.3 active transport

• Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.
• Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth.
• It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
• how substances are transported into and out of cells by diffusion:

  a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane.
• how substances are transported into and out of cells by osmosis

  water molecules move from low solute concentration(high water concentration) to high solute or low water concentration across a membrane that is not permeable to the solute
• how substances are transported into and out of cells by active transport

  the substances move from a low concentration to a higher concentration
• the differences between diffusion, osmosis and active transport

  In diffusion and osmosis, substances move down a concentration gradient. However, active transport moves substances against a concentration gradient. Active transport is an active process, which means it requires energy from respiration