosphatidylcholine

 

phosphatidylinositol

 

phosphatidylserine

 

triacylglycerols

phosphatidylinositol

What metabolite is produced from phosphatidate by the action of phosphatidic acid phosphatase?

 

diacylglycerol

 

diacylglycerol 3-phosphate

 

dihydroxyacetone phosphate

 

glycerol 3-phosphate

 

lysophosphatidate

diacylglycerol

The cofactor in the rate-limiting step in sphingolipids synthesis is:

 

FAD.

 

HSKoA.

 

NADH.

 

pyridoxal phosphate.

 

thiaminpyrophosphate.

pyridoxal phosphate.

What is used for replacement of the terminal hydroxyl group of ceramide to yield sphingomyelin?

 

phosphorylcholine

 

phosphatidylserine

 

UDP-N-acetylgalactosamine

 

UDP-galactose

 

UDP-glucose

phosphorylcholine

What enzyme catalyzes the formation of phosphatidate from diacylglycerol?

 

CTP-phosphocholine cytidylyltransferase

 

diacylglycerol kinase

 

diglyceride acyltransferase

 

glycerol phosphate acyltransferase

 

phosphatidic acid phosphatase

diacylglycerol kinase

What can be synthesized by the methylation of phosphatidylethanolamine?

 

ceramide

 

phosphatidic acid

 

phosphatidylcholine

 

phosphatidylinositol

 

phosphatidylserine

phosphatidylcholine

What nucleoside triphosphate activates both phosphatidate in phosphatidylinositol synthesis and phosphorylethanolamine in the phosphatidylethanolamine biosynthetic pathway?

 

ATP

 

CTP

 

GTP

 

TTP

 

UTP

CTP

What is the product of the committed step in cholesterol biosynthesis?

 

3-isopentyl pyrophosphate

 

dimethylallyl pyrophosphate

 

farnesyl pyrophosphate

 

mevalonate

 

squalene

mevalonate

Choose the statement that does NOT describe the regulation of cholesterol biosynthesis through 3-hydroxy-3-methylglutaryl CoA reductase.

 

The rate of synthesis of reductase mRNA is controlled by the sterol regulatory element binding protein.

 

When cholesterol levels are high, SREBP induces production of the reductase.

 

Metabolites derived from mevalonate decrease the rate of translation of reductase mRNA.

 

After extraction of the reductase from the membrane, it is degraded in the presence of ubiquitin.

 

Cholesterol synthesis ceases when the AMP level is high.

When cholesterol levels are high, SREBP induces production of the reductase.

What enzyme catalyzes the final stage of cholesterol biosynthesis?

 

3-hydroxy-3-methylglutaryl CoA reductase

 

CTP-phosphocholine cytidylyltransferase

 

geranyl transferase

 

oxidosqualene cyclase

 

squalene synthase

oxidosqualene cyclase

Which lipoprotein particles play a major role in the transport of triacylglycerols from the liver to other tissues?

 

chylomicrons

 

chylomicron remnants

 

very low-density lipoproteins (VLDLs)

 

intermediate-density lipoproteins (IDLs)

 

low-density lipoproteins (LDLs)

very low-density lipoproteins (VLDLs)

Which lipoprotein particles are the major carriers of cholesterol esters in blood?

 

chylomicrons

 

high-density lipoproteins (HDLs)

 

very low-density lipoproteins (VLDLs)

 

intermediate-density lipoproteins (IDLs)

 

low-density lipoproteins (LDLs)

low-density lipoproteins (LDLs)

What is the MOST common fatty acid chain in cholesterol esters in lipoprotein particles in blood?

 

linoleate

 

linolenate

 

oleate

 

palmitate

 

palmitoleate

linoleate

Which lipoprotein particles play a central role in reverse cholesterol transport?

 

chylomicrons

 

high-density lipoproteins (HDLs)

 

intermediate-density lipoproteins (IDLs)

 

low-density lipoproteins (LDLs)

 

very low-density lipoproteins (VLDLs)

high-density lipoproteins (HDLs)

What plays a central role in cholesterol metabolism?

 

b-adrenergic receptors

 

HLDL receptors

 

IDL receptors

 

LDL receptors

 

VLDL receptors

LDL receptors

What enzyme catalyzes the hydroxylation reactions in the synthesis of cortisol from progesterone?

 

5α-reductase

 

P450 monooxygenase

 

cytochrome c oxidase

 

desmolase

 

HMG-CoA reductase

 

P450 monooxygenase

What enzyme catalyzes the hydroxylation reactions in the synthesis of taurocholate from cholesterol?

 

aromatase

 

P450 monooxygenase

 

HMG-CoA reductase

 

mevalonate kinase

 

squalene synthase

 

P450 monooxygenase

What is the basic five-carbon building block for the synthesis of terpenes, vitamin K, and coenzyme Q₁₀?

 

5-pyrophosphomevalonate

 

farnesyl pyrophosphate

 

geranyl pyrophosphate

 

geranylgeranyl pyrophosphate

 

isopentenyl pyrophosphate

isopentenyl pyrophosphate

\

The basic building block for the synthesis of lycopene and β-carotene is:

 

5-pyrophosphomevalonate.

 

farnesyl pyrophosphate.

 

geranylgeranyl pyrophosphate.

 

mevalonate.

 

squalene.

geranylgeranyl pyrophosphate.

The precursor of glucocorticoids is:

 

7-dehydrocholesterol.

 

17α-hydroxyprogesterone.

 

androstenedione.

 

deoxycorticosterone.

 

pregnenolone.

pregnenolone

What is formed from testosterone?

 

aldosterone

 

androstenedione

 

cortisol

 

estradiol

 

estrone

estradiol

Choose the vitamin whose deficiency leads to osteomalacia.

 

vitamin A

 

vitamin D

 

vitamin E

 

vitamin K

 

vitamin PP

vitamin D

The precursor of mineralocorticoids is:

 

7-dehydrocholesterol.

 

17α-hydroxyprogesterone.

 

5-dihydrotestosterone.

 

androstenedione.

 

progesterone.

progesterone

What vitamin is produced in the skin by ultraviolet light?

 

vitamin A

 

vitamin D

 

vitamin E

 

vitamin K

 

vitamin H

vitamin D

What is the major site of triacylglycerol synthesis in mammals?

 

liver

 

adipose tissue

 

small intestine

 

kidneys

 

pancreas

liver

Phosphatidate is formed from:

 

glycerol 3-phosphate and two fatty acyl CoAs.

 

glycerol and two free fatty acids.

 

pyruvate and triacylglycerol.

 

glycerol and two fatty acyl CoAs.

 

glycerol 3-phosphate and diacylglycerol.

glycerol 3-phosphate and two fatty acyl CoAs.

What metabolite is the source of all carbons for cholesterol?

 

glucose

 

pyruvate

 

succinyl CoA

 

oxaloacetate

 

acetyl CoA

acetyl CoA

The immediate product of HMG-CoA reductase in the cholesterol synthesis pathway is:

 

isopentenyl pyrophosphate.

 

mevalonate.

 

squalene.

 

farnesyl pyrophosphate.

 

acetoacetyl CoA.

mevalonate.

The major component of low-density lipoproteins is:

 

sphingomyelin.

 

free cholesterol.

 

triacylglycerol.

 

cholesteryl linoleate.

 

apo B-100.

cholesteryl linoleate.

What is the primary bile salt?

 

aldosterone

 

pregnenolone

 

cortisol

 

glycocholate

 

taurocholate

glycocholate

The major carrier(s) of dietary fat from the intestine is/are:

 

VLDL.

 

chylomicrons.

 

HDL.

 

LDL.

 

IDL.

chylomicrons.

Which derivative of cholesterol is the precursor of the steroid hormones?

 

aldosterone

 

progesterone

 

cortisol

 

androstenedione

 

pregnenolone

pregnenolone

The energy for the conversion of provitamin D₃ into vitamin D₃ comes from:

 

ATP hydrolysis.

 

NADPH oxidation.

 

thioester hydrolysis.

 

ultraviolet light from the sun.

 

visible light from the sun.

ultraviolet light from the sun.

The precursor of which substance combines with glycine to form a major bile salt?

 

phosphatidate

 

phosphatidylethanolamine

 

glycerol

 

cholesterol

 

phosphatidylserine

cholesterol

Hydroxylation of cholesterol by cytochrome P450 requires:

 

NADPH and thiamine.

 

O₂ and PLP.

 

PLP and thiamine.

 

thiamine and O_2.

 

NADPH and O_2.

NADPH and O_2.

A pyrimidine base linked to a sugar and phosphorylated at 5' is called a:

 

nucleotide.

 

nucleoside.

 

ribonucleoside.

 

deoxynucleoside.

 

pyrimidinylate.

nucleotide

Choose the correct answer. DNA is built from:

 

nucleotides.

 

nucleosides.

 

deoxyribonucleotides.

 

ribonucleotides.

 

deoxyribonucleosides.

deoxyribonucleotides

The first step in de novo pyrimidine biosynthesis is the:

 

cleavage of two molecules of ATP.

 

synthesis of carbamoyl phosphate from bicarbonate and ammonia.

 

phosphorylation of carbamic acid by a molecule of ATP.

 

reaction of carbamoyl phosphate with aspartate to form carbamoylaspartate.

 

attachment to ribose phosphate.

synthesis of carbamoyl phosphate from bicarbonate and ammonia.

Which reaction is NOT carried out by carbamoyl phosphate synthetase II?

 

glutamine hydrolysis

 

phosphorylation of bicarbonate

 

formation of carbon–nitrogen bonds through acylphosphate intermediates

 

phosphorylation of carbamic acid

 

ammonia incorporation into urea

ammonia incorporation into urea

Which substrate is NOT needed for de novo synthesis of pyrimidines?

 

ribose 5-phosphate

 

aspartate

 

glutamate

 

glutamine

 

bicarbonate

glutamate

Which molecule is NOT part of pyrimidine nucleotides?

 

orotidylate

 

uridylate

 

cytidylate

 

xanthylate

 

thymidylate

xanthylate

Which molecule is NOT the part of purine nucleotides?

 

inosinate

 

orotidylate

 

adenylosuccinate

 

xanthylate

 

guanylate

orotidylate

Which enzyme does NOT catalyze the substitution of a phosphoryl group for an amino group?

 

aspartate transcarbamoylase

 

carbamoyl phosphate synthetase II

 

carbamoyl phosphate synthetase I

 

uridine monophosphate synthetase

 

cytidine triphosphate synthetase

 

uridine monophosphate synthetase

Choose the enzyme that performs without substrate channeling within it.

 

glutamine phosphoribosyl amidotransferase

 

tryptophan synthetase

 

CAD of mammals

 

ribonucleotide reductase

 

carbamoyl phosphate synthetase II

ribonucleotide reductase

Choose the enzyme that catalyzes reactions of the general equation XDP + YTP —> XTP + YDP.

 

nucleoside phosphorylase

 

nucleoside diphosphate kinase

 

nucleoside triphosphate phosphorylase

 

nucleoside triphosphate synthetase

 

nucleotide reductase

nucleoside diphosphate kinase

What is the committed step in purine nucleotide biosynthesis?

 

the conversion of PRPP to phosphoribosylamine

 

the cyclization of 5-formaminoimidazole-4-carboxamide ribonucleotide to form inosinate

 

the attachment of a glycine residue to 5-phosphoribosyl-1-amine

 

the oxidation of inosinate to xanthylate

 

the elimination of fumarate

the conversion of PRPP to phosphoribosylamine

The conversion of ribonucleotides to deoxyribonucleotides is catalyzed by:

 

nucleoside phosphorylase.

 

ribonucleotide reductase.

 

nucleoside diphosphate kinase.

 

dihydrofolate reductase.

 

catalase.

ribonucleotide reductase.

What is the intermediate in the conversion of inosinate into adenylate?

 

guanylate

 

hypoxanthine

 

adenylosuccinate

 

orotidylate

 

xanthylate

adenylosuccinate

What is used by ribonucleotide reductase as the direct source of electrons?

 

NADPH

 

FADH₂

 

thioredoxin

 

ubiquinol

 

NADH

thioredoxin

Choose the compound that is NOT designed for cancer therapy targeting ribonucleotide reductase.

 

clofarabine

 

gemcitabine

 

amethopterin

 

cladribine

 

dATP analogs

amethopterin

Choose the nucleotide whose synthesis is widely exploited in the treatment of cancer.

 

dAMP

 

TTP

 

IMP

 

dGMP

 

dCTP

TTP

Which statement about the synthesis of PRPP from ribose 5-phosphate by PRPP synthetase is INCORRECT?

 

It is the committed step in purine synthesis.

 

It is allosterically regulated by nucleotides.

 

It is inhibited by IMP.

 

It is inhibited by AMP.

 

It is inhibited by GMP.

It is the committed step in purine synthesis.

How is aspartate transcarbamoylase (ATCase) regulated?

 

ATCase is inhibited by CTP and stimulated by ATP.

 

ATCase is inhibited by ATP and stimulated by CTP.

 

ATCase is inhibited by UMP and stimulated by ATP.

 

ATCase is inhibited by ATP and stimulated by UMP.

 

ATCase is inhibited by CTP and UMP.

ATCase is inhibited by CTP and stimulated by ATP.

What is the main step for the regulation of pyrimidine biosynthesis in bacteria?

 

oxidation of dihydroorotate by NAD⁺ to form orotate

 

formation of carbamoylaspartate

 

orotate coupling to PRPP

 

phosphorylation of bicarbonate by ATP

 

phosphorylation of carbamic acid

formation of carbamoylaspartate