Biology · Form and function

B2.1 — Membranes and membrane transport

Biology · SL / HL · syllabus-mapped notes

1. B2.1.1

   Lipid bilayers as the basis of cell membranes

   Explain how amphipathic lipids form continuous sheet-like bilayers in water.

2. B2.1.2

   Lipid bilayers as barriers

   Explain why the hydrophobic core blocks large molecules, ions and polar molecules.

3. B2.1.3

   Simple diffusion across membranes

   Explain simple diffusion using oxygen and carbon dioxide moving between phospholipids.

4. B2.1.4

   Integral and peripheral proteins in membranes

   Distinguish integral from peripheral proteins by where they sit in the membrane.

5. B2.1.5

   Movement of water molecules across membranes by osmosis and the role of aquaporins

   Explain osmosis in terms of random motion, solute concentration and impermeability, plus aquaporins.

6. B2.1.6

   Channel proteins for facilitated diffusion

   Explain how channel proteins make a membrane selectively permeable, and how gating changes it.

7. B2.1.7

   Pump proteins for active transport

   Explain how pump proteins use ATP to move particles against the concentration gradient.

8. B2.1.8

   Selectivity in membrane permeability

   Explain why facilitated diffusion and active transport are selective, but simple diffusion is not.

9. B2.1.9

   Structure and function of glycoproteins and glycolipids

   Describe glycoproteins and glycolipids, and their roles in cell adhesion and cell recognition.

10. B2.1.10

    Fluid mosaic model of membrane structure

    Draw the fluid mosaic model, labelling proteins, phospholipids, cholesterol and the hydrophobic region.

11. B2.1.11

    Relationships between fatty acid composition of lipid bilayers and their fluidity

    Explain how saturated and unsaturated fatty acids change fluidity, with an example adapted to habitat.

12. B2.1.12

    Cholesterol and membrane fluidity in animal cells

    Explain where cholesterol sits, and how it modulates fluidity at both high and low temperatures.

13. B2.1.13

    Membrane fluidity and the fusion and formation of vesicles

    Explain endocytosis and exocytosis as consequences of membrane fluidity, with examples of each.

14. B2.1.14

    Gated ion channels in neurons

    Explain neurotransmitter-gated and voltage-gated ion channels in neurons.

15. B2.1.15

    Sodium–potassium pumps as an example of exchange transporters

    Explain the sodium-potassium pump as an exchange transporter, and how it generates membrane potentials.

16. B2.1.16

    Sodium-dependent glucose cotransporters as an example of indirect active transport

    Explain sodium-dependent glucose cotransport in the small intestine and the nephron.

17. B2.1.17

    Adhesion of cells to form tissues

    Explain how cell-adhesion molecules bind cells into tissues.