Movement of substances in and out of cells

Diffusion

The movement of molecules from a region of higher concentration to a region of lower concentration

What does diffusion allow living organisms to do?

• gain nutrients in the digestive system

• Gain oxygen in the lungs

• Remove waste products in the lungs and kidneys

Osmosis

The movement of water molecules from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane

Why is a partially permeable membrane required for osmosis?

Prevents the movement of larger molecules (e.g sugars) but allow the movement of smaller water molecules

Active Transport

The movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration

Why is energy needed for Active Transport?

Particles are being moved against a concentration gradient

Factors that affect diffusion

• surface area to volume ratio

• Distance

• Temperature

• Concentration gradient