Category: Biochemistry Objective Questions

Biochemistry Interview Questions and Answers for Experienced people focuses on “DNA Cloning: The Basics – 2”.

1. Generally, YAC contains how many elements?
A. 1
B. 2
C. 3
D. 4
Answer: D
Clarification: Ori, selectable markers X and Y, 2 telomeres and 1 centromere.

2. Which of the following endonuclease removes a length of DNA between two telomere sequences?
A. EcoR1
B. EcoR2
C. BamHI
D. HindIII
Answer: C
Clarification: BamHI removes a length of DNA between two telomere sequences.

3. In hybridization method, which of the following is pressed onto agar?
A. Silicon paper
B. Nitrocellulose paper
C. Filter paper
D. PVDF
Answer: B
Clarification: Nitrocellulose membrane has high binding capacity for proteins.

4. Which of the following temperature best suits for the growth and multiplication of transformed cells?
A. 35°C
B. 36°C
C. 37°C
D. 30°C
Answer: C
Clarification: (37-43) °C is the temperature range preferred for the growth and multiplication of transformed cells.

5. Which of the following is a DNA element that instructs RNA polymerase where to bind on DNA?
A. Operator
B. Promoter
C. Enhancer
D. Hormone response element
Answer: B
Clarification: Promoter instructs RNA pol where to bind on DNA.

6. Site directed mutagenesis facilitated research on __________
A. Carbohydrates
B. Proteins
C. Lipids
D. Fats
Answer: B
Clarification: Site directed mutagenesis changes the amino acid sequence by altering DNA sequence of cloned gene. It facilitates research on proteins.

7. Recombinant DNA molecule is produced by ligating __________
A. Two DNA segments
B. Two m-RNA molecules
C. One m-RNA with one t-RNA
D. One m-RNA with DNA segment
Answer: A
Clarification: For the construction of recombinant DNA molecule, two DNA segments are ligated.

8. Arrange the following steps involved in Gene cloning in the correct order.

i) Isolation of desired gene
ii) Insertion of isolated gene to the vector
iii) Introduction of recombinant vector to the host
iv) Expression of recombinant gene in host
v) Extraction of recombinant gene product

A. i, ii, iii, iv, v
B. v, iv, iii, ii, i
C. i, iii, ii, iv, v
D. iv, v, ii, i, iii
Answer: A
Clarification: i) Isolation of desired gene.
ii) Insertion of isolated gene to the vector.
iii) Introduction of recombinant vector to the host.
iv)Expression of recombinant gene in host.
v) Extraction of recombinant gene product.

9. Where does a restriction endonuclease cuts DNA?
A. Ligation site
B. Recognition sequence
C. Ori
D. Replication site
Answer: B
Clarification: Restriction enzymes cut DNA at specific sites called recognition sites.

10. Which of the following statements is true about a vector?
A. Plasmids, phages can be used as vectors
B. All vectors are plasmids
C. Cyanobacteria can also be used as vectors
D. Fungi can also be used as vectors
Answer: A
Clarification: Plasmids and phages can be used as vectors.

11. Which of the following is true about plasmids?
A. They are present in all organisms
B. They are present in bacteria only
C. They are present in bacteria and phages
D. They are present in plants and animals
Answer: C
Clarification: Plasmids cannot be found in animal cells. They are found only in bacteria and phages.

12. DNA Ligase, used in recombinant DNA technology is obtained from _______________
A. E.coli only
B. E.coli and also Ligase encoded by T4 phage
C. Saccharomyces
D. Retroviruses
Answer: B
Clarification: Ligase obtained from Ecoli and T4 DNA ligase is used in recombinant DNA technology.

13. What is the main aim of human genome project?
A. To identify and sequence of all the genes present in the human body
B. To introduce new genes to human beings
C. To remove disease causing genes from humans
D. To improve techniques of finger printing
Answer: A
Clarification: The main aim of human genome project is to identify and sequence of all the genes present in the human body.

14. The work ‘Hybridization’ in DNA finger printing means ____________
A. Pairing between the nucleotides of DNA sample with probe
B. Pairing between the nucleotides of DNA and mRNA
C. Pairing between the nucleotides of probe with mRNA
D. Pairing between the nucleosides with mRNA
Answer: A
Clarification: Hybridization involves annealing of DNA segment with its probe.

15. Agar is extracted from ____________
A. Fungi
B. Bacteria
C. Algae
D. Virus
Answer: C
Clarification: Agar is obtained from an alga.

of Biochemistry for Interviews, .

Biochemistry Multiple Choice Questions on “Protein Secondary Structure”.

1. Which of the following does not affect the stability of an α-helix?
A. Electrostatic repulsion
B. Bulkiness
C. Interaction between R groups spaced three residues apart
D. Occurrence of alanine and glycine residues
Answer: D
Clarification: The occurrence of Proline and Glycine residues affect the stability of an α-helix.

2. Which of the following is not true about secondary protein structure?
A. The hydrophilic/hydrophobic character of amino acid residues is important to secondary structure
B. The ability of peptide bonds to form intramolecular hydrogen bonds is important to secondary structure
C. The alpha helix, beta pleated sheet and beta turns are examples of protein secondary structure
D. The steric influence of amino acid residues is important to secondary structure
Answer: A
Clarification: The hydrophilic/hydrophobic character of amino acid residues is important to protein tertiary structure rather than to secondary structure. In secondary structure, it is the steric size of the residues that is important and residues are positioned to minimize interactions between each other and the peptide chain.

3. β-pleated sheets are the examples of _________
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Quaternary structure
Answer: B
Clarification: Secondary structure of proteins is of two forms α-helix and β-pleated structures.

4. A coiled peptide chain held in place by hydrogen bonding between peptide bonds in the same chain is?
A. Primary structure
B. α-helix
C. β-pleated sheets
D. Tertiary structure
Answer: B
Clarification: A coiled peptide chain held in place by hydrogen bonding between peptide bonds in the same chain is α helix.

5. A structure that has hydrogen bonds between polypeptide chains arranged side by side is?
A. Primary structure
B. α-helix
C. β-pleated sheets
D. Tertiary structure
Answer: C
Clarification: A structure that has hydrogen bonds between polypeptide chains arranged side by side is β-pleated sheets.

6. Which of the following are known as helix breakers?
A. Proline and glycine
B. Isoleucine and leucine
C. Valine
D. Threonine
Answer: A
Clarification: Proline and glycine are known as helix breakers as they disrupt the regularity of the alpha helical backbone conformation.

7. Which of the following is false about NMR spectroscopy?
A. NMR is an abbreviated form of Nuclear Magnetic Resonance
B. The intramolecular magnetic field around an atom in a molecule changes the resonance frequency giving structural information about the atom
C. The intermolecular magnetic field around an atom in a molecule changes the resonance frequency giving structural information about the atom
D. It is a technique that exploits magnetic properties of atomic nuclei
Answer: C
Clarification: The intramolecular magnetic field around an atom in a molecule changes the resonance frequency giving structural information about the atom.

8. Which of the statements is false about multiple sequence alignment?
A. Both protein and nucleic acid secondary structures can be used
B. More useful in RNA
C. These alignments can be made more accurate by the inclusion of secondary structure information
D. A significant increase in accuracy
Answer: B
Clarification: Less useful in RNA. This is because base pairing is highly conserved than sequence.

9. Secondary structure is defined by _________
A. Hydrogen bonding
B. Vander Waals forces
C. Covalent bonding
D. Ionic bonding
Answer: A
Clarification: Hydrogen bonding is present between the amine hydrogen and carbonyl oxygen atoms in the peptide backbone.

10. Which of the following is a false statement?
A. α-Keratin is α helical
B. Collagen is α helical
C. Hemoglobin has a quaternary structure
D. α-Keratin is β pleated structure
Answer: D
Clarification: Fibrous structural protein, α-Keratin is α helical.

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Biochemistry Multiple Choice Questions on “Biosynthesis of Triacylglycerols”.

1. Which of the following is not true regarding the synthesis of triacylglycerol in adipose tissue?
A. Phosphatidate is hydrolyzed
B. Glycerol 3-phosphate dehydrogenase plays an important role
C. Glycerol kinase plays an important role
D. It is synthesized from dihydroxyacetone phosphate
Answer: C
Clarification: The enzyme glycerol kinase has no role to play in the synthesis of triacylglycerol.

2. Hydrolysis of phosphatidic acid by phosphatidic acid phosphatase yields ___________
A. 1, 2-diacylglycerol
B. 1, 3-diacylglycerol
C. 1, 4-diacylglycerol
D. 1, 5-diacylglycerol
Answer: A
Clarification: In the pathway to triacylglycerols, phosphatidic acid is hydrolyzed by phosphatidic acid phosphatase to form a 1, 2-diacylglycerol.

3. In animal tissues, triacylglycerols and glycerophospholipids share two precursors ___________
A. Fatty acyl co-A and L-glycerol 3-phosphate
B. L-glycerol 3-phosphate and L-glycerol 2-phosphate
C. Diacylglycerol 3-phosphate and L-glycerol 3-phosphate
D. L-glycerol 3-phosphate and diacylglycerol 2-phosphate
Answer: A
Clarification: In animal tissues, triacylglycerols and glycerophospholipids share two precursors fatty acyl co-A and L-glycerol 3-phosphate.

4. Which of the following is more commonly called phosphatidic acid?
A. Diacylglycerol 3-phosphate
B. Fatty acyl co-A
C. L-glycerol 3-phosphate
D. L-glycerol 2-phosphate
Answer: A
Clarification: Diacylglycerol 3-phosphate is more commonly called phosphatidic acid or phosphatidate.

5. Where does the triacylglycerol form?
A. Liver
B. Kidneys
C. Adipose tissue
D. Heart
Answer: A
Clarification: Triacylglycerol formed in the liver is transported in the blood back to adipose tissue.

6. In adipose tissue, glyceroneogenesis couples with ___________
A. Reesterification
B. Esterification
C. Glycolysis
D. Phosphorylation
Answer: A
Clarification: In adipose tissue, glyceroneogenesis coupled with reesterification of free fatty acids controls the rate of fatty acid release to the blood.

7. Which of the following class of drugs reduce the levels of fatty acids circulating in the blood?
A. Thiazolidinediones
B. Amphetamines
C. Cathinones
D. Synthetic cannabinoids
Answer: A
Clarification: Thiazolidinediones reduce the levels of fatty acids circulating in the blood and increase sensitivity to insulin.

8. The higher activity of which of the following enzymes leads to increased synthesis of the precursors of glyceroneogenesis?
A. PEP carboxykinase
B. Acyl transferase
C. Acyl co-A synthase
D. Phosphatidic acid phosphatase
Answer: A
Clarification: The higher activity of PEP carboxykinase leads to increased synthesis of the precursors of glyceroneogenesis.

9. Dihydroxyacetone phosphate precursor of glycerol 3-phosphate is derived from ___________
A. Glycerol
B. Triacylglycerol
C. Glycerol 3-phosphate
D. Pyruvate
Answer: D
Clarification: Dihydroxyacetone phosphate precursor of glycerol 3-phosphate is derived from pyruvate via glyceroneogenesis.

10. Biological steroid derived from cholesterol is ___________
A. Clenbuterol
B. Cortisol
C. Winstrol
D. Dianabol
Answer: B
Clarification: Biological steroid derived from cholesterol is cortisol.

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Biochemistry Multiple Choice Questions on “Coordinated Regulation of Glycolysis and Gluconeogenesis”.

1. Gluconeogenesis responds to which of the following?
A. Hormonal control
B. pH control
C. Temperature control
D. Blood control

Answer: A
Clarification: When the blood glucose level decreases, the hormone glucagon signals the liver to produce and release more glucose and to stop consuming it for its own needs. One source of glucose is gluconeogenesis.

2. When blood sugar levels fall, glycolysis is halted in liver to allow ___________
A. Homeostasis
B. Anaerobic respiration
C. Aerobic respiration
D. Gluconeogenesis

Answer: D
Clarification: Gluconeogenesis produces glucose in order to compensate the fall.

3. How many steps are catalyzed by the same enzymes in both glycolysis and gluconeogenesis?
A. 6
B. 7
C. 8
D. 9

Answer: B
Clarification: Phosphohexose isomerase, aldolase, triose phosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, phosphoglycerate mutase and enolase are the enzymes which catalyze the reactions in both glycolysis and gluconeogenesis.

4. How many steps are catalyzed by different enzymes in glycolysis and gluconeogenesis?
A. 2
B. 3
C. 4
D. 5

Answer: B
Clarification: Hexokinase, phosphofructokinase-1 and pyruvate kinase in glycolysis, Glucose 6-phosphatase, fructose 1, 6-bisphosphatase, PEP carboxykinase and pyruvate carboxylase in gluconeogenesis.

5. Three reactions of glycolysis are so exergonic, which are not catalyzed by?
A. Hexokinase
B. PFK-1
C. Pyruvate kinase
D. Pyruvate dehydrogenase

Answer: D
Clarification: Three glycolytic enzymes are subjected to allosteric regulation: hexokinase IV, PFK-1 and pyruvate kinase.

6. What are the effects of increased concentration of citrate?
A. Increases the inhibitory effect of ATP
B. Decreases the inhibitory effect of ATP
C. Increases the activity of ATP
D. Increases the activity of AMP

Answer: A
Clarification: Citrate is a key intermediate in the aerobic oxidation of pyruvate, fatty acids and amino acids. It serves as an allosteric regulator of PFK-1; its high concentration increases the inhibitory effect of ATP, further reducing the flow of glucose through glycolysis.

7. The second control point in gluconeogenesis is the reaction catalyzed by ___________
A. Pyruvate kinase
B. Pyruvate dehydrogenase
C. FBPase-1
D. PFK-1

Answer: C
Clarification: The second control point in gluconeogenesis is the reaction catalyzed by fructose 1, 6-bisphosphatase-1.

8. Which of the following statements is true about PFK-1?
A. It is stimulated by AMP and ADP
B. It is stimulated by citrate and ATP
C. It is inhibited by AMP and ADP
D. It is stimulated by citrate and ADP

Answer: A
Clarification: AMP promotes glycogen degradation and glycolysis by activating glycogen phosphorylase and stimulating the activity of phosphofructokinase-1. ATP and citrate are allosteric inhibitors.

9. Which of the following statements is true regarding acetyl co-A?
A. It stimulates pyruvate dehydrogenase
B. It stimulates pyruvate carboxylase
C. It inhibits pyruvate carboxylase
D. It stimulates hexokinase

Answer: B
Clarification: Gluconeogenesis is regulated at the level of pyruvate carboxylase which is activated by acetyl co-A.

10. Which of the following is a potent regulator of glycolysis and gluconeogenesis?
A. Fructose 2, 6-bisphosphate
B. Fructose 1, 6-bisphosphate
C. Fructose 6-phosphate
D. Glucose 1, 6-bisphosphate

Answer: A
Clarification: The hormonal regulation of glycolysis and gluconeogenesis is mediated by fructose 2, 6-bisphosphate.

Biochemistry Multiple Choice Questions on “G Protein – Coupled Receptors and Second Messengers”.

1. Which out of the following statements is true about G-protein couple receptors?
A. The N-terminal chain is extracellular and C-terminal chain is intracellular
B. It contains 5 trans-membrane hydrophobic sections
C. There are more extracellular loops than intracellular loops
D. The binding region for G-protein involves 2 extracellular loops
Answer: A
Clarification: GPCR is characterized by an extracellular N-terminus and an intracellular C-terminus.

2. Which of the following is not a G-protein coupled receptor?
A. Glycine receptor
B. Adrenergic receptor
C. Glutamate receptor
D. Muscarinic receptor
Answer: A
Clarification: Glycine receptor is a neurotransmitter but not a GPCR.

3. Protein kinase A is ____________
A. Completely inhibited by cyclic AMP
B. Allosterically activated by cyclic AMP
C. Affected by cyclic AMP only under unusual circumstances
D. Activated by covalent binding of cyclic AMP
Answer: B
Clarification: Protein kinase A is activated when cAMP allosterically binds to a regulatory peptide.

4. Which out of the following is not involved in signal transduction by β-adrenergic receptor pathway?
A. GTP
B. ATP
C. cAMP
D. cGMP
Answer: C
Clarification: cAMP is not involved in signal transduction by β-adrenergic receptor pathway.

5. Which of the following catalyzes the cutting of PIP2 into 2 moles of IP3 and diacylglycerol in cell signaling?
A. Phosphokinase C
B. Phospholipase C
C. Lipokinase
D. Phosphodiesterase C
Answer: B
Clarification: PLC also named as phospholipase grabs onto PIP2 and cuts it into diacylglycerol and IP3.

6. The binding of ligands to many GPCRs leads to ___________
A. Decrease in concentration of certain intracellular signal molecules called second messengers
B. Increase in concentration of certain intracellular signal molecules called second messengers
C. Decrease in concentration of certain extracellular signal molecules called first messengers
D. Increase in concentration of certain extracellular signal molecules called first messengers
Answer: A
Clarification: The binding of ligands to many GPCRs leads to decrease in concentration of second messengers.

7. A hormone or ligand can be considered as ___________
A. First messenger
B. Second messenger
C. Third messenger
D. Fourth messenger
Answer: A
Clarification: Hormones are often considered to be first messengers, IP3, cAMP and cGMP are considered to be second messengers.

8. Which of the following serves as a neurotransmitter in adrenergic neurons?
A. Serotonin
B. Epinephrine
C. Dopamine
D. Histamine
Answer: B
Clarification: Adrenaline or epinephrine serves as a neurotransmitter in adrenergic neurons.

9. Which second messenger signals the release of Ca⁺² from endoplasmic reticulum?
A. IP3
B. 1, 2 diacyl glycerol
C. cAMP
D. cGMP
Answer: A
Clarification: IP3 binds to the receptor present on endoplasmic reticulum causing it to release calcium ions.

10. GPCR is comprised of ___________
A. 7 transmembrane helices
B. 8 transmembrane helices
C. 9 transmembrane helices
D. 10 transmembrane helices
Answer: A
Clarification: GPCRs are 7 transmembrane domain receptors.

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Biochemistry Multiple Choice Questions on “DNA Cloning: The Basics-1”.

1. Which of the following does not act as a restriction enzyme?
A. EcorI
B. BamHI
C. HindIII
D. polydeoxyribonucleotide synthase
Answer: D
Clarification: Polydeoxtribonucleotide synthase is a DNA ligase.

2. Which of the following enzyme is responsible for making a DNA copy from RNA?
A. Reverse transcriptase
B. DNA polymerase
C. RNA polI
D. RNA polII
Answer: A
Clarification: Reverse transcriptase generates complementary DNA from RNA template.

3. Which of the following statements is true?
A. Exonuclease III removes nucleotide residues from the 3’ ends of a DNA strand
B. Bacteriophage lambda exonuclease removes terminal phosphates
C. Alkaline phosphatase removes nucleotides from 5‘ends
D. Kinase adds homopolymer tails to the 3’ –OH ends of a linear duplex
Answer: A
Clarification: Bacteriophage lambda exonuclease removes nucleotides from 5‘ends.
Alkaline phosphatase removes terminal phosphates
Terminal transferase adds homopolymer tails to the 3’ –OH ends of a linear duplex.

4. Which of the following can be termed as a restriction modification system?
A. Restriction endonuclease + methylase
B. DNA ligase + methylase
C. Restriction endonuclease + acetylase
D. DNA ligase + acetylase
Answer: A
Clarification: (Restriction endonuclease + methylase) is termed as a restriction modification system.

5. Which of the following is true about restriction endonucleases?
A. Type I and II requires ATP to move along DNA
B. Type I, II and III requires ATP to move along DNA
C. Type II requires no ATP and cleaves DNA within recognition sequence
D. Type II requires ATP and cleaves DNA within recognition sequence
Answer: C
Clarification: Type I and III requires ATP to move along DNA.

6. Which of the following enzymes’ combined action leads to the generation of sticky ends in the plasmid vector?
A. Alkaline phosphatase and terminal transferase
B. Exonuclease III and alkaline phosphatase
C. Bacteriophage lambda exonuclease and terminal transferase
D. Exonuclease III and terminal transferase
Answer: C
Clarification: The combined action of bacteriophage lambda exonuclease and terminal transferase
lead to the generation of sticky ends in plasmid vector.

7. Generally a plasmid vector contains how many elements?
A. 1
B. 2
C. 3
D. 4
Answer: C
Clarification: Cloning site, drug resistant gene and replication origin are the 3 elements in a plasmid vector.

8. To make the recombinant plasmid permeable to DNA molecules, which of the chemicals is added?
A. MgCl₂
B. CaCl₂
C. NaCl
D. HCl
Answer: B
Clarification: The cells are treated with CaCl₂ to make them permeable to DNA molecules through a process called transformation.

9. Which of the following statements is false?
A. The cells which take up recombinant plasmids are drug resistant
B. The cells with no recombinant plasmids are drug resistant
C. Plasmid replication is independent of cell’s division
D. The cells containing recombinant plasmid are called transformed cells
Answer: A
Clarification: Recombinant plasmid contains a drug resistant gene.

10. The extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule is generally termed as __________
A. Chromosome
B. Plasmid
C. Genomic DNA
D. Bacteriophage
Answer: B
Clarification: Plasmid is an extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule.

11. E.cor1 is a __________
A. DNA ligase enzyme
B. Restriction endonuclease
C. A vector used for insulin synthesis
D. A plasmid used as a vector
Answer: B
Clarification: Ecor1 is a restriction enzyme that cleaves vector at the cloning site.

12. In which stage of genetic engineering a probe is used?
A. Cleaving DNA
B. Recombining DNA
C. Cloning
D. Screening
Answer: D
Clarification: In hybridization, which is one of the methods of screening, a probe is used.

13. What is a DNA library?
A. A DNA fragment inserted into a vector
B. A general collection of all genes sequenced thus far
C. All DNA fragments identified with a probe
D. A collection of DNA fragments that make up the entire genome of a particular organism
Answer: D
Clarification: DNA library is a collection of DNA fragments representing the entire DNA of an organism.

14. Which of the following enzyme is required for end to end joining of DNA?
A. DNA ligase
B. Restriction endonuclease
C. RNA polymerase
D. DNA polymerase
Answer: A
Clarification: DNA ligase ligates both blunt and sticky ends of DNA.

15. Repressor molecules bind to __________
A. Operator
B. Promoter
C. Enhancer
D. Hormone response element
Answer: A
Clarification: An operator lies partially within the promoter, repressor binds to the DNA at operator region inhibiting the expression of genes.

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