Introduction to immobilization MCQs With Answer

Introduction: Introduction to immobilization MCQs With Answer

This collection of multiple-choice questions is designed for M.Pharm students studying Bioprocess Engineering and Technology. It covers fundamental and advanced aspects of immobilization of enzymes and cells, including methods (adsorption, covalent binding, entrapment, encapsulation, cross-linking), support materials, activation chemistries, reactor configurations, kinetics and mass-transfer considerations, operational stability, and practical troubleshooting. Each question targets conceptual clarity and exam relevance, helping students strengthen problem-solving skills and recall key principles. Answers are provided to facilitate self-assessment. Use these MCQs to revise technical concepts, prepare for viva/entrance exams, and deepen your understanding of immobilized biocatalyst systems.

Q1. What is the most accurate definition of immobilization in bioprocess engineering?

• Physically attaching living cells to a solid surface for microscopy
• Restriction of mobility of a biocatalyst (enzyme or cell) in a defined region of space while retaining catalytic activity
• Chemically modifying a substrate to increase solubility
• Encapsulating drugs for controlled release

Correct Answer: Restriction of mobility of a biocatalyst (enzyme or cell) in a defined region of space while retaining catalytic activity

Q2. Which set best represents the primary methods of enzyme immobilization?

• Precipitation, crystallization, lyophilization
• Adsorption, covalent binding, entrapment, encapsulation, cross-linking
• Freeze-drying, spray-drying, milling
• Sonication, homogenization, centrifugation

Correct Answer: Adsorption, covalent binding, entrapment, encapsulation, cross-linking

Q3. Which of the following is a principal advantage of immobilizing enzymes for industrial biocatalysis?

• Requirement of expensive cofactors for each cycle
• Increased product inhibition compared with free enzymes
• Ease of separation and repeated reuse leading to lower operational cost
• Complete elimination of mass transfer limitations

Correct Answer: Ease of separation and repeated reuse leading to lower operational cost

Q4. Which carrier material is most commonly used as a gentle entrapment matrix for enzymes and cells?

• Polyacrylamide activated with glutaraldehyde
• Silica gel
• Sodium alginate
• Eupergit C

Correct Answer: Sodium alginate

Q5. Which reagent is widely used as a bifunctional cross-linking agent to form covalent bonds between enzymes and supports?

• EDTA
• Glutaraldehyde
• SDS
• PBS buffer

Correct Answer: Glutaraldehyde

Q6. Which activation chemistry is commonly used to activate agarose supports for covalent enzyme immobilization?

• Carbodiimide (EDC) activation of hydroxyl groups
• Cyanogen bromide (CNBr) activation
• Alkylation with iodoacetamide
• Acetylation with acetic anhydride

Correct Answer: Cyanogen bromide (CNBr) activation

Q7. How does covalent immobilization typically affect apparent Km and Vmax of an enzyme compared with its free form?

• Apparent Km decreases and Vmax increases due to rigidification
• Apparent Km may increase and Vmax often decreases because of diffusion and steric effects
• No change in Km or Vmax ever occurs
• Both Km and Vmax always increase

Correct Answer: Apparent Km may increase and Vmax often decreases because of diffusion and steric effects

Q8. What is the defining characteristic of an entrapment immobilization method?

• Enzyme is covalently bonded to support surface via spacer arms
• Enzyme is physically confined within a porous polymeric matrix that allows substrate and product to diffuse
• Enzyme is adsorbed through weak ionic interactions on hydrophobic beads
• Enzyme is chemically cross-linked to itself without any carrier

Correct Answer: Enzyme is physically confined within a porous polymeric matrix that allows substrate and product to diffuse

Q9. Which reactor configuration is most suitable for continuous processing with immobilized enzymes in packed carriers?

• Batch stirred-tank reactor
• Packed-bed (fixed-bed) reactor
• Pulsed-gradient chromatograph
• Membrane dialysis reactor

Correct Answer: Packed-bed (fixed-bed) reactor

Q10. What is the primary limitation often encountered in immobilized enzyme systems that reduces observed reaction rates?

• Excessive solubility of the enzyme
• Mass transfer limitations (external and internal diffusion)
• Unlimited substrate availability
• Complete prevention of product inhibition

Correct Answer: Mass transfer limitations (external and internal diffusion)

Q11. The Thiele modulus is a dimensionless number used in immobilized enzyme systems. What does it express?

• Ratio of enzyme molecular weight to support pore size
• Ratio of reaction rate to internal diffusion rate within a porous particle
• Percentage of immobilized enzyme that is covalently bound
• The electrical charge density on the support surface

Correct Answer: Ratio of reaction rate to internal diffusion rate within a porous particle

Q12. Which immobilization technique is most prone to enzyme leaching under changing buffer conditions?

• Covalent bonding via multipoint attachment
• Physical adsorption to supports via weak interactions
• Cross-linking of enzyme aggregates (CLEAs)
• Entrapment within covalently cross-linked polyacrylamide

Correct Answer: Physical adsorption to supports via weak interactions

Q13. What is the main purpose of introducing a spacer arm between an enzyme and a solid support during covalent immobilization?

• To increase the molecular weight of the support
• To reduce steric hindrance and improve substrate accessibility to the active site
• To make the support hydrophobic
• To cause irreversible enzyme denaturation

Correct Answer: To reduce steric hindrance and improve substrate accessibility to the active site

Q14. Multipoint covalent attachment of an enzyme to a support commonly leads to which outcome?

• Decreased thermal and operational stability
• Increased susceptibility to proteolysis
• Improved structural rigidity and enhanced stability
• Complete loss of catalytic specificity

Correct Answer: Improved structural rigidity and enhanced stability

Q15. What is a key advantage of immobilized whole-cell biocatalysts compared with immobilized isolated enzymes?

• They eliminate the need for cofactor regeneration because the cell can regenerate cofactors
• They always provide higher specific activity per gram of biomass
• They never suffer from mass transfer limitations
• They allow enzyme purification to be skipped in all cases

Correct Answer: They eliminate the need for cofactor regeneration because the cell can regenerate cofactors

Q16. How does immobilization generally affect the thermal stability of an enzyme?

• Always decreases thermal stability because the support absorbs heat
• Often increases thermal stability by restricting conformational mobility
• Has no effect on thermal stability
• Causes enzymes to denature at room temperature

Correct Answer: Often increases thermal stability by restricting conformational mobility

Q17. In biosensor design, why are immobilized enzymes preferred for the recognition element?

• They provide single-use disposable devices only
• They are less specific than free enzymes
• They improve stability, allow repeated measurements, and localize the catalytic response
• They always eliminate the need for transducers

Correct Answer: They improve stability, allow repeated measurements, and localize the catalytic response

Q18. How does increasing the pore size of a porous carrier typically affect immobilized enzyme performance?

• Decreases enzyme loading and increases diffusion limitation
• Increases enzyme loading and reduces diffusion limitations for large substrates
• Makes carriers electrically conductive
• Always denatures the immobilized enzyme

Correct Answer: Increases enzyme loading and reduces diffusion limitations for large substrates

Q19. Which amino acid residue on many enzymes is most commonly targeted for covalent coupling to activated supports?

• Methionine sulfur atoms
• Lysine amino groups
• Tryptophan aromatic rings
• Selenocysteine residues

Correct Answer: Lysine amino groups

Q20. What is a practical way to quantify operational stability of an immobilized enzyme preparation?

• Measuring the theoretical isoelectric point of the support
• Measuring retained activity after defined numbers of reaction cycles or over continuous time (residual activity/half-life)
• Counting the number of covalent bonds formed per enzyme molecule
• Measuring only the initial activity without reuse

Correct Answer: Measuring retained activity after defined numbers of reaction cycles or over continuous time (residual activity/half-life)

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