Simple diffusionPassive: no energy is spent. Oxygen and carbon dioxide cross this way, down their concentration gradient.
Facilitated diffusionPassive: no energy is spent. Ions and glucose move down their gradient through a channel or a carrier protein.
OsmosisPassive: water moves toward the side with less free water. That is the side with more dissolved material.
Channel proteinIts water-filled channel lets one kind of ion through the membrane. The ion does not touch the lipid core.
Carrier proteinIt binds a substance such as glucose. It changes shape and lets it go on the other side.
AquaporinAquaporins let water through the membrane at a very high rate.
Concentration gradientA difference in the concentration of a substance across a space. Passive transport runs down it, from high to low.
Active: energy spent 6
Active transportActive: a pump protein moves a substance against its concentration gradient. That takes the cell's energy.
ATPAdenosine triphosphate. Active transport usually takes its energy from ATP. The sodium-potassium pump is the textbook example.
PhagocytosisTakes in large particles, even whole cells, in a vesicle. A kind of endocytosis. Active: it takes energy.
PinocytosisTakes in fluid and the molecules in it, in a small vesicle. A kind of endocytosis. Active: it takes energy.
Receptor-mediated endocytosisReceptor proteins bind a specific substance. The coated pit pinches in as a vesicle. Active: it takes energy.
ExocytosisA vesicle fuses with the plasma membrane. It releases its contents outside the cell. The reverse of endocytosis. Active: it takes energy.
How this list was compiled: Every name, and whether each route is passive or active, checked on 2026-09-30 against OpenStax Biology 2e, sections 5.2 Passive Transport, 5.3 Active Transport and 5.4 Bulk Transport (https://openstax.org/books/biology-2e/pages/5-2-passive-transport, https://openstax.org/books/biology-2e/pages/5-3-active-transport, https://openstax.org/books/biology-2e/pages/5-4-bulk-transport), and against Wikipedia, Passive transport, Active transport, Endocytosis, Exocytosis and Aquaporin, text only. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
A biology cell transport quiz on two drawings. The first shows the routes through a strip of membrane; the second shows bulk transport, where the membrane itself wraps the cargo.
Read the full guide
Passive or active: read the arrows
On the first drawing the wedge runs from high to low. Four routes follow it and spend no energy: simple diffusion between the lipids, facilitated diffusion through a channel or a carrier protein, and osmosis, which is water through an aquaporin. The pump on the right moves its cargo the other way, from few to many, and spends ATP: that is active transport. On the second drawing all four scenes are active. Three bring material in (endocytosis) and one sends it out (exocytosis).
No protein and no energy: simple diffusion. A protein but no energy: facilitated diffusion.
Phagocytosis is cell eating and pinocytosis is cell drinking.
Questions and answers
What are the types of cell transport?
Passive transport spends no energy: simple diffusion, facilitated diffusion and osmosis. Active transport spends the cell's energy: pumps that move a substance against its gradient, and bulk transport by endocytosis and exocytosis.
What is the difference between passive and active transport?
Passive transport moves a substance down its concentration gradient, from high to low, and needs no energy. Active transport moves it against the gradient, from low to high, and needs energy, usually from ATP.
What is the difference between endocytosis and exocytosis?
Endocytosis brings material into the cell: the membrane folds round it and pinches off as a vesicle. Exocytosis is the reverse: a vesicle fuses with the membrane and releases its contents outside.
Is osmosis passive or active transport?
Passive. Osmosis is the diffusion of water across a membrane, and it spends no energy. Much of the water passes through channel proteins called aquaporins.