CH2 Movement of Substances

• Diffusion


  Net movement of particles from a region of higher concentration to a region of lower concentration
• Osmosis


  Net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
• Active Transport


  Movement of particles from a region of lower concentration to a region of higher concentration with the assistance of a transport protein that requires cellular energy
• Diffusion


  1. There is a higher concentration of (name of substance) (type of particles: atoms / molecules / ions) in the (mixture 1) than (mixture 2)

  2. Therefore, (name of substance) (type of particles: atoms / molecules / ions) moved from (location of mixture 1) to (location of mixture 2) by diffusion
• Diffusion


  • There is a higher concentration of oxygen molecules in the inhaled air than in the blood stream
  • Therefore, oxygen molecules move from the alveolus of the lungs into the blood capillaries by diffusion
• Osmosis


  1. (solution 1) has a higher water potential than (solution 2)

  2. Therefore, water molecules moved from (location of solution 1) to (location of solution 2) through the (named partially permeable membrane) by osmosis
• Osmosis

  • The groundwater has a higher water potential than the cell sap of the root hair cells
  • Therefore, water molecules move from the soil into root hair cells through the partially permeable cell surface membrane by osmosis
• Active Transport


  1. There is a lower concentration of (name of substance) (type of particles: atoms / molecules / ions) in the (mixture 1) than (mixture 2)

  2. Therefore, (name of substance) (type of particles: atoms / molecules / ions) were absorbed from (location of mixture 1) to (location of mixture 2) by active transport
• Active Transport


  • There is a lower concentration of magnesium ions in the groundwater than in cell sap of the root hair cells
  • Therefore, magnesium ions were absorbed from the groundwater into the root hair cells by active transport
• Effects of osmosis on plant and animal tissues


  • Plant cell: turgid (when water potential of solution is higher), original state (when water potential is the same), flaccid / plasmolysed (when water potential is lower)
  • Animal cell: bursts (when water potential of solution is higher), original state (when water potential is the same), crenated (when water potential is lower)
• The cell surface membrane is made of two layers of fat molecules (lipid bilayer), creating a hydrophobic environment within the membrane

  
• Molecules that do not dissolve well in water pass through the cell membrane easily
• The transport proteins that transport glycerol, carbon dioxide, oxygen, and fatty acids through cell membranes generally do not require cellular energy to do so
• Substances and their respective absorption pathways


  • Water: osmosis
  • Glucose: osmosis
  • Amino acids: active transport
  • Glycerol: diffusion
  • Carbon dioxide: diffusion
  • Oxygen: diffusion
  • Fatty acids: diffusion