Chapter 13: Diffusion and Osmosis

Permeable

substances can freely pass through the membrane

Selectively Permeable

allows some but not all substances to pass through

Impermeable

substances cannot freely pass in or out of the membrance

Diffusion

the movement of a substance from a high concentration to an area of low concentration

Passive Process

does not require energy

Biological Membranes

are selectively permeable, allows water, carbon dioxide, oxygen, doesn’t allow sugars, proteins, salts

Factors Affecting Diffusion

concentration of substances, temperature, size of molecules, surface area

Examples of Diffusion in Animals

gaseous exchange in the lungs, absorption of digested food from intestine into blood

Example of Diffusion in Plants

plant hormones are produced at the tips of the roots and shoots and move through the plant via diffusion, gaseous exchange in the leaf

Osmosis

the movement of water molecules across a selectively permeable membrane from a region of high water concentration to a region of low water concentration

Solvent

liquid that dissolves other substances

Solute

the substance that has been dissolved

Solution

mixture of solvent and solute

Cells in High Water Concentration

animal cells burst due to osmosis allowing too much water into the cell, plant cells become rigid

Haemolysis

blood cells bursting due to high water concentration

Cells in a Low Water Concentration

cells shrivel due to water loss

Crenation

red blood cells shrivelling due to low water concentrations

Plasmolysis

plant cells shrinking due to low water concentration

Preservation

osmosis is useful in food preservation as it removes water from organisms when they land on food as the food is covered in salt or sugar to reduce its water concentration