1.2 Transport across cell membranes Flashcards
What is diffusion?
The movement of a substance from a high concentration to a low concentration along a concentration gradient.
What is the cell membrane composed of?
(Phospho)lipids and proteins.
What enters and leaves the cell by diffusion?
Oxygen, carbon dioxide, food and waste
What does the cell membrane do?
Controls the passage of substances into and out of the cell.
How is the cell membrane described?
Selectively permeable. Only has small pores which allows small substances through but not large molecules.
What is osmosis?
The diffusion of water across a membrane.
What happens when an animal cell is placed in a more concentrated solution?
Water moves from the high concentration in the cell to the low concentration outside the cell along a concentration gradient. The cell shrinks.
What happens when an animal cell is placed in a less concentrated solution(pure water)?
Water moves from a high concentration in the solution to the low concentration in the cell along a concentration gradient. The cell swells and bursts.
What happens when a plant cell is placed in a more concentrated solution?
Water moves from a high concentration inside the cell to a low concentration in the solution along a concentration gradient. The cell becomes plasmolysed. The vacuole shrinks and the membrane comes away from the cell wall.
What happens when a plant cell is placed in a less concentrated solution (pure water)?
Water moves from a high concentration in the solution to a low concentration in the cell along a concentration gradient. The cell becomes turgid. Vacuole and cell swell.
What is passive transport?
Movement of a substance with a concentration gradient which requires no energy.
Are diffusion and osmosis passive or active?
Passive.
What is active transport?
The movement of a substance against a concentration gradient which requires energy.
What are required for active transport?
Membrane proteins.
Which substance are moved by active transport?
Ions.
