Diffusion & active transport

• What are the two main processes for substances moving in and out of cells?

  Diffusion and active transport
• What is diffusion?

  Movement of particles from high to low concentration
• What is the fancy definition of diffusion?

  Net movement from higher to lower concentration
• What are the functions of cell membranes?

  • Allow substances to enter and exit the cell
  • Facilitate diffusion, active transport, and osmosis
  • Permit only small molecules to diffuse (e.g., glucose, amino acids, water)
  • Prevent large molecules (e.g., starch, proteins) from passing
• What types of molecules can diffuse through cell membranes?

  Very small molecules like glucose and water
• How do particles move through the cell membrane?

  From higher concentration to lower concentration
• What is active transport?

  Movement of particles from low to high concentration
• How does active transport differ from diffusion?

  Active transport moves against a concentration gradient
• What does active transport require to function?

  Energy released by respiration
• How does active transport work in the digestive system?

  • Nutrients move from gut to blood
  • Diffusion occurs when nutrient concentration is higher in the gut
  • Active transport occurs when nutrient concentration is lower in the gut
  • Prevents starvation by allowing nutrient absorption
• What happens when there is a higher concentration of nutrients in the gut?

  Nutrients diffuse into the blood
• Why is active transport important for nutrient absorption?

  It allows nutrient uptake against concentration gradient
• What is the overall goal of diffusion in the context of this study material?

  Movement of information into the brain
• What is the mark allocation for the question about diffusion and active transport?

  3 marks