Proteins – chemistry, sources, preparation, evaluation, preservation, storage, therapeutic uses and commercial utility MCQs With Answer

Proteins – chemistry, sources, preparation, evaluation, preservation, storage, therapeutic uses and commercial utility

Proteins are polymers of amino acids linked by peptide bonds and exhibit primary, secondary, tertiary and quaternary structures essential for biological function. B. Pharm students must understand protein chemistry, natural and recombinant sources, extraction and purification techniques (chromatography, ultrafiltration, dialysis), analytical evaluation (SDS-PAGE, HPLC, UV absorbance, amino acid analysis), and stability issues including denaturation, aggregation and isoelectric point effects. Preservation and storage strategies (lyophilization, cold chain, stabilizers) impact therapeutic proteins such as insulin, monoclonal antibodies and enzymes used commercially in pharmaceuticals, diagnostics and industry. Knowledge of formulation, potency assays and regulatory considerations is critical. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which bond links amino acids in a protein polypeptide chain?

• Glycosidic bond
• Peptide bond
• Phosphodiester bond
• Disulfide bond

Correct Answer: Peptide bond

Q2. The primary structure of a protein refers to:

• The overall 3D folding of the polypeptide
• The sequence of amino acids
• The pattern of alpha helices and beta sheets
• The assembly of multiple subunits

Correct Answer: The sequence of amino acids

Q3. Which amino acid is unique for forming disulfide bonds commonly stabilizing tertiary structure?

• Methionine
• Cysteine
• Lysine
• Proline

Correct Answer: Cysteine

Q4. Salting out is a method used for:

• Determining protein sequence
• Purifying proteins by precipitation using high salt
• Measuring protein concentration by color change
• Removing nucleic acids from protein samples

Correct Answer: Purifying proteins by precipitation using high salt

Q5. Which technique separates proteins primarily by molecular weight under denaturing conditions?

• Ion-exchange chromatography
• SDS-PAGE
• Isoelectric focusing
• Size-exclusion chromatography in native buffer

Correct Answer: SDS-PAGE

Q6. Which assay is based on dye binding to protein and is rapid for concentration measurement?

• Bradford assay
• BCA assay
• Lowry assay
• Kjeldahl method

Correct Answer: Bradford assay

Q7. Isoelectric point (pI) of a protein is the pH at which the protein:

• Has maximum solubility
• Has no net electric charge
• Is fully denatured
• Forms covalent aggregates

Correct Answer: Has no net electric charge

Q8. Lyophilization (freeze-drying) is primarily used to:

• Increase proteolytic degradation
• Improve long-term stability and storage of proteins
• Remove disulfide bonds
• Denature native tertiary structure

Correct Answer: Improve long-term stability and storage of proteins

Q9. A common excipient used as a lyoprotectant to stabilize proteins during freeze-drying is:

• Sodium chloride
• Sucrose
• Hydrochloric acid
• Polyethylene glycol 4000

Correct Answer: Sucrose

Q10. Which preservation method is most likely to minimize ice crystal damage and aggregation for sensitive proteins?

• Room temperature storage
• Repeated freeze–thaw cycles
• Deep freezing with controlled-rate freezing
• Heating at 60°C

Correct Answer: Deep freezing with controlled-rate freezing

Q11. Enzymes used therapeutically (e.g., streptokinase) are classified as which type of proteins?

• Structural proteins
• Carrier proteins
• Catalytic proteins
• Storage proteins

Correct Answer: Catalytic proteins

Q12. Which chromatographic method separates proteins based on charge?

• Affinity chromatography
• Size-exclusion chromatography
• Ion-exchange chromatography
• Hydrophobic interaction chromatography

Correct Answer: Ion-exchange chromatography

Q13. Monoclonal antibodies used as therapeutics are often analyzed for purity by:

• Infrared spectroscopy only
• SDS-PAGE and size-exclusion HPLC
• Paper chromatography
• Acid titration

Correct Answer: SDS-PAGE and size-exclusion HPLC

Q14. Glycosylation influences therapeutic protein properties by affecting:

• Only the primary sequence
• Solubility, immunogenicity, and half-life
• Only UV absorbance at 280 nm
• Resistance to all proteases

Correct Answer: Solubility, immunogenicity, and half-life

Q15. Endotoxin removal is critical for recombinant protein therapeutics produced in Gram-negative bacteria because endotoxins can:

• Enhance protein folding
• Cause fever and immune reactions in patients
• Increase protein solubility
• Promote glycosylation

Correct Answer: Cause fever and immune reactions in patients

Q16. A common method to quantify protein concentration based on peptide bonds absorbing UV light uses measurement at which wavelength?

• 220 nm
• 280 nm
• 340 nm
• 600 nm

Correct Answer: 280 nm

Q17. Which stress factor is most directly responsible for irreversible protein denaturation during manufacturing?

• Isotonic buffer conditions
• Extreme pH and elevated temperature
• Presence of stabilizers like trehalose
• Mild agitation at 4°C

Correct Answer: Extreme pH and elevated temperature

Q18. Affinity chromatography exploits:

• Size differences alone
• Specific binding interactions between protein and ligand
• Electric charge repulsion
• Volatility of proteins

Correct Answer: Specific binding interactions between protein and ligand

Q19. Protein aggregation during storage often reduces therapeutic potency by:

• Increasing monomer concentration
• Altering bioavailability and eliciting immune responses
• Enhancing target binding specificity
• Reducing molecular weight

Correct Answer: Altering bioavailability and eliciting immune responses

Q20. Which analytical technique provides information on molecular mass and heterogeneity of a protein with high accuracy?

• Mass spectrometry
• Paper electrophoresis
• UV-visible colorimetric test
• Light microscopy

Correct Answer: Mass spectrometry

Q21. Recombinant proteins are commonly expressed in which system to obtain human-like glycosylation patterns?

• E. coli bacterial expression
• Saccharomyces cerevisiae only
• Mammalian cell culture (e.g., CHO cells)
• Plant chloroplast transformation only

Correct Answer: Mammalian cell culture (e.g., CHO cells)

Q22. The Lowry and BCA assays are both used to:

• Determine protein tertiary structure
• Measure protein concentration colorimetrically
• Separate proteins by charge
• Lyophilize protein formulations

Correct Answer: Measure protein concentration colorimetrically

Q23. Which preservative or stabilizer protects proteins from aggregation by preferential hydration?

• Sodium dodecyl sulfate (SDS)
• Nonionic surfactants like polysorbate 80
• Strong acids
• Organic solvents such as ethanol

Correct Answer: Nonionic surfactants like polysorbate 80

Q24. ELISA is primarily used to:

• Quantify DNA sequence
• Detect and quantify specific proteins or antibodies
• Measure osmolarity of a solution
• Determine lipid composition

Correct Answer: Detect and quantify specific proteins or antibodies

Q25. Which storage condition is generally recommended for long-term preservation of most protein therapeutics?

• Ambient temperature in light
• Lyophilized at low moisture with refrigeration or freezing
• Repeated cycles of warming to 37°C
• Stored in strong reducing agents

Correct Answer: Lyophilized at low moisture with refrigeration or freezing

Q26. Pepsin and trypsin are examples of:

• Structural proteins used in formulations
• Proteases that hydrolyze peptide bonds
• Carbohydrate-modifying enzymes
• Non-biological excipients

Correct Answer: Proteases that hydrolyze peptide bonds

Q27. Which parameter is critical when designing protein formulations to reduce charge-mediated aggregation?

• Sterility testing only
• Adjusting pH away from the protein’s isoelectric point
• Adding strong oxidizers
• Increasing ionic strength to infinity

Correct Answer: Adjusting pH away from the protein’s isoelectric point

Q28. Commercial enzyme preparations used in industry (e.g., proteases for detergents) must be evaluated for:

• Only color
• Activity, stability under use conditions, and cost-effectiveness
• Ability to form crystals for X-ray only
• Reactivity with heavy metals exclusively

Correct Answer: Activity, stability under use conditions, and cost-effectiveness

Q29. Which factor increases immunogenic risk of a therapeutic protein?

• Human sequence and proper glycosylation
• High levels of aggregates and impurities
• Single, monodisperse formulation
• Controlled cold-chain storage

Correct Answer: High levels of aggregates and impurities

Q30. Sterile filtration of protein therapeutics is commonly performed using which pore size membrane to remove bacteria while retaining protein?

• 0.22 µm
• 5 µm
• 50 nm
• 10 µm

Correct Answer: 0.22 µm

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com