Category: Biochemistry Objective Questions

Biochemistry Multiple Choice Questions on “Protein Interactions Modulated by Chemical Energy: Actin, Myosin and Molecular Motors”.

1. Light band has which of the following filament protein?
A. Actin
B. Myosin
C. Actin and myosin
D. Tubulin
Answer: A
Clarification: Light band has actin because it is a part of the thin filament.

2. Contractile protein of a muscle is __________
A. Troponin
B. Myosin
C. Tubulin
D. Tropomyosin
Answer: B
Clarification: Both actin and myosin are the two contractile proteins.

3. Which of the following contractile protein of skeletal muscle involve in ATPase activity?
A. Troponin
B. Myosin
C. Tubulin
D. Tropomyosin
Answer: B
Clarification: ATPase activity involves the conversion of ATP to ADP which releases energy. Myosin involves in such type of activity.

4. The cross bridges involved in muscle contraction are located on the __________
A. Myosin myofilaments
B. Actin myofilaments
C. Tropomyosin
D. Dystrophin
Answer: A
Clarification: The globular head of a myosin that projects from myosin filament is a cross bridge.

5. The contractile unit consisting of bundles of thick filaments interleaved at either end with those of thin filaments is?
A. Myofibril
B. Cross bridges
C. Z band
D. Sarcomere
Answer: D
Clarification: Sarcomere is the contractile unit consisting of bundles of thick filaments interleaved at either end with those of thin filaments.

6. Sarcomere is a part between __________
A. 2 I bands
B. 2 Z bands
C. 2 A bands
D. 2 H bands
Answer: B
Clarification: Z lines are formed between adjacent sarcomeres.

7. Which of the following is the smallest division?
A. Actin
B. Fiber
C. Fibril
D. Filament
Answer: A
Clarification: Actin, which is the part of the thin filament, is the smallest division in that group.

8. Which of the following is false?
A. Actin is a thin filament
B. Myosin is a thick filament
C. The band in a myofibril is an area of thin filament
D. Functional unit of muscle is sarcomere
Answer: C
Clarification: The band in a myofibril is an area of thick filament.

9. The connective tissue that surrounds individual fibers is __________
A. Fascia
B. Epimysium
C. Endomysium
D. Perimysium
Answer: C
Clarification: Endomysium is present in between one muscle cell and other.

10. Which of the following is an invagination of the muscle cell’s sarcolemma?
A. Cisternae
B. Microtubules
C. T tubules
D. Sarcoplasmic reticula
Answer: C
Clarification: Transverse tubules are the invaginations of the muscle cell’s sarcolemma.

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Biochemistry Multiple Choice Questions on “Pathways of Amino Acid Degradation”.

1. Which of the following amino acids are exclusively ketogenic?
A. Leucine
B. Asparagine
C. Threonine
D. Proline

Answer: A
Clarification: Only two amino acids, leucine and lysine are exclusively ketogenic.

2. Which of the following are exclusively glucogenic?
A. Arginine
B. Leucine
C. Lysine
D. Threonine

Answer: A
Clarification: Leucine and lysine are exclusively ketogenic. Threonine is both ketogenic and glucogenic.

3. Which of the following yields acetyl co-A via aceto-acetyl co-A?
A. Leucine
B. Isoleucine
C. Threonine
D. Alanine

Answer: A
Clarification: Leucine, lysine, phenylalanine and tryptophan yield acetyl co-A via aceto-acetyl co-A.

4. Which of the following yields acetyl coA directly?
A. Phenylalanine
B. Isoleucine
C. Lysine
D. Alanine

Answer: B
Clarification: Isoleucine, leucine, threonine and tryptophan yield acetyl coA directly.

5. Which of the following produces pyruvate?
A. Leucine
B. Isoleucine
C. Lysine
D. Alanine

Answer: D
Clarification: The amino acids producing pyruvate are alanine, cysteine, glycine, serine, threonine and tryptophan.

6. Which of the following produces α-ketoglutarate?
A. Leucine
B. Threonine
C. Methionine
D. Proline

Answer: D
Clarification: Arginine, glutamate, glutamine, histidine and proline produce α-ketoglutarate.

7. Which of the following produce succinyl co-A?
A. Leucine
B. Isoleucine
C. Arginine
D. Alanine

Answer: B
Clarification: Isoleucine, methionine, threonine and valine produce succinyl co-A.

8. Fumarate is produced from four carbon atoms of _________
A. Tyrosine
B. Isoleucine
C. Threonine
D. Alanine

Answer: A
Clarification: Four carbon atoms of phenylalanine and tyrosine give rise to fumarate.

9. Which of the following produces oxaloacetate?
A. Aspartate
B. Isoleucine
C. Threonine
D. Alanine

Answer: A
Clarification: Asparagine and aspartate produce oxaloacetate.

10. The branched chain amino acid is not _________
A. Leucine
B. Isoleucine
C. Valine
D. Alanine

Answer: D
Clarification: Isoleucine, leucine and valine are the branched chain amino acids.

Biochemistry Multiple Choice Questions on “Regulation of the Cell Cycle by Protein Kinases”.

1. Which of the following statements regarding cyclin-dependent protein kinase is not correct?
A. Their activity is regulated by cyclins
B. They can alter the activity of proteins involve in the progression of cells through cell cycle
C. Their activity fluctuates during cell cycle
D. Each type of cell contains one specific form
e) Their activity is regulated by changes in gene expression, protein phosphorylation and proteolysis
Answer: C
Clarification: They remain constant throughout cell cycle.

2. Which of the following statements regarding cyclins is not correct?
A. They can become linked to ubiquitin
B. They catalyze the phosphorylation of protein
C. They contain a specific amino acid sequence that target them for proteolysis
D. They are activated and degraded during cell cycle
Answer: D
Clarification: They activate cdk enzymes.

3. What is Ubiquitin?
A. Protein kinase
B. Protease
C. Component of the electron transport system
D. Protein that tags another protein for proteolysis
Answer: D
Clarification: Ubiquitin binds to a substrate protein resulting in their degradation.

4. Cdk2/cyclinE functions in ____________
A. G₂/M transition
B. G₂
C. M
D. G₁/S transition
Answer: D
Clarification: Cdk1/cyclinB functions in M phase Cdk2/cyclinA functions in S phase, G₂ phase.

5. In which phase of cell cycle is DNA replicated?
A. G₁ phase
B. S phase
C. G₂ phase
D. M phase
Answer: B
Clarification: During the S phase, DNA replication takes place.

6. Cyclin dependent kinases which control progression through cell cycle checkpoints are totally activated by which of the following?
A. Binding to cyclin, plus phosphorylation by a Cdk activating protein kinase
B. Binding to cyclins
C. Phosphorylation by Cdk activating protein kinase
D. Phosphorylation by a tyrosine kinase
Answer: A
Clarification: Cyclin dependent kinases are totally activated by binding to cyclin and phosphorylation by a Cdk activating protein kinase.

7. At the end of each phase of cell cycle cyclins activating Cdks in that phase are inactivated irreversibly by _____________
A. Multiple phosphorylations
B. De-phosphorylation
C. Ubiquitinylation
D. Destabilizing by proteolysis in a proteosome
Answer: D
Clarification: At the end of each phase of cell cycle, cyclins are inactivated irreversibly by destabilizing by proteolysis in a proteasome.

8. At which cell cycle checkpoint, cell cycle is halted if cell’s DNA is damaged?
A. G₁ – S
B. S – G₂
C. G₂ – M
D. G₀ – G₁
Answer: A
Clarification: During G₁ phase cell grows and during S phase DNA replicates. So there must be a checkpoint between these two phases to check if there is a damage in DNA.

9. Which of the following occurs in meiosis but not in mitosis?
A. Attachment of spindle fibers to kinetochore
B. Replication of DNA prior to start of cell division
C. Separation of sister chromatids at anaphase
D. Pairing of homologous chromosomes at metaphase plate
Answer: D
Clarification: Pairing of homologous chromosomes at metaphase plate does not occur in mitosis.

10. Passage of a cell through stages of cell cycle is controlled by a protein kinase that phosphorylates many different proteins at appropriate times.
A. Cdk activating kinase
B. Cyclin-dependent kinase
C. Cyclins
D. Tyrosine kinase
Answer: B
Clarification: Passage of a cell through stages of cell cycle is controlled by Cdk.

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Biochemistry Quiz focuses on “Genome Alterations and New Products of Biotechnology”.

1. Rauolfia serpentine, to save this plant under the threat of extinction, which of the following techniques is useful?
A. Genetic engineering
B. In vitro culture
C. DNA fingerprinting
D. Hybridoma technology
Answer: B
Clarification: In vitro culture is useful in saving this plant from extinction.

2. Transgenic organisms are generally __________
A. Extinct organisms
B. Naturally occurring and endemic
C. Produced by traditional plant breeding technique
D. Produced by gene transfer technology
Answer: D
Clarification: Transgenic technology, also known as genetic engineering involves the transfer of genes from one species to another.

3. Dolly, the first animal produced by cloning is a __________
A. Cow
B. Sheep
C. Rat
D. Dog
Answer: B
Clarification: Dolly is a female domestic sheep that was cloned using nuclear transfer process from an adult somatic cell.

4. Gene therapy is a technique preferred to cure inherited diseases by __________
A. Repairing the faulty gene
B. Introducing the correct copy of the gene
C. Adding new cells to the body
D. PCR
Answer: B
Clarification: By inserting a gene in place of defective ones in order to correct genetic disorders is included in gene therapy.

5. Glucose is added to the tissue culture media as a/an __________
A. Carbon source
B. Growth regulator
C. Solidifying agent
D. Antibiotic
Answer: A
Clarification: Energy is derived from glucose.

6. Explant can be a __________
A. Cut part of the plant used in tissue culture
B. Plant extract used in tissue culture
C. Source of growth regulators added to media
D. Solidifying agent
Answer: A
Clarification: Explant is a piece of plant or animal tissue placed in a culture medium.

7. Meristem culture helps in developing which of the following?
A. Tall plants
B. Disease resistant plants
C. Virus free plants
D. Hybrid plants
Answer: C
Clarification: Apical meristem from the infected plant is collected and cultivated in appropriate media so that new, complete and virus-free plants develop.

8. Which of the following is used to transfer genes in plants?
A. Ti plasmid
B. pBR 322
C. EcorI
D. pUC 18
Answer: A
Clarification: Ti plasmid of agrobacterium is used to transfer genes in plants.

9. Which of the following bacterium is used for gene transfer in plants?
A. Agrobacterium
B. Azatobacter
C. Rhizobium
D. Ecoli
Answer: A
Clarification: Agrobacterium is the only bacterium capable of transferring genes to plants.

10. Production of a large number of genetically similar plants through plant tissue culture is called __________
A. Recombinant DNA technology
B. Gene therapy
C. Micro propagation
D. Hybridoma technology
Answer: C
Clarification: Micro propagation is the practice of producing a large number of genetically similar plants through plant tissue culture.

of Biochemistry for Quizzes, .

Biochemistry Questions and Answers for Experienced people focuses on “Complementary Interactions Between Proteins and Ligands: The Immune System and Immunoglobulins”.

1. Which of the following is not the function of helper T cells is ____________
A. Produce soluble signaling proteins called cytokines, which include the interleukins
B. They help activate cytotoxic T cells to kill infected target cells
C. They help activate B cells to secrete antibodies and macrophages to destroy ingested microbes
D. They recognize and bind extracellular ligands
Answer: D
Clarification: The function of T_H cells is to interact with macrophages and secrete cytokines that stimulate T_C, T_H and B cells to proliferate.

2. Which of the following is a function of Macrophages?
A. Ingest large particles and cells by phagocytes
B. Produce and secrete antibodies
C. Interact with infected host cells through receptors on T-cell surface
D. Interact with macrophages and secrete cytokines
Answer: A
Clarification: The remaining are the functions of B cells, T_C and T_H cells respectively.

3. Which of the following is a function of B lymphocytes?
A. Ingest large particles and cells by phagocytes
B. Produce and secrete antibodies
C. Interact with infected host cells through receptors on T-cell surface
D. Interact with macrophages and secrete cytokines
Answer: B
Clarification: The remaining are the functions of macrophages, T_C and T_H cells respectively.

4. Which of the following is a function of T lymphocytes?
A. Ingest large particles and cells by phagocytes
B. Produce and secrete antibodies
C. Interact with infected host cells through receptors on T-cell surface
D. Interact with macrophages and secrete cytokines
Answer: C
Clarification: The remaining are the functions of macrophages, B cells and T_C respectively.

5. The most abundant immunoglobulin is ____________
A. IgA
B. IgE
C. IgG
D. IgM
Answer: C
Clarification: IgG is the most abundant antibody found in all body fluids.

6. Which of the following is the largest immunoglobulin?
A. IgA
B. IgE
C. IgG
D. IgM
Answer: D
Clarification: IgM is the largest pentameric type of antibody in the human circulatory system.

7. The antibody present in secretions like tears and saliva is ____________
A. IgA
B. IgE
C. IgG
D. IgM
Answer: A
Clarification: Secretory IgA is the main antibody present in mucous secretions and other secretions like tears and saliva.

8. Which of the following antibody first reaches the site of infection?
A. IgA
B. IgE
C. IgG
D. IgM
Answer: D
Clarification: IgM which is produced by B cells appears in response to the initial exposure to antigen.

9. Where do T-lymphocytes develop into fully competent but not activated T-cells?
A. The thymus gland
B. The lymph nodes
C. The thyroid gland
D. The bone marrow
Answer: A
Clarification: T cells are called so because they mature in the thymus gland.

10. Which of the following is true?
A. Most of the antibodies recognize small organic molecules
B. Most of the antibodies recognize proteins
C. Monoclonal antibodies produced in the laboratory lack the constant regions of IgG
D. IgM is a pentamer with 10 antigen binding sites
Answer: B
Clarification: Antibodies can recognize proteins like antigens.

11. IgG consists of ____________
A. A light chain and two heavy chains joined by a disulfide bond
B. Two light chains and a heavy chain joined by a disulfide bond
C. Two light chains and two heavy chains joined by a disulfide bond
D. Two light chains and two heavy chains joined by hydrogen bond
Answer: C
Clarification: IgG consists of 2 subunits including 2 heavy chains and 2 light chains.

12. Which of the following is a true statement?
A. IgG is involved in primary immune response
B. IgM is involved in primary immune response
C. IgG is involved only in secondary immune response
D. IgG and IgM both are involved in primary immune response
Answer: D
Clarification: IgG and IgM are involved in primary immune response.

13. The primary antibody of exocrine secretions is ____________
A. IgA
B. IgE
C. IgG
D. IgM
Answer: A
Clarification: IgA occurs in exocrine secretions and defends against bacteria cells and viruses.

14. Which of the following is not a feature of secondary immune respone to an antigen when compared to the first immune response to the same antigen?
A. Antibody is generated without T-cell help
B. Antibody is generated fast
C. Antibody produced has greater affinity for the antigen
D. Much antibody is produced
Answer: A
Clarification: The features of the secondary immune response are:
More antibodies are generated and the generation is fast.
Antibody produced has a greater affinity for the antigen.

15. Which of the following presents antigenic peptide to T-cells in order to initiate an adaptive immune response?
A. Plasma cell
B. Dendrite cell
C. Neutrophil
D. Epithelial cell
Answer: A
Clarification: Plasma cell is a fully differentiated B cell that produces antibody.

of Biochemistry for Experienced people, .

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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