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IB Biology HL B2.1 Membranes and Membrane Transport Questions

Practise IB Biology HL B2.1 with membrane diagrams and data questions covering selective permeability, transport mechanisms, fluidity, vesicles and ion pumps.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Identify amphipathic phospholipid bilayers, explain head–tail orientation in water and relate the hydrophobic core to membrane 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, transmembrane and peripheral 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 by ATP-powered pumps, including sodium–potassium movement against gradients and the resulting ion gradients or resting potential.
  • Identify membrane glycoproteins and glycolipids with extracellular carbohydrate chains and relate the glycocalyx to recognition, adhesion and signalling.
  • Use the fluid mosaic model to locate hydrophilic heads, hydrophobic tails, embedded proteins and mobile membrane components, distinguishing it from the sandwich model.
  • Relate unsaturated and saturated fatty-acid composition and cholesterol to membrane packing, permeability, fluidity and temperature stability.
  • Explain how membrane fluidity permits vesicle budding, transport and fusion, and distinguish endocytosis from exocytosis.
  • Distinguish voltage-gated from ligand-gated ion channels and relate channel opening, membrane potential and potassium movement to nerve impulses.
  • Explain sodium-dependent glucose cotransport as secondary active transport driven by a sodium gradient maintained by basolateral pumps, including intestinal absorption.

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 modelB2.1.11 (HL)—Fatty acid composition and fluidityB2.1.12 (HL)—Cholesterol and fluidityB2.1.13 (HL)—Membrane fluidity and vesiclesB2.1.14 (HL)—Gated ion channels in neuronsB2.1.15 (HL)—Sodium-potassium pumpsB2.1.16 (HL)—Sodium-glucose cotransportersB2.1.17 (HL)—Cell adhesion molecules (CAMs)

Question 1

[Maximum number: 3]

Question (a)

(a)

Outline how the amphipathic properties of phospholipids play a role in membrane structure.

[ 2 ]

Question (b)

(b)

State the role of cholesterol in animal cell membranes.

[ 1 ]

Question 2

[Maximum number: 1]

Neural pathways in living brains can now be mapped by tracking the movement of water molecules inside axons. What keeps water molecules inside axons?

A

Plasma membrane

B

Hydrogen bonding

C

Pump proteins

D

Synapse

Question 3

[Maximum number: 1]

Which process results in the exchange of gases across the membrane of pneumocytes?

A

Active transport

B

Simple diffusion

C

Facilitated diffusion

D

Mass flow

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