IB skill practice

Model membrane dynamics and transport energetics

Paper 1, Paper 2 5 marks Difficulty 5

Explain cotransport logic

A transport diagram in a HL enzyme kinetics workshop shows sodium moving down its gradient through a carrier while glucose moves into the cell against its gradient. Explain the energy coupling. Use the diagram labels, HL model, or quantitative image evidence before answering. Enter the answer and choose the interpretation that best matches the HL biological evidence.

Worked practice: biological evidence and answer

Use the labelled biological evidence first, then connect it to the final answer.