AQA GCSE Biology B3

Summary Notes

Entering Cells

• Osmosis is the movement of water from a dilute concentration to a concentrated solution.
• Water enters root hair cells by osmosis.
• Animal cells burst in a dilute concentration, because too much water enters by osmosis.
• Plant cells don't burst in a dilute concentration because of the cell wall.
• Cells shrink if they are placed into a concentrated solution because water leaves by osmosis.
• Osmosis needs a partially permeable membrane.
• Diffusion and osmosis are passive, so happen without energy.
• Active transport requires energy.
• Active transport goes against the concentration gradient.
• Alveoli are needed to get oxygen into the blood and carbon dioxide out of the blood.
• Exchange surfaces are adapted for efficient diffusion.

Getting Around

• Ventilation exchanges gases in the lungs.
• The diaphragm and rib muscles are needed for ventilation.
• The heart pumps blood around the body.
• Arteries carry blood away from the heart…