Biology-Osmosis

Selectively permeable membrane

Allows some but not all substances to pass through

Advantage of a selectively permeable membrane

Only certain substances are let in or out of cell

What cell components contain membranes and are selectively permeable?

Cell membrane, mitochondria, chloroplast, nucleus

Diffusion

When molecules move from an area of high concentration to an area of low concentration

Example of diffusion in the lungs

Oxygen diffuses from the alveoli into the capillary. Carbon dioxide and water vapour diffuses from capillary into the alveoli

Example of diffusion in the leaf

Carbon dioxide diffuses from the atmosphere into the leaf through the stomata. Oxygen diffuses from the leaf into the atmosphere.

Osmosis

The movement of water from a region of high water concentration to a region of low water concentration through a semi permeable membrane

Turgor pressure

Occurs when there is pressure of the cytoplasm and vacuole against the cell wall of a plant

Function of turgor pressure

Strength and support

Plasmolysis

When the plant cell loses water and the cell membrane moving away from the cell wall

Active transport

The movement of molecules against the gradient from an area of lower concentration to an area of higher concentration which requires energy

Passive transport

Does not require energy for the movement of molecules