IGCSE Biology
2026 - 2028
Syllabus Checklist
Topic 3: Movement into and out of Cells
1. Diffusion
Describe diffusion
as the net movement of particles from a region of higher concentration to a region of lower concentration (down a concentration gradient
), as a result of their random movement.
State that the energy for diffusion comes from the kinetic energy
of randomly moving molecules and ions.
State that some substances move into and out of cells by diffusion
through the cell membrane
.
Describe the importance of diffusion
of gases and solutes in living organisms.
Investigate the factors that influence diffusion, limited to: surface area
, temperature
, concentration gradient
, and distance
.
2. Osmosis
Describe the role of water
as a solvent in organisms with reference to digestion
, excretion
, and transport
.
State that water
diffuses through partially permeable membranes
by osmosis
.
State that water moves into and out of cells by osmosis
through the cell membrane
.
Investigate osmosis using materials such as dialysis tubing
.
Investigate and describe the effects on plant tissues
of immersing them in solutions of different concentrations.
State that plants
are supported by the pressure of water
inside the cells pressing outwards on the cell wall
.
Describe osmosis
as the net movement of water molecules
from a region of higher water potential
(dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
.
Explain the effects on plant cells
of immersing them in solutions of different concentrations using the terms: turgid
, turgor pressure
, plasmolysis
, and flaccid
.
Explain the importance of water potential
and osmosis
in the uptake and loss of water by organisms.
3. Active Transport
Describe active transport
as the movement of particles through a cell membrane
from a region of lower concentration to a region of higher concentration (against a concentration gradient), using energy from respiration
.
Explain the importance of active transport
as a process for the movement of molecules or ions across membranes, including ion uptake by root hair cells
.
State that protein carriers
move molecules or ions across a membrane during active transport.
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