Category: Biochemistry Objective Questions

Biochemistry Multiple Choice Questions on “Nitrogen Excretion and the Urea Cycle”.

1. Urea production occurs almost exclusively in ___________
A. Kidneys
B. Liver
C. Blood
D. Urine
Answer: B
Clarification: Urea production occurs almost exclusively in the liver and is the fate of most of the ammonia channeled there. The urea passes into the blood stream and thus to the kidneys and is excreted into the urine.

2. Which is the first amino group entering into urea cycle?
A. carbamoyl phosphate
B. Ornithine
C. Cituilline
D. Argininosuccinate
Answer: A
Clarification: The carbamoyl phosphate, which functions as an activated carbamoyl group donor enters the urea cycle.

3. The first enzyme in the pathway carbamoyl phosphate synthase I, is allosterically activated by ___________
A. N-acetylglutamate
B. Acetyl coA
C. Glutamate
D. Carbamoyl phosphate
Answer: A
Clarification: The first enzyme in the pathway carbamoyl phosphate synthase I, is allosterically activated by N-acetylglutamate.

4. A second amino group is transferred to cituilline from ___________
A. Aspartate
B. Glutamate
C. Alanine
D. Guanine
Answer: A
Clarification: The second amino group enters from aspartate generated in mitochondria by transamination and transported into the cytosol.

5. Nitrogen atoms of urea produced in the urea cycle are derived from ___________
A. Ammonia and aspartic acid
B. Nitrate
C. Nitrite
D. Ammonia
Answer: A
Clarification: One amino group comes from ammonia and another comes from aspartate.

6. What are the products of urea cycle?
A. One molecule of urea, one molecule of ammonia, one molecule of ATP and one molecule of fumaric acid
B. One molecule of urea, one molecule of AMP, two molecules of ADP and one molecule of fumaric acid
C. One molecule of aspartic acid, one molecule of ammonia, one molecule of ATP and one molecule of fumaric acid
D. Two molecules of urea, two molecules of ammonia, one molecule of ATP and one molecule of fumaric acid
Answer: B
Clarification: Products of urea cycle are one molecule of urea, one molecule of AMP, two molecules of ADP and one molecule of fumaric acid.

7. The carbon atom source while producing urea in the urea cycle is ___________
A. CO₂
B. Glucose
C. Aspartic acid
D. Arginine
Answer: A
Clarification: CO₂ is the carbon atom source while producing urea in the urea cycle.

8. Which of the following is not an essential amino acid?
A. Glycine
B. Leucine
C. Methionine
D. Histidine
Answer: A
Clarification: Only Leucine, methionine and histidine are essential in this case.

9. Urea cycle converts ___________
A. Keto acids into amino acids
B. Amino acids into keto acids
C. Ammonia into a less toxic form
D. Ammonia into a more toxic form
Answer: C
Clarification: A less toxic ammonia form is produced by urea cycle.

10. What are the inputs to one cycle of urea cycle?
A. One molecule of CO₂, one molecule of ammonia, three molecules of ATP and one molecule of aspartic acid
B. One molecule of urea, one molecule of AMP, two molecules of ADP and one molecule of fumaric acid
C. One molecule of aspartic acid, one molecule of ammonia, one molecule of ATP and one molecule of fumaric acid
D. Two molecules of urea, two molecules of ammonia, one molecule of ATP and one molecule of fumaric acid
Answer: A
Clarification: One molecule of CO₂, one molecule of ammonia, three molecules of ATP and one molecule of aspartic acid are the inputs to one cycle of urea cycle.

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Biochemistry Multiple Choice Questions on “Regulation of Transcription by Steroid Hormones”.

1. How do steroid hormones produce their effects in cells?
A. By activating key enzymes in metabolic pathway
B. By binding to intracellular receptors and promoting transcription of specific genes
C. By promoting the degradation of specific m-RNAs
D. By activating translation of certain m-RNAs
Answer: B
Clarification: Steroid hormones produce their effects in cells by binding to intracellular receptors and promoting transcription of specific genes.

2. Which is an example of a positive regulator?
A. CAP
B. Lac 1 gene
C. Trp operon
D. Met operon
Answer: A
Clarification: Lac 1 gene, Trp operon and Met operon are negative regulators.

3. Which is an example of negative regulator?
A. CAP
B. Lac 1 gene
C. Nuclear receptors
D. Phosphorylated STAT proteins
Answer: B
Clarification: CAP, Nuclear receptors and Phosphorylated STAT proteins are positive regulators.

4. Steroid regulatory proteins mediate the act by binding at ___________
A. Zinc finger motif
B. Leucine zipper motif
C. Helix turn helix motif
D. Histone helix motif
Answer: A
Clarification: Steroid regulatory proteins mediate the act by binding at zinc finger motif.

5. Which out of the following statements is true about gene regulation in bacteria?
A. Repressor protein blocks transcription by binding to operator sequence
B. Activator proteins bind near promoters and increase the efficiency of transcription
C. Enhancers commonly regulate transcription
D. Genes with related functions are often grouped together and have a single start codon
Answer: A
Clarification: A repressor binds at operator element and regulates transcription negatively.

6. Steroid hormones receptor binds to _____________
A. Hormone response elements in m-RNA
B. Hormone response elements in DNA
C. Hormone response elements in proteins
D. Ribosomes to stimulate translation
Answer: B
Clarification: Hormone response elements are short sequence of DNA where steroid hormone receptors bind.

7. Mode of action of steroid hormones involve ______________
A. Stimulation of DNA replication
B. Stimulation of m-RNA transcription
C. Inhibition of protein synthesis
D. Secondary messenger
Answer: B
Clarification: Steroid hormones involve in the stimulation of m-RNA transcription, affecting the gene expression.

8. What is the drug antagonist of estrogen?
A. Tanoxifen
B. Metformin
C. Glucophage
D. Victoza
Answer: A
Clarification: Tanoxifen is an antagonist of estrogen.

9. Which drug is used to terminate early pregnancies?
A. RU486
B. Metformin
C. Glucophage
D. Victoza
Answer: A
Clarification: Metformin, Glucophage and victoza are the drugs to cure diabetes.

10. Plasma membrane protein predicted to have seen 7 transmembrane helices segment binds __________
A. Progesterone
B. Thyroid stimulating hormone
C. Insulin
D. Follicle stimulating hormone
Answer: A
Clarification: Progesterone hormone is a steroid hormone, can diffuse through cell membranes.

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Biochemistry Multiple Choice Questions on “From Genomes to Proteasomes”.

1. The study of the full complement of proteins expressed by a genome is called __________
A. Proteome
B. Proteomics
C. Genomics
D. Protein formation
Answer: B
Clarification: The full complement of proteins expressed by a genome is called proteome and the study of it is called proteomics.

2. The effects of protein on an entire organism is described in __________
A. Phenotypic function
B. Cellular function
C. Molecular function
D. Structural genomics
Answer: A
Clarification: Cellular function, it describes about the network of interactions engaged in by protein at cellular level.
Molecular function, it describes the precise biochemical activity of a protein.
Structural genomics, it includes sequencing of genomic DNA.

3. The network of interactions engaged in by protein at cellular level is described in __________
A. Phenotypic function
B. Cellular function
C. Molecular function
D. Structural genomics
Answer: B
Clarification: Molecular function, it describes the precise biochemical activity of a protein.
Structural genomics, it includes sequencing of genomic DNA.
Phenotypic function, it describes the effects of protein on an entire organism.

4. The precise biochemical activity of a protein is described in __________
A. Phenotypic function
B. Cellular function
C. Molecular function
D. Structural genomics
Answer: C
Clarification: Structural genomics, it includes sequencing of genomic DNA.
Phenotypic function, it describes the effects of protein on an entire organism.
Cellular function, it describes about the network of interactions engaged in by protein at cellular level.

5. Sequencing of genomic DNA is included in __________
A. Phenotypic function
B. Cellular function
C. Molecular function
D. Structural genomics
Answer: D
Clarification: Phenotypic function, it describes the effects of protein on an entire organism.
Cellular function, it describes about the network of interactions engaged in by protein at cellular level.
Molecular function, it describes the precise biochemical activity of a protein.

6. What is the goal of structural proteomics project?
A. To crystallize and determine the structure of as many proteins as possible, in many cases with little or no existing information about protein function
B. To identify and sequence of all the genes present in the human body
C. To introduce new genes to human beings
D. To remove disease causing genes from humans
Answer: A
Clarification: Options b, c, d comes under the goals of human genomic project.

7. Conserved gene order can be termed as __________
A. Ortholog
B. Synteny
C. Paralog
D. Microarray
Answer: B
Clarification: Genes of different species but possessing a clear sequence and functional relationship to each other are orthologs.
Genes of same species, similarly related to each other are paralogs.
Collections of microscopic DNA spots attached to solid surface are DNA microarrays.

8. Genes of different species but possessing a clear sequence and functional relationship to each other are __________
A. Ortholog
B. Synteny
C. Paralog
D. Microarray
Answer: A
Clarification: Collections of microscopic DNA spots attached to solid surface are DNA microarrays.
Genes of same species, similarly related to each other are paralogs.
Synteny is a conserved gene order.

9. Genes of same species, similarly related to each other are __________
A. Ortholog
B. Synteny
C. Paralog
D. Microarray
Answer: C
Clarification: Genes of different species but possessing a clear sequence and functional relationship to each other are orthologs.
Synteny is a conserved gene order.
Collections of microscopic DNA spots attached to solid surface are DNA microarrays.

10. Collection of microscopic DNA spots attached to the solid surface are __________
A. Ortholog
B. Synteny
C. Paralog
D. Microarray
Answer: D
Clarification: Genes of different species but possessing a clear sequence and functional relationship to each other are orthologs. Genes of same species, similarly related to each other are paralogs. Synteny is a conserved gene order.

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Biochemistry Interview Questions and Answers for freshers focuses on “Reversible Binding of a Protein to a Ligand: Oxygen-Binding Proteins”.

1. Which of the following is false?
A. Heme consists of a complex organic ring structure, protoporphyrin
B. Protoporphyrin is bound to a single iron atom in its Fe⁺³ state
C. Iron atom has 6 coordination bonds
D. Heme is found in a number of oxygen transporting proteins
Answer: B
Clarification: Protoporphyrin is bound to a single iron atom in its Fe⁺² state.

2. Myoglobin is particularly abundant in ________
A. Nerves
B. Muscles
C. Blood cells
D. Skin
Answer: B
Clarification: As a transport protein, it facilitates O₂ diffusion in muscle.

3. His⁹³ is also called ________
A. His F8
B. His F7
C. His F6
D. His F5
Answer: A
Clarification: His⁹³, the 93^rd amino acid residue from the amino-terminal end of the myoglobin polypeptide sequence is also called His F8, the 8th residue in α helix F.

4. Which of the following is a correct relation?
A. K_a [L] = ^[PL] ⁄ _[P]
B. K_a [L] = ^[P] ⁄ _[PL]
C. K_a [L] = [PL] × [P]
D. K_a [PL] = ^[L] ⁄ _[P]
Answer: A
Clarification: The term K_a is an association constant
K_a [L] = ^[PL] ⁄ _{[P] [L]}.

5. Which of the following is a correct relation?
A. K_d [L] = ^[PL] ⁄ _[P]
B. K_d [L] = ^[P] ⁄ _[PL]
C. K_d [L] = [PL] × [P]
D. K_d [PL] = ^[L] ⁄ _[P]
Answer: A
Clarification: The term K_d is a dissociation constant
K_a [L] = ^{[P] [L]} ⁄ _[PL].

6. Myoglobin binding of O₂ depends on ___________
A. Hemoglobin concentration
B. O₂ concentration and affinity of myoglobin for O₂
C. K_a
D. K_d
Answer: B
Clarification: Myoglobin binding of O₂ depends on pO₂ and its affinity for O₂.

7. In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as ___________
A. Hyperbolic
B. Linear with a negative slope
C. Linear with a positive slope
D. Parabolic
Answer: A
Clarification: The equation θ=(pO₂)/(pO₂ +P₅0) is of the form y = x/(x+z) which describes hyperbola.

8. Myoglobin and the subunits of hemoglobin have ___________
A. Very different primary and tertiary structures
B. Very similar primary and tertiary structures
C. Very similar primary structures, but different tertiary structures
D. Very similar tertiary structures, but different primary structures
Answer: D
Clarification: Hemoglobin is a tetramer and myoglobin is a monomer.

9. The interactions of ligands with proteins are ___________
A. Relatively nonspecific
B. Relatively rare in biological systems
C. Usually irreversible
D. Usually transient
Answer: D
Clarification: The interactions of ligands with proteins are reversible and transient.

10. When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe²⁺ are occupied by___________
A. One O atom and one amino acid atom
B. One O₂ molecule and one amino acid atom
C. One O₂ molecule and one heme atom
D. Two O atoms
Answer: B
Clarification: The two coordination bonds to Fe²⁺ perpendicular to the porphyrin ring system. One of these bonds is occupied by a Hys residue and the other bond by O₂.

of Biochemistry for Interviews, .

Biochemistry Multiple Choice Questions on “Metabolic Fates of Amino Groups”.

1. Glutamate is metabolically converted to α-ketoglutarate and NH₄⁺ by a process ___________
A. Oxidative deamination
B. Transamination
C. Reductive deamination
D. Deamination
Answer: A
Clarification: Glutamate is metabolically converted to α-ketoglutarate and NH₄⁺ by a process oxidative deamination catalyzed by L-glutamate dehydrogenase.

2. Free ammonia combined with glutamate to yield glutamine by the action of ___________
A. Glutaminase
B. Glutamine synthase
C. Glutamate dehydrogenase
D. Amino transferase
Answer: B
Clarification: The free ammonia is combined with glutamate to yield glutamine by the action of glutamine synthase.

3. Pyridoxal phosphate and its aminate form, pyridoxamine phosphate are tightly bound coenzymes of ___________
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: All aminotransferases have pyridoxal phosphate (PLP) as cofactor.

4. What is the necessary coenzyme for transamination reactions?
A. Pyridoxal phosphate
B. Thiamine pyrophosphate
C. NAD
D. Coenzyme A
Answer: A
Clarification: Pyridoxal phosphate functions as an intermediate carrier of amino groups at the active site of amino transferases.

5. Which is the first step in the catabolism of most L-amino acids once they have reached the liver is promoted?
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: The first step in the catabolism of most L-amino acids once they have reached the liver is removal of the α-amino groups promoted by enzymes called amino transferases or trasaminases.

6. The combined action of aminotransferase and glutamate dehydrogenase is referred as ___________
A. Oxidative deamination
B. Transamination
C. Reductive deamination
D. Transdeamination
Answer: D
Clarification: The combined action of aminotransferase and glutamate dehydrogenase is referred as transdeamination.

7. Glutamine is converted to glutamate and NH₄⁺ by ___________
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: B
Clarification: In the tissues of intestine, liver and kidneys, the amide nitrogen is released as ammonium ion in the mitochondria, where glutaminase converts glutamine to glutamate and NH₄⁺.

8. Which of the following operates at an important intersection of carbon and nitrogen metabolism?
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: D
Clarification: Glutamate dehydrogenase operates at an important intersection of carbon and nitrogen metabolism.

9. Trypsinogen is converted to its active state by ___________
A. Enteropeptidase
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: Trypsinogen is converted to its active state by enteropeptidase, a proteolytic enzyme secreted by intestinal cells.

10. Which of the following hydrolyzes successive amino-terminal residues from short peptides?
A. Aminopeptidase
B. Enteropeptidase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: Aminopeptidase hydrolyzes successive amino-terminal residues from short peptides.

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