68. In a gel filtration chromatography:
A. The large protein will be eluted first
B. The small protein will be eluted first
C. Both large and small will elute at the same time
D. The small protein with high charge will be eluted first
The correct answer is A. The large protein will be eluted first.
Gel filtration chromatography separates proteins by size, where larger proteins cannot enter the pores of the beads and elute faster, while smaller ones take longer paths through the pores.
Option Explanations
A. The large protein will be eluted first follows the core principle of size exclusion—large molecules are excluded from bead pores and travel the shortest path through the column.
B. The small protein will be eluted first confuses gel filtration with other methods like ion exchange; small proteins enter pores and elute later due to longer diffusion paths.
C. Both large and small will elute at the same time ignores size-dependent separation; elution volumes differ based on accessible stationary phase volume.
D. The small protein with high charge will be eluted first mixes principles—gel filtration is size-based only, charge affects ion exchange or electrophoresis.
Gel Filtration Basics
Gel filtration chromatography large protein eluted first defines this size-based separation technique essential for GATE Life Sciences. Large proteins exit first as they bypass bead pores, unlike smaller ones that delay inside.
Separation Mechanism
Beads like Sephadex contain pores with exclusion limits (e.g., G-25: 5-25 kDa). Large proteins (>exclusion limit) flow between beads (void volume), eluting at Ve = V0. Small proteins diffuse into pores, increasing path length: Ve = V0 + Kd(Vt-V0).
Option Analysis Table
| Option | Elution Principle | Correct? | GATE Trap |
|---|---|---|---|
| A | Large first (size exclusion) | Yes | Core concept |
| B | Small first | No | Confuses with other methods |
| C | Simultaneous | No | Ignores Kd variation |
| D | Charge-based | No | Wrong technique |
Exam Relevance
This PYQ tests fundamental vs. distractor knowledge. Remember: “large first” distinguishes gel filtration from electrophoresis (charge/mass) or ultracentrifugation (density).
