1. Key Concepts: Diffusion, Osmosis & Active Transport

Question 1

What are the ways that substances can move in and out of Cells?

Answer 1

Diffusion

Osmosis

Active transport

Question 2

What is Diffusion?

Answer 2

Gradual movement form high concentration to a low concentration

Happens in liquids and gases - this is because particles are able to move about more freely

Very small molecules can diffuse through cell membranes e.g. glucose, amino acids, water and oxygen - big molecules e.g. starch and proteins can fit through membrane

Question 3

What is Osmosis?

Answer 3

Net movement of water molecules across a partially permeable membrane (PPM) - from higher water concentration to a lower water concentration

Water molecules move both ways across PPM - as water molecules are able to move randomly

More water molecules on one side of PPM - steady net flow of water molecules into the lower concentration

Solute solution gets more dilute

Question 4

What is Active Transport?

Answer 4

Works against a concentration gradient

Movement of particles across membrane - against concentration gradient- lower to higher - using energy transferred during respiration

Requires energy