# DBT JRF 2022 — Question 91

Exam: DBT JRF 2022 · Section: B · Topic: Bioprocess Engineering › Enzyme Immobilization & Diffusion · Difficulty: Medium

## Question

If an enzyme is NOT damaged during the process of entrapment in a bead, then internal pore diffusion will:

## Options

- **A.** Change the observed $V_{max}$ only
- **B.** Change the observed $K_m$ only
- **C.** Change both the $V_{max}$ and $K_m$
- **D.** Both the observed $V_m$ and $K_m$ will remain unchanged

## Answer

Option B

## Explanation

Effect of enzyme entrapment on apparent Km and Vmax: Entrapment immobilises enzymes within a gel matrix (e.g., alginate, polyacrylamide beads). This creates a DIFFUSION BARRIER: Effect on kinetic parameters: 1. Apparent $K_M$ INCREASES: Substrate must diffuse through the gel matrix to reach the enzyme. Higher [S] is needed externally to maintain adequate substrate concentration at the active site (overcomes the diffusion barrier). So more substrate is required for half-maximal rate → $K_M^{app} > K_M^{free}$ . 2. Apparent $V_{max}$ DECREASES: The maximum rate is limited because not all enzyme active sites are accessible to substrate at high [S] due to diffusion limitations. Even saturating external [S] may not saturate all active sites within the bead. Both $K_M$ and $V_{max}$ are affected by entrapment immobilisation. Answer: Entrapment increases apparent Km (diffusion barrier limits substrate access) and decreases apparent Vmax.

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