Biological role of proteins MCQs With Answer

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Understanding the biological role of proteins is essential for B. Pharm students preparing for pharmacology, biochemistry, and therapeutics. This concise guide introduces protein functions—enzymes, structural proteins, transporters, signaling molecules, immunoglobulins, and peptide hormones—highlighting relevance to drug action, metabolism, and disease. Focused on mechanisms such as enzyme catalysis, receptor binding, membrane transport, and post-translational modifications, these MCQs with answers reinforce core concepts, clinical correlations, and exam-ready facts. Keywords include Biological role of proteins MCQs With Answer, B.Pharm, protein functions, enzymes in drug metabolism, and protein structure-function relationships, and practical applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which bond links amino acids together to form the primary structure of proteins?

  • Hydrogen bond
  • Peptide bond
  • Disulfide bond
  • Ionic bond

Correct Answer: Peptide bond

Q2. Which level of protein structure is primarily stabilized by hydrogen bonding between backbone NH and CO groups?

  • Primary structure
  • Secondary structure
  • Tertiary structure
  • Quaternary structure

Correct Answer: Secondary structure

Q3. Which amino acid is unique for introducing kinks in alpha helices due to its cyclic structure?

  • Glycine
  • Proline
  • Alanine
  • Serine

Correct Answer: Proline

Q4. Which protein is the major carrier of fatty acids and many drugs in plasma, influencing drug distribution?

  • Hemoglobin
  • Albumin
  • Fibrinogen
  • Transferrin

Correct Answer: Albumin

Q5. Enzymes accelerate reactions primarily by

  • Increasing activation energy
  • Decreasing activation energy
  • Changing the equilibrium constant
  • Altering substrate concentration

Correct Answer: Decreasing activation energy

Q6. The Michaelis constant (Km) represents

  • The maximum reaction rate
  • The substrate concentration at half Vmax
  • The affinity between enzyme and inhibitor
  • The turnover number

Correct Answer: The substrate concentration at half Vmax

Q7. A competitive inhibitor affects enzyme kinetics by

  • Decreasing Vmax and increasing Km
  • Increasing Vmax and decreasing Km
  • Increasing Km without changing Vmax
  • Decreasing Km without changing Vmax

Correct Answer: Increasing Km without changing Vmax

Q8. Allosteric enzymes often display which type of kinetic behavior?

  • Linear kinetics
  • Michaelis-Menten hyperbolic curve
  • Sigmoidal (cooperative) kinetics
  • First-order kinetics only

Correct Answer: Sigmoidal (cooperative) kinetics

Q9. Which protein is responsible for oxygen transport in red blood cells and shows cooperative binding?

  • Myoglobin
  • Albumin
  • Hemoglobin
  • Collagen

Correct Answer: Hemoglobin

Q10. Myoglobin differs from hemoglobin mainly because it

  • Is a tetramer and shows cooperativity
  • Binds CO2 preferentially
  • Is a monomer and stores oxygen in muscle
  • Is a membrane receptor

Correct Answer: Is a monomer and stores oxygen in muscle

Q11. Which post-translational modification commonly regulates enzyme activity and signal transduction?

  • Glycolysis
  • Phosphorylation
  • Proteasomal degradation
  • Transcription

Correct Answer: Phosphorylation

Q12. Protein glycosylation is important for

  • DNA replication fidelity
  • Membrane receptor recognition and stability
  • RNA splicing
  • ATP synthesis in mitochondria

Correct Answer: Membrane receptor recognition and stability

Q13. Which class of proteins includes antibodies essential for adaptive immunity?

  • Enzymes
  • Immunoglobulins
  • Transporters
  • Structural proteins

Correct Answer: Immunoglobulins

Q14. Zymogens are

  • Inactive enzyme precursors activated by proteolysis
  • Allosteric activators of enzymes
  • Membrane-bound receptors
  • Chaperone proteins

Correct Answer: Inactive enzyme precursors activated by proteolysis

Q15. Which degradation pathway labels proteins with ubiquitin for proteasomal destruction?

  • Lysosomal autophagy
  • Ubiquitin-proteasome system
  • Glycolytic pathway
  • ER secretory pathway

Correct Answer: Ubiquitin-proteasome system

Q16. Heat shock proteins (molecular chaperones) primarily function to

  • Degrade misfolded proteins
  • Assist proper protein folding and prevent aggregation
  • Synthesize proteins on ribosomes
  • Transport proteins across membranes

Correct Answer: Assist proper protein folding and prevent aggregation

Q17. Which amino acid contains a thiol group that forms disulfide bonds important for tertiary structure?

  • Methionine
  • Cysteine
  • Tyrosine
  • Serine

Correct Answer: Cysteine

Q18. Prion diseases result from proteins that

  • Are overphosphorylated
  • Adopt an infectious misfolded conformation that induces aggregation
  • Have increased enzymatic activity
  • Are secreted at excessive levels

Correct Answer: Adopt an infectious misfolded conformation that induces aggregation

Q19. Which plasma protein is essential for blood clot formation by being converted to fibrin?

  • Albumin
  • Fibrinogen
  • Transferrin
  • Globin

Correct Answer: Fibrinogen

Q20. Cytochrome P450 enzymes are important in drug metabolism because they

  • Conjugate drugs directly to glucuronic acid
  • Oxidize xenobiotics, increasing polarity for excretion
  • Transport drugs across the BBB
  • Act as membrane ion channels

Correct Answer: Oxidize xenobiotics, increasing polarity for excretion

Q21. Which structural protein provides tensile strength to connective tissues and is abundant in bone and skin?

  • Actin
  • Keratin
  • Collagen
  • Tubulin

Correct Answer: Collagen

Q22. The quaternary structure of a protein refers to

  • The amino acid sequence
  • Local folding patterns like alpha helices
  • Three-dimensional folding of a single polypeptide
  • The assembly of multiple polypeptide subunits

Correct Answer: The assembly of multiple polypeptide subunits

Q23. Which protein domain is typically responsible for binding small ligands like cofactors or drugs?

  • Signal peptide
  • Active site or binding pocket
  • Transmembrane helix
  • Coiled-coil domain

Correct Answer: Active site or binding pocket

Q24. Which cellular compartment is the primary site for secretory and membrane protein folding and glycosylation?

  • Nucleus
  • Endoplasmic reticulum
  • Mitochondria
  • Cytosol

Correct Answer: Endoplasmic reticulum

Q25. Which receptor type has intrinsic tyrosine kinase activity and mediates many growth factor signals?

  • G protein-coupled receptor (GPCR)
  • Ion channel receptor
  • Toll-like receptor
  • Receptor tyrosine kinase (RTK)

Correct Answer: Receptor tyrosine kinase (RTK)

Q26. Insulin is classified as which type of biomolecule?

  • Steroid hormone
  • Peptide hormone (protein)
  • Neurotransmitter
  • Fatty acid derivative

Correct Answer: Peptide hormone (protein)

Q27. Which component determines the specificity of antibody binding to antigen?

  • Fc region
  • Hinge region
  • Variable region (Fab)
  • Constant region

Correct Answer: Variable region (Fab)

Q28. Which laboratory technique separates proteins primarily by molecular weight under denaturing conditions?

  • Isoelectric focusing
  • SDS-PAGE
  • Native PAGE
  • Affinity chromatography

Correct Answer: SDS-PAGE

Q29. Enzyme turnover number (kcat) represents

  • The substrate concentration at half Vmax
  • The number of substrate molecules converted per enzyme per unit time
  • The binding affinity of enzyme for substrate
  • The inhibitor potency

Correct Answer: The number of substrate molecules converted per enzyme per unit time

Q30. Hemoglobin affinity for oxygen decreases under conditions of

  • Low CO2, high pH
  • High pH and low temperature
  • High CO2, low pH, and high 2,3-BPG
  • Presence of methemoglobin only

Correct Answer: High CO2, low pH, and high 2,3-BPG

Q31. Which modification targets proteins for lysosomal degradation via mannose-6-phosphate tagging?

  • Ubiquitination
  • N-linked glycosylation with Mannose-6-phosphate
  • Phosphorylation
  • Acetylation

Correct Answer: N-linked glycosylation with Mannose-6-phosphate

Q32. Which protein family forms the cytoskeletal tracks used by motor proteins like kinesin and dynein?

  • Actin filaments
  • Intermediate filaments
  • Microtubules (tubulin)
  • Collagen fibrils

Correct Answer: Microtubules (tubulin)

Q33. Which technique would you use to quantify a specific protein in patient serum using antigen-antibody specificity?

  • Western blot
  • ELISA
  • Mass spectrometry
  • Spectrophotometry

Correct Answer: ELISA

Q34. The term “isoenzyme” refers to

  • Different enzymes performing different reactions
  • Different molecular forms of the same enzyme catalyzing the same reaction
  • Inactive enzyme precursors
  • Enzymes bound to membranes only

Correct Answer: Different molecular forms of the same enzyme catalyzing the same reaction

Q35. Which protein modification commonly increases protein half-life by blocking degradation signals?

  • Polyubiquitination
  • N-terminal acetylation
  • Proteolytic cleavage
  • Dephosphorylation

Correct Answer: N-terminal acetylation

Q36. Which protein acts as a molecular oxygen sensor in some regulatory pathways by binding heme and modulating activity?

  • Hemoglobin only
  • HIF (hypoxia-inducible factor) regulated proteins
  • Cytochrome P450 family member exclusively
  • Albumin

Correct Answer: HIF (hypoxia-inducible factor) regulated proteins

Q37. Which drug class often inhibits proteases and is used in antiviral therapy?

  • Beta-lactam antibiotics
  • Protease inhibitors
  • Calcium channel blockers
  • Statins

Correct Answer: Protease inhibitors

Q38. Which term describes the non-protein component required for enzyme activity?

  • Apoenzyme
  • Coenzyme or prosthetic group
  • Substrate
  • Inhibitor

Correct Answer: Coenzyme or prosthetic group

Q39. Which membrane protein type spans the lipid bilayer and often forms channels or receptors?

  • Peripheral proteins
  • Lipoproteins
  • Integral (transmembrane) proteins
  • Glycolytic enzymes

Correct Answer: Integral (transmembrane) proteins

Q40. Protein misfolding leading to amyloid fibrils is characteristic of which condition?

  • Type I hypersensitivity
  • Amyloidosis and neurodegenerative diseases like Alzheimer’s
  • Acute bacterial infection only
  • Vitamin deficiency syndromes

Correct Answer: Amyloidosis and neurodegenerative diseases like Alzheimer’s

Q41. Coagulation factors are mostly which type of biomolecule?

  • Carbohydrates
  • Lipids
  • Proteins (serine proteases or glycoproteins)
  • Steroid hormones

Correct Answer: Proteins (serine proteases or glycoproteins)

Q42. Which amino acid is commonly phosphorylated to regulate protein activity in signaling pathways?

  • Phenylalanine
  • Tyrosine, serine, or threonine
  • Leucine
  • Proline only

Correct Answer: Tyrosine, serine, or threonine

Q43. Which proteomic technique separates proteins based on isoelectric point and molecular weight?

  • Two-dimensional gel electrophoresis (2D-PAGE)
  • SDS-PAGE only
  • ELISA
  • PCR

Correct Answer: Two-dimensional gel electrophoresis (2D-PAGE)

Q44. Which protein is central to innate immunity by recognizing pathogen-associated molecular patterns?

  • Immunoglobulin G (IgG)
  • Toll-like receptors (TLRs)
  • Albumin
  • Insulin

Correct Answer: Toll-like receptors (TLRs)

Q45. Which property of amino acids determines whether a protein is soluble in water?

  • Primary sequence length only
  • Proportion and distribution of hydrophobic vs hydrophilic residues
  • Number of disulfide bonds only
  • Presence of metal ions only

Correct Answer: Proportion and distribution of hydrophobic vs hydrophilic residues

Q46. Signal peptides at the N-terminus of proteins direct them to the

  • Mitochondrial matrix only
  • Secretory pathway (ER) for secretion or membrane insertion
  • Nucleus exclusively
  • Peroxisomes only

Correct Answer: Secretory pathway (ER) for secretion or membrane insertion

Q47. Which laboratory assay measures enzyme activity by monitoring product formation over time?

  • Western blot
  • Enzyme activity assay (kinetic assay)
  • Immunoprecipitation
  • Southern blot

Correct Answer: Enzyme activity assay (kinetic assay)

Q48. Which pharmacological strategy uses monoclonal antibodies to target specific proteins involved in disease?

  • Small-molecule inhibitors only
  • Monoclonal antibody therapy
  • Gene editing exclusively
  • Vaccine adjuvants only

Correct Answer: Monoclonal antibody therapy

Q49. The Hill coefficient greater than 1 for a protein indicates

  • Negative cooperativity
  • No cooperativity
  • Positive cooperativity among binding sites
  • Complete inhibition of binding

Correct Answer: Positive cooperativity among binding sites

Q50. In the context of drug development, why is understanding protein structure-function relationships vital?

  • It is only academically interesting with no practical use
  • It informs rational drug design, target validation, and predicting off-target effects
  • It replaces the need for clinical trials
  • It is only relevant for nutritional studies

Correct Answer: It informs rational drug design, target validation, and predicting off-target effects

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