diffusion, osmosis, active transport

• What is the definition of diffusion?

  The movement of molecules from a region of higher concentration to a region of lower concentration

  
• What does it mean for molecules to move down a concentration gradient?

  Molecules move from areas of high concentration to areas of low concentration

  
• What is the result of the random movement of molecules in diffusion?

  The spreading out of molecules until they are at even concentration throughout the available space
• How do molecules move into or out of living cells?

  By diffusion when they cross the cell membrane
• What is the nature of the cell membrane in relation to diffusion?

  The cell membrane is partially permeable
• Why can smaller molecules diffuse across the cell membrane while larger molecules cannot?

  Because the cell membrane allows some molecules to cross but not others
• What are some examples of how diffusion is utilized in living organisms?

  To gain nutrients in the digestive system, gain oxygen in the lungs, and remove waste products in the lungs and kidneys
• What is the definition of osmosis?

  The movement of water molecules from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane

  
• How is osmosis related to diffusion?

  Osmosis is the diffusion of water molecules
• What happens to animal cells in a strong sugar solution?

  The cell loses water and becomes crenated (shriveled)
• What happens to animal cells in distilled water?

  The cell gains water and may burst
• How does osmosis affect plant cells in a strong sugar solution?

  The cell loses water, the vacuole shrinks, and the cell membrane pulls away from the wall, making the cell flaccid or plasmolysed

  
• What occurs in plant cells when they are placed in distilled water?

  The cell gains water, the vacuole expands, and the membrane pushes against the cell wall, making the cell turgid
• What is the role of turgid cells in plants?

  They provide structural support and prevent wilting
• What must be clear when describing osmosis?

  What type of concentration you are referring to, specifically water concentration
• What is the definition of active transport?

  The movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration

  
• Why is energy needed for active transport?

  Because particles are being moved against a concentration gradient

  
• What releases energy for active transport?

  Energy is released during cellular respiration
• What role do protein carrier molecules play in active transport?

  They facilitate the movement of particles across the cell membrane

  
• What are two examples of active transport in cells?

  Absorption of digestion products into the bloodstream and absorption of mineral ions from soil into root hair cells

  
• How does surface area to volume ratio affect diffusion?

  The bigger a cell or structure is, the smaller its surface area to volume ratio, slowing down diffusion
• What is an example of a cell adapted for diffusion?

  Root hair cells in plants
• How does the thickness of walls in blood capillaries and alveoli affect diffusion?

  Thinner walls ensure faster diffusion
• How does temperature affect the rate of diffusion?

  The higher the temperature, the faster molecules move
• What happens to the rate of diffusion with a greater concentration gradient?

  The faster the movement across the membrane will occur

  
• What factors influence the rate of diffusion?

  • Concentration gradient
  • Temperature
  • Surface area to volume ratio
  • Diffusion distance
• How can you investigate the effect of temperature on diffusion using beetroot?

  1. Cut equally-sized cubes of beetroot.
  2. Rinse to remove pigment.
  3. Place in water at different temperatures.
  4. Observe the color of the liquid after a set time.

  
• What happens to beetroot pigment when heated above 45℃?

  The pigment leaks out of the cell
• Why is it important for beetroot pieces to have equal surface areas and volumes in the experiment?

  To ensure that surface area and volume do not affect the rate of diffusion
• What can be concluded from observing the color of the liquid in the test tubes after the beetroot experiment?

  The rate of diffusion is affected by temperature

  
• What is the significance of the results from the beetroot diffusion experiment?

  It demonstrates how temperature affects the permeability of cell membranes

  
• What is the main focus of the investigation described in the study material?

  The effect of temperature on diffusion
• What apparatus is used in the investigation of temperature's effect on diffusion in beetroot?

  • Beetroot
  • Knife
  • Cork borer (optional)
  • Cutting board
  • Ruler
  • Test tubes
  • Water baths
  • Stopwatch

  
• How should the beetroot pieces be cut for the experiment?

  Into equally-sized cubes to ensure equal surface areas and volumes
• Why is it important for the beetroot pieces to have the same dimensions?

  To ensure they all have equal surface areas and volumes
• What should be done to the beetroot pieces before placing them in the test tubes?

  They should be rinsed to remove any pigment released during cutting
• What is the temperature of the water bath for test tube B?

  90℃
• What is observed after adding beetroot pieces to the test tubes?

  The color of the liquid in both test tubes after 10 minutes
• What is the expected result regarding pigment leakage at higher temperatures?

  More pigment will leak out at higher temperatures
• Why does more pigment leak out at higher temperatures?

  Because the cell membrane becomes damaged and particles have more kinetic energy