Category: Biochemistry Objective Questions

Biochemistry Multiple Choice Questions on “Protein Tertiary and Quaternary Structures”.

1. Fibroin is rich in ________
A. Alanine and Glycine
B. Alanine
C. Glycine
D. Pro
Answer: A
Clarification: Fibroin is rich in Alanine and Glycine residues, permitting a close packing of β sheets and an interlocking arrangement of R groups.

2. Which of the following bonds are not involved in tertiary type of protein structure?
A. Disulfide bond
B. Hydrogen bonding
C. Salt bridges
D. Hydrophilic interactions
Answer: D
Clarification: Hydrophobic interactions are present in tertiary type of protein structure.

3. Which of the following does not possess a quaternary structure?
A. Myoglobin
B. Lactate dehydrogenase
C. Immunoglobin M
D. Creatine Phospho Kinase
Answer: A
Clarification: Myoglobin is a monomer, so it does not possess a quaternary structure.

4. Which of the following is abundantly found in collagen?
A. Glycine
B. Serine
C. Alanine
D. Tryptophan
Answer: A
Clarification: Each three amino acids of the collagen peptide chain is a glycine. It is thus an abundant amino acid that is important for collagen structure.

5. Which of the following is first determined as oligomer?
A. Myoglobin
B. Collagen
C. Keratin
D. Hemoglobin
Answer: D
Clarification: Hemoglobin contains four polypeptide chains and four heme prosthetic groups in which iron atoms are present in Fe⁺² state.

6. Which of the following is false?
A. Lysozyme has S-S linkage
B. Ribonuclease has S-S linkage
C. Heme group in cytochrome c is covalently linked to the protein on two sides
D. Ribonuclease has SH-SH linkage
Answer: D
Clarification: Lysozyme and ribonuclease have disulfide linkages.

7. Which of the following enzyme is secreted by the pancreas?
A. Ribonuclease
B. Lysozyme
C. Cytochrome c
D. Myoglobin
Answer: A
Clarification: Ribonuclease is secreted by the pancreas into small intestine, where it catalyses the hydrolysis of certain bonds in ribonucleic acids present in the ingested food.

8. Which of the following is a component of mitochondria?
A. Ribonuclease
B. Lysozyme
C. Cytochrome c
D. Myoglobin
Answer: C
Clarification: Cytochrome c which is a heme protein is a component of the respiratory chain of mitochondria.

9. Which of the following serves as bactericidal agent?
A. Ribonuclease
B. Lysozyme
C. Cytochrome c
D. Myoglobin
Answer: B
Clarification: Lysozyme can lyse, or degrade bacterial cell walls, so it serves as a bactericidal agent.

10. Which of the following is false about fibrous protein?
A. It is in rod or wire like shape
B. Keratin and collagen are the best examples
C. Hemoglobin is the best example
D. It provides structural support for cells and tissues
Answer: C
Clarification: Hemoglobin is the best example of globular protein.

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Biochemistry Multiple Choice Questions on “Biosynthesis of Membrane Phospholipids”.

1. Displacement of CMP through nucleophilic attack by the hydroxyl group of serine yields ___________
A. Phosphatidyl serine
B. Phosphatidyl glycerol 3-phosphate
C. Phosphatidyl glycerol
D. Phosphatidylethanolamine
Answer: A
Clarification: Displacement of CMP through nucleophilic attack by the hydroxyl group of serine yields phosphatidyl serine.

2. Displacement of CMP through a nucleophilic attack by the hydroxyl group of C-1 hydroxyl of glycerol 3-phosphate yields ___________
A. Phosphatidyl serine
B. Phosphatidyl glycerol 3-phosphate
C. Phosphatidyl glycerol
D. Phosphatidylethanolamine
Answer: B
Clarification: Displacement of CMP through nucleophilic attack by the hydroxyl group of C-1 hydroxyl of glycerol 3-phosphate yields phosphatidyl glycerol 3-phosphate.

3. Which of the following is a molecular formula of cholesterol?
A. C₂₇H₄₅OH
B. C₂₈H₄₅OH
C. C₂₉H₄₅OH
D. C₂₃H₄₅OH
Answer: A
Clarification: C₂₇H₄₅OH is the molecular formula of cholesterol.

4. Which of the following is involved in the bio-signaling pathway that includes membrane turnover and exocytosis?
A. Phosphatidylinositol
B. Phosphatidyl glycerol
C. Myoinositol
D. Phosphatidyl glycerol and myoinositol
Answer: A
Clarification: Phosphatidylinositol is involved in the bio-signaling pathway that includes membrane turnover and exocytosis.

5. The precursor of eicosanoids in human is ___________
A. Ceramide
B. Arachidonic acid
C. Cholesterol
D. Squaline
Answer: B
Clarification: The precursor of eicosanoids in human is arachidonic acid.

6. Which of the following is the simplest hydrophilic moiety present in membrane lipids?
A. Glucose
B. Amino group
C. Hydroxyl group
D. Phosphate group
Answer: C
Clarification: Hydroxyl group is the simplest hydrophilic moiety present in membrane lipids.

7. Which of the following is considered as the structural parent of all sphingolipids?
A. Sphingosine
B. Ceramide
C. Lecithin
D. Sphingomyelin
Answer: B
Clarification: N-acyl fatty acid derivative of sphingosine at C2 is called ceramide, which forms the backbone of sphingolipids.

8. The most complex sphingolipid is ___________
A. Cerebroside
B. Gangleoside
C. Globoside
D. Ceramide
Answer: B
Clarification: Gangleosides have the most complex structure.

9. Phosphatidylserine is derived only from ___________
A. Phosphatidylethanolamine
B. Phosphatidyl glycerol
C. Phosphatidyl choline
D. CDP-diacylglycerol
Answer: A
Clarification: Decarboxylation of phosphatidylserine produces phosphatidylethanolamine.

10. Cerebroside is also called as ___________
A. Sphingomyelin
B. N-acylsphingosine
C. Sphinganine
D. Gangliosides
Answer: A
Clarification: Cerebroside is also called as sphingomyelin.

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Biochemistry Questions on “Coordinated Regulation of Glycogen Synthesis and Breakdown”.

1. Glucagon and epinephrine stimulate glycogen breakdown to glucose 6-phosphate ________
A. Directly by binding to glycogen phosphorylase
B. Indirectly by first stimulating adenylate cyclase to make cAMP
C. Only in the liver
D. Only in muscle cells

Answer: B
Clarification: The second messenger cAMP increases in concentration in response to stimulation by epinephrine in muscle or glucagon in liver.

2. Which compounds are responsible for the coordinated regulation of glucose and glycogen metabolism?
A. NADH
B. NAD⁺
C. Acetyl co-A
D. Fructose 2, 6-bisphosphate

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

3. Glycogen synthase a is activated by ___________
A. Phosphorylation catalyzed by GSK3
B. Dephosphorylation catalyzed by GSK3
C. Phosphorylation catalyzed by pyruvate kinase
D. Phosphorylation catalyzed by pyruvate carboxylase

Answer: A
Clarification: A protein kinase (PDK-1) that is activated when bound to PIP3 activates a second protein kinase (PKB. which phosphorylates glycogen synthase kinase 3 (GSK-3). The inactivation of GSK3 allows PP1 to dephosphorylate glycogen synthase converting it to its active form.

4. Glucagon is released from ___________
A. Muscle
B. Pancreas
C. Kidneys
D. Epithelial tissues

Answer: B
Clarification: Glucagon is released from pancreas and causes the liver to convert glycogen to glucose.

5. Glucose 6-phosphatase is present only in ___________
A. Liver
B. Muscle
C. Epithelial tissues
D. Kidneys

Answer: A
Clarification: Glucose 6-phosphatase which hydrolyzes glucose 6-phosphate is present only in liver. Other tissues lack glucose 6-phosphatase.

6. Which of the following enzymes is involved in the positive regulation of glycolysis/gluconeogenesis?
A. Hexokinase II
B. Hexokinase IV
C. PFK-2/FBPase-2
D. Pyruvate kinase

Answer: C
Clarification: Increased expression of PFK-2/FBPase-2 regulates glycolysis/gluconeogenesis.

7. Which of the following enzymes is involved in fatty acid synthesis?
A. Hexokinase II
B. Hexokinase IV
C. PFK-2/FBPase-2
D. Pyruvate dehydrogenase

Answer: D
Clarification: Hexokinase II and hexokinase IV involved in glycolysis.

8. Which of the following is involved in triacylglycerol synthesis?
A. Hexokinase II
B. Acyl co-A glycerol transferases
C. PFK-2/FBPase-2
D. Pyruvate dehydrogenase

Answer: B
Clarification: Hexokinase II involved in glycolysis, pyruvate dehydrogenase involved in fatty acid synthesis.

9. Which of the following is involved in pentose phosphate pathway?
A. Glucose 6-phosphate dehydrogenase
B. Acyl co-A glycerol transferases
C. PFK-2/FBPase-2
D. Pyruvate dehydrogenase

Answer: A
Clarification: Acyl co-A glycerol transferases involved in triacylglycerol synthesis, pyruvate dehydrogenase involved in fatty acid synthesis.

10. Which of the following enzyme’s gene expression is slowed by insulin?
A. Hexokinase II
B. Hexokinase IV
C. PEP carboxykinase
D. Pyruvate kinase

Answer: C
Clarification: Insulin stimulates the transcription of the genes that encode hexokinase II, hexokinase IV and pyruvate kinase.

Biochemistry Multiple Choice Questions on “Multivalent Scaffold Proteins and Membrane Rafts”.

1. The specificity of signaling pathways does not include ___________
A. Migration of signal proteins into membrane rafts
B. Assembly of large multiprotein complexes
C. Phosphorylation of target proteins at Ser, Thr/Tyr residues
D. Flippase-catalyzed movement of phospholipids from the inner to the outer leaflet
Answer: D
Clarification: The specificity of signaling pathways does not include flippase-catalyzed movement of phospholipids from the inner to the outer leaflet.

2. Which of the following directly phosphorylate tyrosines to start a kinase protein enzymatic cascade?
A. Receptor tyrosine kinase
B. Receptor guanylyl cyclases
C. Receptor serine kinase
D. Receptor threonine kinase
Answer: A
Clarification: Only receptor tyrosine kinase directly phosphorylates tyrosine to start a kinase protein enzymatic cascade.

3. PTB domains bind to ___________
A. Phosphorylated tyrosine
B. Phosphoryated threonine
C. Phosphorylated serine
D. Phosphorylated cysteine
Answer: A
Clarification: Phosphotyrosine binding domain binds to phosphotyrosine.

4. Scaffold protein in insulin signal transduction ___________
A. KSR
B. IRS-1
C. MEKK1
D. AKAP
Answer: B
Clarification: IRS-1 is an adapter protein in insulin that codes for IRS1 gene.

5. Which of the following is involved in extrinsic cell death pathway?
A. Heterotrimeric G protein complex
B. TRADD
C. IRS-1
D. Protein-kinase A
Answer: B
Clarification: TRADD, tumor necrosis factor receptor type 1-associated death domain protein is involved in extrinsic cell death pathway.

6. Which of the following converts GTP to cGMP to start its enzymatic cascade?
A. Receptor guanylyl cyclase
B. Receptor adenylyl cyclase
C. Calmodulin
D. Protein kinase-A
Answer: A
Clarification: Receptor adenylyl cyclase converts ATP to cAMP.

7. Which of the following are stimulated to become membrane associated upon binding of insulin to the insulin receptor?
A. PH-domain
B. PTB
C. SH3
D. SH2
Answer: A
Clarification: PH domain is stimulated to become membrane associated upon binding of insulin to the insulin receptor.

8. Which of the following is involved in phospho-tyrosine binding?
A. SH2
B. SH3
C. PTB
D. PH
Answer: A
Clarification: SH3 is involved in proline rich motif binding.

9. Which of the following is involved in proline rich motif binding?
A. SH2
B. SH3
C. PTB
D. PH
Answer: B
Clarification: SH2 is involved in phospho-tyrosine binding.

10. Which of the following is not a downstream component?
A. Ras
B. MEK
C. ERK
D. PIP3
Answer: D
Clarification: Ras, MEK and ERK are the downstream components.

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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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