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IB Biology SL B2.1 Membranes and Membrane Transport Questions

Practise IB Biology SL B2.1 by linking membrane structure and selective permeability to diffusion, osmosis, transport proteins and ATP-driven active transport.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Identify amphipathic phospholipid bilayers, explain head–tail orientation in water and relate the hydrophobic core to selective barriers and compartment separation.
  • Define simple diffusion as passive net movement down a concentration gradient without ATP or transport proteins, including small non-polar molecules crossing the bilayer.
  • Distinguish integral and peripheral membrane proteins and identify their channel, pump, receptor, enzyme, adhesion and recognition roles.
  • Define osmosis, predict water movement from solute or water-potential differences and explain how aquaporins increase water permeability.
  • Explain facilitated diffusion through selective channel proteins as passive movement down a gradient, using size, charge and polarity to explain selectivity.
  • Explain active transport as ATP-powered movement against a concentration gradient using selective pump proteins.
  • Identify glycoproteins and glycolipids as membrane components carrying extracellular carbohydrate chains and relate them to cell recognition and adhesion.
  • Use the fluid mosaic model to locate hydrophilic heads, hydrophobic tails, integral proteins and mobile membrane components in a selective membrane.

Covered syllabus points

B2.1.1—Lipid bilayers as basisB2.1.2—Bilayers as barriersB2.1.3—Simple diffusionB2.1.4—Integral and peripheral proteinsB2.1.5—Osmosis and aquaporinsB2.1.6—Channel proteinsB2.1.7—Pump proteinsB2.1.8—Selectivity in permeabilityB2.1.9—Glycoproteins and glycolipidsB2.1.10—Fluid mosaic model

Question 1

[Maximum number: 3]

The diagram shows the stages of the cell cycle.

Figure for Question 1 — IB Biology SL

Explain the properties of phospholipids that allow bilayers to form in cell membranes.

Question 2

[Maximum number: 4]

Question (a)

(a)

Outline how molecules move across a membrane by simple diffusion.

[ 2 ]

Question (b)

(b)

Explain the role of protein pumps in active transport.

[ 2 ]

Question 3

[Maximum number: 2]

List two functions of membrane proteins.

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