Immobilization techniques for plant cells and secondary metabolite production MCQs With Answer

Introduction

Immobilization techniques for plant cells are powerful tools in medicinal plant biotechnology to enhance production of valuable secondary metabolites. This blog provides M. Pharm students with focused multiple-choice questions covering principles, matrices (alginate, kappa-carrageenan, polyacrylamide), methods (entrapment, adsorption, covalent binding, cross-linking), bioreactor designs, mass transfer issues, and strategies to improve yields such as elicitation and co-immobilization. Questions emphasize practical considerations for scale-up, cell viability, kinetic changes, and downstream processing. These MCQs are designed to deepen conceptual understanding and prepare students for examinations and research applications in optimizing immobilized plant cell systems for pharmaceutical compound production.

Q1. Which of the following is the most common method used to immobilize plant cells for secondary metabolite production?

• Entrapment in calcium alginate beads
• Adsorption onto metal surfaces
• Covalent binding to glass beads
• Embedding in dry cellulose powder

Correct Answer: Entrapment in calcium alginate beads

Q2. Immobilization of plant cells commonly improves secondary metabolite production primarily because it:

• Eliminates the need for nutrients
• Enhances cell stability and enables prolonged production
• Increases cell division rate dramatically
• Prevents transport of metabolites out of cells

Correct Answer: Enhances cell stability and enables prolonged production

Q3. A major disadvantage of immobilized plant cell systems is:

• Improved resistance to shear stress
• Enhanced mass transfer of oxygen and substrates
• Diffusional limitations leading to gradients within the matrix
• Unlimited reusability without productivity loss

Correct Answer: Diffusional limitations leading to gradients within the matrix

Q4. Which matrix property is most critical to minimize diffusional limitations for immobilized plant cells?

• High cross-link density and very small pore size
• Low porosity and hydrophobicity
• Appropriate pore size and high porosity for mass transfer
• Rigid crystalline structure to prevent swelling

Correct Answer: Appropriate pore size and high porosity for mass transfer

Q5. Cross-linking of cells using agents like glutaraldehyde primarily results in:

• Physical entrapment without chemical modification
• Covalent linking of cell surface groups to a matrix, potentially reducing viability
• Instant increase in cell proliferation
• Complete elimination of diffusion barriers

Correct Answer: Covalent linking of cell surface groups to a matrix, potentially reducing viability

Q6. Which immobilization technique is least likely to damage plant cell viability?

• Covalent binding with strong aldehyde cross-linkers
• Entrapment in mild alginate gels gelled with Ca2+
• Exposure to high concentrations of organic solvents during immobilization
• Direct covalent coupling to activated synthetic polymers

Correct Answer: Entrapment in mild alginate gels gelled with Ca2+

Q7. In an immobilized plant cell bioreactor, the term “effective diffusivity” refers to:

• The rate of cell division inside the matrix
• The diffusion coefficient of a solute through the immobilization matrix accounting for porosity and tortuosity
• The speed of gel formation during immobilization
• The electric conductivity of the matrix

Correct Answer: The diffusion coefficient of a solute through the immobilization matrix accounting for porosity and tortuosity

Q8. Which bioreactor configuration is commonly used for immobilized plant cell cultures to allow medium renewal and minimize shear?

• Stirred tank reactor with high-speed impeller
• Packed-bed or fixed-bed reactor
• Bubble column with vigorous sparging
• Rotating drum with abrasive surfaces

Correct Answer: Packed-bed or fixed-bed reactor

Q9. Co-immobilization of plant cells with elicitors or microbial cells aims to:

• Prevent any metabolic interactions and keep cells isolated
• Enhance elicitor-mediated induction of secondary metabolism and improve yields
• Reduce the availability of precursors for secondary metabolite synthesis
• Guarantee complete sterilization of the culture

Correct Answer: Enhance elicitor-mediated induction of secondary metabolism and improve yields

Q10. Which of the following is a commonly used synthetic polymer for immobilization of plant cells besides alginate?

• Polyacrylamide
• Polyethylene glycol as a dry powder
• Cellulose acetate membrane in solid state
• Polystyrene beads without surface modification

Correct Answer: Polyacrylamide

Q11. Immobilization often changes observed kinetics of production. A typical change is:

• Zero effect on apparent reaction rates
• Apparent Michaelis-Menten Km unaffected but Vmax always increases
• Apparent substrate affinity (Km) may increase due to mass transfer resistance and apparent Vmax may decrease
• Complete elimination of substrate inhibition phenomena

Correct Answer: Apparent substrate affinity (Km) may increase due to mass transfer resistance and apparent Vmax may decrease

Q12. Which parameter should be optimized to maintain oxygenation in immobilized plant cell cultures?

• Light intensity only
• Agitation or medium flow rate and matrix porosity to improve oxygen transfer
• Matrix color and opacity
• Amount of antibiotic in medium

Correct Answer: Agitation or medium flow rate and matrix porosity to improve oxygen transfer

Q13. The main role of elicitors in immobilized plant cell systems is to:

• Serve as carbon sources for cell growth
• Induce stress-related pathways that upregulate secondary metabolite biosynthesis
• Break down the immobilization matrix
• Act as antibiotics to prevent contamination

Correct Answer: Induce stress-related pathways that upregulate secondary metabolite biosynthesis

Q14. For downstream recovery of secondary metabolites from immobilized cells, which approach is frequently used?

• Exhaustive washing with organic solvents without concern for cell viability
• In situ product removal by adsorption (resins) or permeabilization combined with gentle extraction
• High temperature sterilization to release intracellular products
• Mechanical grinding of beads in the production vessel

Correct Answer: In situ product removal by adsorption (resins) or permeabilization combined with gentle extraction

Q15. Which assessment is most appropriate to evaluate viability of immobilized plant cells during a long-term run?

• Measuring only bead mechanical strength
• Staining methods (e.g., TTC), metabolic activity assays, and periodic release counts from beads
• Measuring pH alone
• Counting total dry weight of beads irrespective of cell status

Correct Answer: Staining methods (e.g., TTC), metabolic activity assays, and periodic release counts from beads

Q16. Which factor most directly determines the choice between entrapment and covalent immobilization for plant cells?

• Color of secondary metabolite
• Need to preserve cell viability versus need for mechanical stability and prevention of washout
• Price of growth medium only
• Ambient room humidity

Correct Answer: Need to preserve cell viability versus need for mechanical stability and prevention of washout

Q17. Immobilized plant cell cultures can be advantageous for scale-up because they:

• Always require smaller reactors than suspension cultures
• Allow repeated or continuous operation with reduced risk of cell washout and easier product separation
• Prevent the need for sterile operation entirely
• Eliminate oxygen requirements

Correct Answer: Allow repeated or continuous operation with reduced risk of cell washout and easier product separation

Q18. When comparing alginate and kappa-carrageenan gels for immobilization, a key difference is:

• Alginate requires monovalent cations to gel, while kappa-carrageenan uses calcium
• Kappa-carrageenan forms thermoreversible gels and alginate forms ionically cross-linked gels with divalent cations
• Both are chemically identical and interchangeable in all cases
• Kappa-carrageenan is hydrophobic while alginate is completely non-porous

Correct Answer: Kappa-carrageenan forms thermoreversible gels and alginate forms ionically cross-linked gels with divalent cations

Q19. Which analytical monitoring strategy is most useful to detect internal diffusion limitations in immobilized cell beads?

• Measuring only bulk substrate concentration
• Profiling concentration gradients inside beads via microelectrodes or sectioning and localized assays
• Observing bead color with naked eye only
• Measuring atmospheric CO2 above the reactor

Correct Answer: Profiling concentration gradients inside beads via microelectrodes or sectioning and localized assays

Q20. A common strategy to improve productivity of immobilized plant cell systems without harming viability is to:

• Increase cross-linker concentration to the maximum
• Optimize bead size, matrix porosity, and apply intermittent elicitation or in situ product removal
• Use high concentrations of organic solvents in the medium
• Completely eliminate aeration to reduce shear

Correct Answer: Optimize bead size, matrix porosity, and apply intermittent elicitation or in situ product removal

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