Amino Acid Biochemistry 2023

Question 1 of 110

Which of the following statements is correct regarding glutamate?

In transamination, glutamate is produced when a ketoacid accepts an amine group from another molecule.
It is produced by oxidation of arginine.
Its synthesis occurs when glutamine gains an amine group.
None of the other answer options is correct.
It is an important precursor of aspartate.

Question 2 of 110

Two cysteine molecules are produced by one chemical reaction from…?

L-cystine
Serine
Selenocysteine
L-cysteic acid
Homocysteine

Question 3 of 110

Which of the following is true regarding the glucose-alanine cycle?

Alanine transaminase is not involved.
Transamination does not occur.
Hydroxylation does not occur.
Gluconeogenesis does not occur.
Glycolysis does not occur

Question 4 of 110

Which of the following is true regarding nitrogen in the body?

Nitrogen is not needed for the synthesis of ornithine.
Proper balance of nitrogen is critical.
Nitrogen is needed for fatty acid synthesis.
Nitrogen is not needed for the synthesis of nucleotides.
Nitrogen is only needed for protein-based amino acids

Question 5 of 110

Which of the following enzymes is expressed in the liver cells only?

Carbamoyl phosphate synthetase
Arginase
Ornithine transcarbamylase
Argininosuccinate synthetase
Argininosuccinate lyase

Question 6 of 110

Which of the following is true about iron?

Iron is easily excreted from the body via the kidneys.
It can help to break down free radicals using the Fenton reaction.
It can gain or lose electrons depending on its oxidative state.
It is needed in large amounts in the body.
It can react with water to form a peroxyl radical.

Question 7 of 110

Which of the following is NOT true regarding the phenomenon of cooperativity?

The binding of oxygen on the hemoglobin molecule enhances the affinity of adjacent binding sites for oxygen.
Cooperativity of hemoglobin toward oxygen binding in the lungs shows conformational changes from the T state to the R state.
Myoglobin changes from a relaxed to a tight state at high oxygen concentration levels, favoring oxygen binding.
The binding of a ligand to one of the binding sites increases or decreases the affinity of the other binding sites to the ligand.
Cooperativity is displayed by systems having dependently acting identical or near-identical subunits.

Question 8 of 110

Which of the following is true regarding sickle cell anemia?

The homozygous form of the disease provides the best protection against malaria.
The complications arise from sickled red blood cells getting stuck in capillaries.
Sickled cells move through capillaries easier than normal cells.
The sickled cells are removed from the circulation by the liver.
The sickling of blood cells occurs upon the binding of oxygen.

Question 9 of 110

What molecular change occurs during the process of transamination?

One amine group on one molecule is exchanged with another amine group on another molecule.
Carboxylation accompanies amine group addition.
Carbons are exchanged between 2 molecules.
An amine group swaps with carbonyl oxygen.
Decarboxylation occurs.

Question 10 of 110

Which of the following is true of branched chain amino acid synthesis?

It begins with α-ketobutyrate.
Valine and isoleucine pathways involve adding a two-carbon piece to pyruvate.
It favors isoleucine when valine is low.
It is regulated by threonine deaminase.
They start with decarboxylation and the addition of a three-carbon piece.

Question 11 of 110

Which of the following is true regarding nitrogen excretion?

Ammonotelic organisms excrete uric acid.
The uricotelic organisms excrete urea.
The uricotelic organisms are mainly humans.
The ureotelic organisms include most vertebrates.
The ammonotelic organisms are primarily birds.

Question 12 of 110

Citrulline gets transported out of the mitochondrion via which of the following options?

Citrulline translocase
Sodium/Potassium ATPase
Ornithine-citrulline translocase
Ornithine translocase
Argininosuccinate translocase

Question 13 of 110

Which protein is involved in iron transit within secretory fluids?

Cytochrome
Myoglobin
Lactoferrin
Ferritin
Catalase

Question 14 of 110

Which of the following are NOT correctly matched?

Oxygen and hemoglobin — Cooperativity
Oxygen affinity curve for myoglobin — Hyperbolic
Binding of oxygen to myoglobin — Low concentrations of oxygen
Cooperativity — binding of oxygen to myoglobin
Oxygen affinity curve for hemoglobin — Sigmoidal

Question 15 of 110

Which statement is NOT true regarding fetal hemoglobin?

Fetal hemoglobin always stays in a relaxed state, hence it is capable of uptake of oxygen at a rapid rate from the maternal blood.
Fetal hemoglobin does not bind with 2,3-bisphosphoglycerate.
Fetal hemoglobin is comprised of two alpha and two beta subunits.
Fetal hemoglobin releases oxygen more readily than myoglobin, but to a lesser extent than adult hemoglobin
The oxygen affinity, in order, is myoglobin > fetal HB > adult HB.

Question 16 of 110

The conversion of glutamate to glutamine catalyzed by glutamine synthetase results in which of the following?

Production of ATP
Production of a toxic product
Phosphorylation of ADP
Release of urea
Removal of ammonia

Question 17 of 110

Methionine is produced from homocysteine by…?

…phosphorylation.
…adding a carboxyl group.
…succinylation.
…the addition of a methyl group to the sulfur atom.
…loss of ammonium ion.

Question 18 of 110

Which amino acid is the main precursor of thyroid hormones?

Phenylalanine
Tyrosine
Lysine
Methionine
Selenocysteine

Question 19 of 110

Which of the following is true regarding glutamic acid?

It is not central to the body’s amine metabolism/transfer
The addition of pyruvate to glutamic acid yields glutamine.
It becomes α-ketoglutarate by the loss of an amine.
It becomes α-ketoglutarate by the gain of an amine
It becomes glutamine by the loss of an amine.

Question 20 of 110

Which enzyme deficiency is NOT correctly associated with the resulting disorder?

Argininosuccinate lyase — Argininosuccinic aciduria
Argininosuccinate synthetase — Citrullinemia
Carbamoyl phosphate synthetase — Carbamoyl phosphate synthetase I deficiency
Ornithine transcarbamylase — Carbamoyl phosphate deficiency
Arginase — Argininemia

Question 21 of 110

Which of the following is true regarding transferrin?

It has a very poor affinity for iron.
It transfers its iron to intracellular ferritin
It can carry hundreds of iron atoms.
It is slow in the transferring of its iron.
It is a lipoprotein.

Question 22 of 110

Which of the following is true regarding 2,3 bisphosphoglycerate (2,3 BPG)?

It is produced by rapidly metabolizing tissue.
Increases in 2,3 BPG shift the oxygen-hemoglobin dissociation curve to the left.
It binds the heme portion of hemoglobin.
It locks hemoglobin into the R state.
It increases hemoglobin's ability to carry oxygen.

Question 23 of 110

What mutation in the hemoglobin protein causes the most common form of sickle cell anemia?

The normal valine present at the 16th position is replaced by glutamic acid.
The normal glutamic acid present at the 6th position is replaced by valine.
The normal glutamic acid present at the 60th position is replaced by valine.
The normal glutamic acid present at the 16th position is replaced by valine.
The normal valine present at the 6th position is replaced by glutamic acid.

Question 24 of 110

Which of the following reactions is not responsible for producing cellular ammonia?

Amino acid metabolism
All of the reactions listed are a source of cellular ammonia.
Decarboxylation
Glutamate oxidation
Nitrite reduction

Question 25 of 110

The first three steps in the synthesis of threonine are the same as the first three steps in the synthesis of…?

…lysine
…aspartate.
…serine.
…methionine.

Question 26 of 110

Which enzyme converts thyroxine into triiodothyronine?

Deiodinase
Tyrosine transaminase
4-fumaryl acetoacetase
Aromatic acid decarboxylase
Dopamine-β-hydroxylase

Question 27 of 110

Which of the following is true regarding the urea cycle?

Water is not needed for the reaction to occur.
It outputs 3 amines per turn of the cycle.
It generates ATP.
It primarily occurs in the muscles.
Two amines are used in the reaction that forms urea.

Question 28 of 110

Which of the following causes mutations in DNA molecules?

Peroxynitrite
Molecular oxygen
Cysteine
Tyrosine
Proteins

Question 29 of 110

Which of the following are true regarding ferritin?

It stores iron in the ferrous state
It stores two atoms of ferrous iron per complex
All of the answers are true
None of the answers are true
It is present in low amounts in iron deficiency anemia

Question 30 of 110

Which of the following is true regarding rapidly metabolizing tissues?

They absorb oxygen.
They absorb protons.
They absorb CO2.
They absorb 2,3 BPG.
Have a relative increase in pH.

Question 31 of 110

What is the cause of sickling in sickle cell disease?

Trimeric hemoglobin at high oxygen concentrations
Polymeric hemoglobin at low oxygen concentrations
Dimeric hemoglobin at high oxygen concentrations
Monomeric hemoglobin at low oxygen concentrations
Polymeric hemoglobin at high oxygen concentrations

Question 32 of 110

Which of the following statements regarding lysine metabolism is NOT correct?

Lysine is one of the most post-translationally modified amino acids.
α-aminoadipic semialdehyde synthase deficiency leads to hyperlysinemia.
The deficiency of one of the enzymes in the lysine synthesis pathway leads to hyperlysinemia.
The first two reactions in the synthesis of lysine, threonine, and methionine are the same.
Hyperlysinemia is the accumulation of lysine in the blood.

Question 33 of 110

Which of the following statements is not true?

Thyroglobulin protein participates in the synthesis of T4 and T3 hormones in the thyroid gland.
The treatment of tyrosinemias and phenylketonuria involves the restriction of intake of amounts of tyrosine and phenylalanine in the individual’s diet.
There are two types of iodine-containing thyroid hormones: triiodothyronine (T3) and thyroxine (T4).
Iodide ions, essential for the production of thyroid hormones, are grabbed from the blood and transported into the thyroid follicular cell via sodium-iodide symport.
Alkaptonuria is a rare inherited genetic disorder in which the body breaks the tyrosine at very rapid rates and leads to the accumulation of fumarate and acetoacetate in the body.

Question 34 of 110

Which of the following is true regarding ornithine transcarbamylase?

It requires ATP.
It is the least commonly deficient enzyme in the urea cycle.
It has an autosomal inheritance.
It catalyzes the formation of citrulline.
It catalyzes the formation of ornithine.

Question 35 of 110

Which of the following is true of a transferrin receptor?

None of the answers are true
It is a cytoplasmic protein
All of the answers are true
It is expressed in decreased amounts when cellular iron levels are low
It is a glycoprotein

Question 36 of 110

Which of the following is true regarding smokers?

2,3 BPG levels fall.
High 2,3 BPG levels favor the R state, so oxygen is retained.
They are more likely to have increased 2,3 BPG levels.
2,3 BPG binds myoglobin.
Low levels of 2,3 BPG favor the T state, so oxygen is released.

Question 37 of 110

What region of the world is it advantageous to have a copy of the sickle cell gene?

Hepatitis-prevalent regions of the world
Jaundice-prevalent regions of the world
Cryptosporidiosis-prevalent regions of the world
HIV-prevalent regions of the world
Malaria-prevalent regions of the world

Question 38 of 110

Which of the following is true regarding arginine?

It is made primarily of nitric oxide.
All of the answers are true.
It is an important precursor of urea.
None of the answers are true.
It is produced by catalysis of arginase.

Question 39 of 110

Which is true of the aromatic amino acid family?

All of the answers are true.
It includes phenylalanine, tyrosine, and threonine.
None of the answers are true.
It is made primarily from neurotransmitters.
Each member is synthesized from phosphoenolpyruvate (PEP) and erythrose-4-phosphate.

Question 40 of 110

Which of the following is not correctly associated?

Tyrosinemia I—4-Fumarylacetoacetase deficiency
Tyrosinemia II—Tyrosine transaminase deficiency
Tyrosinemia III—p-Hydroxyphenylpyruvate dioxygenase deficiency
Alkaptonuria—Homogentisate 1,2-dioxidase deficiency
Phenylketonuria—4-Fumarylacetoacetase deficiency

Question 41 of 110

Which of the following is true regarding the alternate metabolism of citrulline?

One citrulline is produced.
ATP is required.
Arginine is produced.
Nitric oxide is required.
Nitric oxide synthase can be used.

Question 42 of 110

Which of the following is true regarding the iron response element (IRE)?

It occurs near the 3' end of the ferritin mRNA.
It is bound by the IRE-BP when iron concentration is low.
It is a protein.
It allows the ribosome to perform translation when bound to the IRE-BP.
It binds to iron when the iron concentration is high.

Question 43 of 110

Which of the following is true regarding carbon monoxide?

It binds hemoglobin in the same place as carbon dioxide
It binds to the donut of the hemoglobin.
It increases hemoglobin's oxygen-carrying capacity.
It helps hemoglobin release oxygen to rapidly metabolizing tissues.
It is higher in the blood of smokers.

Question 44 of 110

Which of the following is true regarding bilirubin?

It is usually high in concentration in hepatic or pancreatic diseases.
Conjugated bilirubin in the urine may indicate kidney disease.
It causes jaundice only when its unconjugated form is increased.
High levels of bilirubin in the brain are neuroprotective.
It is consumed by intestinal flora.

Question 45 of 110

Which of the following compounds is not produced directly from arginine?

Nitric oxide
Ornithine
ADMA
Ammonia
Citrulline

Question 46 of 110

Which of the following apply to branched chain amino acid catabolism?

It produces NADH.
It produces NAD+.
Breakdown of branched-chain amino acids involves transamination.
It starts with decarboxylation.
When defective, it results in maple syrup urine disease.

Question 47 of 110

Which of the following enzymes play an important role in the interconversion of glutamic acid to glutamine and back? (select all answers that are true)

Aromatic acid decarboxylase
Tyrosine transaminase
Glutamine synthetase
Deiodinase
Glutamine transaminase

Question 48 of 110

Which of the following is true regarding the synthesis of heme?

It begins with the incorporation of carbon dioxide.
The first step is catalyzed by aminolevulinic acid decarboxylase.
It begins with a cytoplasmic enzyme.
It starts with glycine and succinyl-CoA.
It begins with acetyl-CoA and glutamate.

Question 49 of 110

Which is true regarding the binding of the IRE-BP to the transferrin receptor mRNA?

It reduces the synthesis of the receptor.
It binds to the transferrin mRNA when iron concentrations are high.
It protects the 5’ end from nuclease degradation.
It allows nucleases to degrade the transferrin mRNA.
It occurs at the 3’ end.

Question 50 of 110

Which of the following is true regarding fetal hemoglobin?

It has a greater affinity for oxygen than myoglobin.
It is present until about 2 – 4 months after birth.
It binds 2,3 BPG tightly.
It replaces the α sub units with γ sub units.
Fetal hemoglobin is mostly in the T-state.

Question 51 of 110

Gilbert’s syndrome is caused by the deficiency of which of the following?

Stercobilin deficiency in the blood
Bilirubin deficiency in the blood
Biliverdin deficiency in the blood
Glucuronosyltransferase enzyme deficiency
Unconjugated bilirubin deficiency in the blood

Question 52 of 110

Which of the following glycolysis intermediate is the closest precursor to serine?

3-phosphoglycerate
2-phosphoglycerate
PEP
Pyruvate
DHAP

Question 53 of 110

Which of the following is true regarding phenylalanine?

It is a non-essential amino acid.
It can cause brain damage in high amounts
None of the answers are true.
An excess of phenylalanine hydroxylase causes phenylketonuria.
It is made from tyrosine.

Question 54 of 110

Which of the following is true regarding histidine metabolism?

Isoleucine inhibits this pathway.
It is a very simple pathway.
It overlaps with nucleotide metabolism.
It arises from tryptophan metabolism.
It involves 15 steps.

Question 55 of 110

Which pathway plays a critical role in maintaining the proper amounts of glutamic acid in the brain and getting rid of toxic ammonium ions at the same time?

Glucose-alanine cycle
Gluconeogenesis
Photosynthesis
ETC
Polymerization

Question 56 of 110

Which of the following is true regarding the synthesis of porphobilinogen?

Its formation requires decarboxylation.
Two glycines and two succinyl-CoAs would be required.
The enzyme is actually stimulated by heavy metals.
A ring structure is destroyed.
Porphobilinogen synthase is sensitive to cobalt ions.

Question 57 of 110

What happens to ferritin regulation at the low levels of iron inside the cell?

The IRE-BP binds to the iron and facilitates the binding of iron with the ferritin mRNA.
The IRE-BP binds to the iron and facilitates the synthesis of the ferritin protein.
The IRE-BP binds to the iron and halts the synthesis of ferritin protein.
The IRE-BP binds to the IRE of the ferritin mRNA and allows for the synthesis of the ferritin protein.
The IRE-BP binds to the IRE of the ferritin mRNA and blocks the synthesis of ferritin protein.

Question 58 of 110

Which of the following do not affect hemoglobin’s affinity for oxygen? (Check all that apply)

Carbon dioxide concentration
Na+ ion concentration
Nitrogen concentration
Proton concentration
Oxygen concentration

Question 59 of 110

The intestinal flora metabolizes the bilirubin diglucuronide to which of the following?

Bilirubin
Urobilinogen
Bilivardin
Heme
Glucuronic acid

Question 60 of 110

To which of the following amino acids is serine closely linked through folate metabolism?

Glycine
Arginine
Cysteine
None of the above
Alanine

Question 61 of 110

Which of the following is true regarding tyrosine?

It is essential only in the absence of phenylalanine.
It is important in chlorophyll.
All of the answers are true.
It is an important precursor of neurotransmitters.
A deficiency in one of the molecules derived from tyrosine causes Parkinson disease.

Question 62 of 110

Which of the following is true regarding amino acid catabolism?

Ketogenic amino acids are broken down into gluconeogenesis intermediates.
Glucogenic amino acids include those broken down into pyruvate and oxaloacetate.
Acetyl-CoA is a common intermediate for glucogenic amino acids.
Most amino acids are ketogenic.
Ketogenic amino acids break down to ketone bodies, such as acetone.

Question 63 of 110

Which of the following is NOT true for the urea cycle?

One urea molecule is produced per turn of the urea cycle.
The urea cycle occurs in the cytoplasm and mitochondria of the liver and kidney cells.
The net reaction for the urea cycle is 2NH3 + CO2 + 3ATP + H2O → CO(NH2)2 + 2ADP + 4Pi + AMP.
The urea cycle takes place in the neuronal cells to get rid of the toxic effect of ammonium ions produced during amino acid catabolism.
In the urea cycle, the feeder reaction synthesizes the carbamoylphosphate by incorporating ammonium and bicarbonate ions with the help of carbamoyl phosphate synthetase.

Question 64 of 110

Which of the following is true regarding the synthesis of hydroxymethylbilane?

None of the answers are true
All of the answers are true
Ammonia is released during this process.
Six glycines and six succinyl-CoAs would be required.
Increased production results in a type of porphyria.

Question 65 of 110

Which of the following is true regarding hemoglobin?

It is made up of two alpha subunits and one beta subunit.
It provides oxygen for less efficient ATP synthesis
It contains magnesium in the heme group.
It is important to animals with widely varying oxygen needs.
It can only carry one Oxygen molecule at a time.

Question 66 of 110

How does the proton concentration affect the affinity of hemoglobin for oxygen?

Protons change the amino acid sequence of hemoglobin, increasing its affinity for oxygen.
Protons bind to hemoglobin, increasing its affinity for oxygen.
Protons bind to hemoglobin, lowering the affinity for oxygen.
Protons allow more carbon dioxide in the blood, increasing hemoglobin's affinity for oxygen,
Protons change the amino acid sequence of hemoglobin, lowering its affinity for oxygen.

Question 67 of 110

Which of the following is true regarding thyroid hormones?

Thyroid hormones include thyroxine and triiodothyronine.
They are made inside of thyroid cells.
Thyromodulin is necessary for the synthesis of thyroid hormones.
They are derived from the breakdown of carbohydrates.
They are made from a precursor derived from glutamate called thyroglobulin.

Question 68 of 110

Which of the following is true regarding the movement of nitrogen-containing compounds in the body?

Ammonia levels in the brain are kept high.
Transamination is the most common mechanism.
Glutamate only donates ammonia.
Glutamine accepts ammonia from many sources.
In the lungs, ammonia is used for urea synthesis.

Question 69 of 110

Which of the following is not correctly matched regarding the reactions and enzymes in the urea cycle?

Citrulline + ATP + asparate → argininosuccinate + AMP + 2Pi — argininosuccinate synthetase
Argininosuccinate → arginine + fumarate — argininosuccinate lyase
Arginine + water → urea — arginase
Ammonium ion + bicarbonate ion → carbamoyl phosphate — ornithine transcarbamoylase
Carbamoylphosphate + ornithine → citrulline — ornithine transcarbamoylase

Question 70 of 110

Which of the following is true regarding uroporphyrinogen III?

None of the answers are true
It is the first cyclic intermediate in heme synthesis
Its synthesis requires input of water
All of the answers are true
It is in excess with congenital erythropoietic porphyria

Question 71 of 110

Which of the following is true regarding hemoglobin heme?

It has ferrous iron in the methemoglobin form.
It is comprised of amino acids.
Heme has four subunits.
Ferric iron is responsible for oxygen binding.
It binds oxygen in the Fe++ form.

Question 72 of 110

Which enzyme helps in the conversion of CO2 to carbonic acid during its transportation from tissues to the lungs?

Carbonic hydrase
Carbonic decarboxylase
Carbonic ligase
Carbonic anhydrase
Carbonic lyase

Question 73 of 110

The deficiency of which enzyme leads to phenylketonuria condition?

Phenylalanine hydroxylase
Phenylalanine synthase
Phenylalaninase
Phenylalanine transaminase
Phenylalanine kinase

Question 74 of 110

Which of the following is true regarding post-translational modification of amino acid side chains?

It involves phosphorylation of serine and threonine.
It involves carboxylation of arginine.
It results in glycosylation of proline.
It results in phosphorylation of glycine.
It results in the decarboxylation of tyrosine.

Question 75 of 110

Which of the following is true regarding argininosuccinate synthetase?

It catalyzes the fastest part of the reaction.
It uses a mechanism with a covalent bond to ADP
Its deficiency leads to tyrosinemia.
It requires glutamic acid
Expression of this enzyme is reduced by arginine.

Question 76 of 110

Which of the following is true regarding uroporphoryinogen III decarboxylase?

All of the answers are true
It is a methodical enzyme, working very slowly
None of the answers are true
It decarboxylates coproporphyrinogen III
It uses four carbon dioxide molecules

Question 77 of 110

Which of the following statements is not true?

Carbon dioxide competes with oxygen to bind to the heme unit of the hemoglobin.
Carbon monoxide competes with oxygen to bind with the Fe atom of the heme group in hemoglobin.
The binding of CO2 to the hemoglobin leads to a structural change in the hemoglobin and causes the release of O2 from the heme group.
The majority of transported CO2, to the lungs, is in the form of bicarbonate.
A histidine entity present above the heme group in the hemoglobin favors the binding of oxygen over CO.

Question 78 of 110

Which of the following amino acids is NOT part of the aspartate family?

Lysine
Threonine
Methionine
Asparagine
Cysteine

Question 79 of 110

Which of the following does not fall under the category of catecholamines?

L-DOPA
S-Adenosylmethionine
L-Dopamine
Norepinephrine
Epinephrine

Question 80 of 110

The branched-chain ketoaciduria (maple syrup urine disease) is caused due to the deficiency of which enzyme?

Threonine deaminase.
4-fumarylacetoacetase.
Homogentisate oxidase.
Tyrosine transaminase.
Branched-chain alpha-keto acid dehydrogenase complex (BCKDC).

Question 81 of 110

Which of the following is true regarding the synthesis of protoporphyrinogen IX?

None of the answers are true
Two molecules of coproporphyrinogen III are used during this process
The enzyme uses magnesium in catalysis
All of the answers are true
The enzyme catalyzing its formation is in the mitochondrion

Question 82 of 110

Which of the following is true regarding the cooperativity in hemoglobin?

The binding of the last oxygen is the least favorable oxygen binding.
The binding of oxygen turns hemoglobin into the T-state.
In the R-state, hemoglobin can carry three oxygen molecules.
The binding of the first oxygen is the least favorable oxygen binding.
Once the first globin changes to the R-state, all other globins change to the R-state.

Question 83 of 110

Fetal hemoglobin is composed of which of the following?

Two beta and two delta sub units
Two alpha and two gamma sub units
Two alpha and two delta sub units
Two beta and two gamma sub units
Two alpha and two beta sub units

Question 84 of 110

Transamination of glutamate and pyruvate could yield…?

…aspartate and glutamate.
…aspartate and alanine.
…α-ketoglutarate and alanine.
…valine and isoleucine.
…asparagine and alanine.

Question 85 of 110

Histidine amino acid synthesis is controlled by a feedback mechanism involving the interaction of which of the following?

ATP-phosphoribosyltransferase and histidine.
ATP-phosphoribosyltransferase and threonine.
Threonine deaminase and histidine.
Tyrosine transaminase and histidine.
Threonine deaminase and threonine.

Question 86 of 110

Which of the following is true regarding arginase?

It produces citrulline and urea from arginine.
It produces ornithine and citrulline from arginine.
It competes with nitric oxide synthase for arginine.
There is only one form of arginase in cells.
It is the most commonly deficient enzyme of the cycle.

Question 87 of 110

Which of the following is true regarding protoporphyrin IX?

It is formed in an oxidation reaction
It is a precursor of heme and chlorophyll
It is formed in a reaction catalyzed by an inner mitochondrial enzyme
All of the answers are true
None of the answers are true

Question 88 of 110

In what way does the myoglobin bind to oxygen?

To the same extent as hemoglobin
With lower affinity than hemoglobin
Irreversibly
With higher affinity than hemoglobin
Through a process call cooperativity

Question 89 of 110

Which of the following is true regarding heme catabolism?

Heme is first converted to bilirubin by heme oxygenase.
It occurs primarily in the liver.
It occurs primarily in the blood.
The first reaction is catalyzed by heme reductase.
Increased activity of heme oxygenase stimulates ferritin production.

Question 90 of 110

The hydroxylation of which amino acid is important for making strong collagen?

Lysine
Methionine
Threonine
Serine
Cysteine

Question 91 of 110

Which of the following are ketogenic amino acids?

Glycine and asparagine
Threonine and serine
Isoleucine and valine
Tyrosine and glutamate
Lysine and leucine

Question 92 of 110

Which of the following is true regarding nitrites?

They are oxidized to nitric oxide in oxygen abundance.
Most nitrites, in the human diet, come from cured meats.
They form the nitrosamines in stomach acid.
They are the body's only way to form nitrous oxide.
They oxidize hemoglobin's iron to Fe++.

Question 93 of 110

Which of the following molecules are affected severely by the attack of peroxynitrite?

Zinc and magnesium
Fatty acids and lipids
Starch and glycogen
Arginine and isovaline
Sidechains of cysteine and tyrosine in signaling proteins

Question 94 of 110

In the Bohr effect, which of the following is true of hemoglobin?

Protons have no effect on hemoglobin's shape.
It has a greater affinity for oxygen at higher pH.
It releases carbon dioxide when it binds to protons.
It lets go of oxygen as the proton concentration decreases.
It has a greater affinity for oxygen at lower pH.

Question 95 of 110

Which of the following is true regarding biliverdin reductase?

It takes on oxygen free radicals when biliverdin is converted to bilirubin.
It produces reactive oxygen species.
It recycles biliverdin to heme.
It recycles bilirubin to heme.
It catalyzes the conversion of biliverdin to bilirubin.

Question 96 of 110

Which part of amino acid gives it unique characteristics, structure, function, and chemistry?

Alpha amine
Carbonyl carbon
R group
Hydroxyl group
Alpha carbon

Question 97 of 110

The deficiency of which enzyme leads to homocystinuria?

Methionine adenosyltransferase
S-adenosyl methionine hydrolase
Cystathionase
Transmethylase
Cystathionine β-synthase

Question 98 of 110

Which of the following is not correctly associated regarding the defective amino acid catabolism?

Methylmalonic acidemia — methionine, threonine, isoleucine, and valine
Propionic academia — methionine, threonine, isoleucine, and valine
Homocystinuria — methionine
Alcaptonuria — alanine and threonine
Glycine encephalopathy — glycine

Question 99 of 110

Which of the following is true regarding nitrosamines?

They are produced from tertiary amines.
They are not carcinogenic in humans.
Baking food favors the production of nitrosamines.
Their formation is inhibited by Vitamin D.
They arise from a nitrosonium ion.

Question 100 of 110

Which of the following is true regarding heme?

All of the answers are true
It requires electronic rearrangement for its final form
It is formed as heme C and other hemes are made from it
It is formed by catalysis of ferrocatalase
None of the answers are true

Question 101 of 110

In the Bohr effect, hemoglobin releases which of the following?

Additional carbon dioxide in the presence of protons
Additional oxygen in the presence of oxygen
Additional oxygen near rapidly metabolizing tissues
Additional oxygen in the presence of oxygen and carbon dioxide
Additional carbon dioxide in the presence of oxygen.

Question 102 of 110

Which of the following is true regarding biliverdin reductase?

It acts as a protease.
It contains a threonine zipper.
It plays a role in glucose movement in the body.
Its only function is to convert biliverdin to bilirubin.
It is a serine-threonine-tyrosine kinase

Question 103 of 110

Essential amino acids are amino acids that must be what?

In the endoplasmic reticulum
Synthesized by an organism
In the ribosome
In the nucleus
In an organism’s diet

Question 104 of 110

Cystathionine is converted into cysteine and β-ketobutyrate by which enzyme?

S-adenosyl methionine hydrolase
Cystathionine β-synthase
Transmethylase
Methionine adenosyltransferase
Cystathionase

Question 105 of 110

Which of the following is true regarding the amino acids in the pyruvate family?

They are made from pyruvate by hydroxylation.
They are all derived from isoleucine.
They are not important in the glucose-alanine cycle.
They all have non-polar R groups.
They all have alanine as a precursor.

Question 106 of 110

Which of the following statements is NOT true regarding amino acid modifications?

Lysine amino acid commonly undergoes methylation, acetylation, and hydroxylation modification.
Asparagine is often modified by phosphorylation.
The myristoylation of glycine involves the addition of myristic acid to the glycine.
The disulfide bond formations between the two cysteine residues of a protein molecule give rise to the unstable structure.
Phosphotyrosine plays an important role in the cell signaling process.

Question 107 of 110

Which of the following is true with respect to reactive nitrogen species?

Nitric oxide combines with superoxide to make peroxynitrite.
They can oxidize metals, such as magnesium and potassium.
Nitrosation is a helpful process in the body.
They include the most reactive nitrogen molecule known as nitrous acid.
They have no effect on iron in the ferric state.

Question 108 of 110

Which of the following is true concerning porphyrias?

They can occur with the overproduction of enzymes that synthesize heme.
They are treated by going out into the sunlight.
They manifest with kidney disease.
They arise from deficiencies in heme synthesis enzymes.
They arise from the accumulation of heme.

Question 109 of 110

How do the high concentrations of iron regulate the transferrin receptor protein synthesis?

At high concentrations of iron, the binding of IRE-BP to transferrin receptor mRNA facilitates transferrin receptor protein synthesis
At high concentrations of iron, the binding of iron to IRE of transferrin receptor mRNA facilitates the synthesis of transferrin receptor protein
At high concentrations of iron, the binding of IRE-BP to iron facilitates the synthesis of transferrin receptor protein
At high concentrations of iron, the binding of IRE-BP to iron makes transferrin receptor mRNA susceptible to nuclease attack and prevent transferrin receptor protein synthesis
At high concentrations of iron, the binding of IRE-BP to iron and IRE of mRNA facilitates the synthesis of transferrin receptor protein

Question 110 of 110

Which of the following is true regarding the movement of bilirubin in the body?

Biliary obstruction results in darker feces and lighter urine.
Intestinal bacteria convert it to urobilinogen.
Urobilin gives feces its color.
Stercobilin gives urine its color.
Stercobilin can be recycled back to biliverdin to help with reactive oxygen species.

Amino Acid Biochemistry 2023

Amino Acid Biochemistry 2023

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