Diffusion and Active Transport

• Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
• Diffusion is a passive process, meaning no energy is required
• Diffusion continues until particles are evenly distributed
• In diffusion, particles move down a concentration gradient. This means that particles with a higher concentration move down a concentration gradient and particles with a lower concentration move up a concentration gradient.
• An example of diffusion in biology is gaseous exchange, where there is a net movement of oxygen from the lungs into the blood and a net movement of carbon dioxide from the blood to the lungs
• Only small molecules such as amino acids, water and oxygen can pass through the cell membrane. Big molecules like starch or proteins cannot
• Active transport is the movement of particles across a membrane against a concentration gradient (from an area of low to high concentration) using ATP released during respiration
• Plants use active transport to get minerals they need from the soil, as plants need nitrate ions to create proteins. There is normally a lower concentration of nitrate ions in soil surrounding the roots
• Active Transport in the digestive system:

  • In the small intestine, carbohydrates are broken down into glucose
  • Glucose is then transferred into the blood stream through active transport, against a concentration gradient
• Active transport is an active process, as it requires energy

  Energy is required for active transport as it is against a concentration gradient, ATP is used as energy