Ai generated shi

• Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient as a result of their random movement
• Factors influencing the speed of diffusion:

  • Substance concentration inside and outside the cell
  • Temperature
  • Surface area
  • Thickness of the cell wall
• Importance of diffusion to organisms:

  • Substances move into and out of cells by diffusion through the cell membrane
  • Reasons for diffusion: obtain raw materials, get rid of waste, gas exchange for respiration and photosynthesis, digestion
• Diffusion is a passive process, using energy from the kinetic energy of the random movement of molecules and ions

  • Diffusion can occur across a membrane or in a liquid or gas
• Active Transport:

  • Occurs when concentration is low outside the cell and high inside the cell but more needs to be absorbed
  • Examples: ion uptake by root hairs, uptake of glucose by epithelial cells of villi and kidney tubules
  • Movement of substances through a cell membrane from a low concentration to a high concentration against a concentration gradient, using energy from respiration
  • Carrier proteins in the cell membrane are used to move the molecules
• Water as a Solvent:

  • Water is important for all living organisms as many substances are able to dissolve in it
  • Water is a solvent, allowing easy transport of dissolved substances around organisms
  • Water plays a role in metabolic reactions and is essential for life on Earth
• Osmosis:

  • Water moves through partially permeable membranes from a high water potential to a low water potential
  • Osmosis in plant cells: effects of placing cells in pure water or low water potential solutions
  • Osmosis in animal cells: effects of placing cells in pure water or concentrated solutions
• Investigating osmosis in plants:

  • Experiment with potatoes using length
  • Design practical using mass
• Identifying solutions using visking tubing practical:

  • Hypotonic
  • Isotonic
  • Hypertonic
• Movement of water by plants:

  • Plants take water from the soil where there needs to be a higher concentration of water than in the roots
  • Water moves down a water potential gradient from high to low water potential