B2

• what do particles in a gas or solution do constantly?

  move around
• what is diffusion?

  the net movement of particles from a region of high concentration to a region of low concentration
• what do particles move down in diffusion?

  a concentration gradient
• what is the concentration gradient when the concentration of the particles is the same everywhere?

  zero
• true or false ; energy is not transferred during diffusion, it is a passive process?

  True
• why does diffusion happen?

  because of the ordinary motion of the particles
• what do all cells need for respiration?

  glucose and oxygen
• how are glucose and oxygen transported around the body?

  in the blood
• how does glucose and oxygen get into the cells that need them?


  diffusion
• how do waste products leave cells after a chemical reaction?

  they diffuse out of the respiring cells
• what does the process of diffusion allow particles to do?

  enter and leave cells
• what do the particles pass through?

  the cell membrane
• which 3 factors affect the rate of diffusion?

  distance, concentration gradient and surface area
• how do you increase the rate of diffusion?

  -decrease the distance needed to be travelled by particles

  -increase the concentration gradient (the steeper the concentration gradient, the greater the net movement of particles)

  -increase the surface area (this allows more space for diffusion so more particles can move in a given time)
• what is osmosis?

  the diffusion of water molecules across a selectively permeable membrane
• what is a selectively permeable membrane?

  A membrane that allows certain substances to pass through while not allowing others
• what does osmosis do?

  explains how water enters and leaves cells
• what is water potential?

  the concentration of free water molecules
• what has the highest possible water potential?

  pure water, as all the water molecules are free to move
• what happens when a solution becomes more concentrated?

  the water potential lowers
• what is osmosis the movement of?

  water molecules from a high water potential to a low water potential (down a concentration gradient)
• what happens if there is a greater difference in water potential?

  there will be a greater rate of osmosis
• what is active transport?

  it allows cells to move substances from an area of low concentration to an area of high concentration
• what happens when particles are moving against their concentration gradient?

  energy must be transferred from an energy store
• what are 3 key features of active transport?

  -particles are transported (pumped) against a concentration gradient

  -ATP is required (comes from photosynthesis)

  -the process makes use of carrier proteins in the cell membrane
• what do cells that carry out a lot of active transport contain?

  many mitochondria
• what does having many mitochondria mean?

  cells can respire rapidly to produce lots of ATP
• what does the rate at which active transport occurs depend on?

  the rate of respiration to produce the needed ATP
• what are carrier proteins?

  they are special proteins that span the width of the cell membrane
• what do specific carrier proteins bind to?

  a particular molecule that the cell requires
• why is energy transferred to the carrier protein?

  so that it can change shape or rotate to transport the molecule into the cell
• what particular energy is used to allow the carrier protein to move the molecule into the cell?

  ATP
• when is active transport used?

  whenever a substance needs to be moved against a concentration gradient
• when is an example of when active transport is used?

  during digestion
• why do plants use active transport?

  to take in minerals from the soil
• what do plant root hair cells use active transport for?

  to move products across the cell membrane and into the root cell
• what is mitosis?

  when body cells divide to replace worn out cells, to repair damaged tissue and to enable the organism to increase in size
• what is the process of mitosis?

  when a cell divides to produce 2 identical daughter cells, these are genetically identical to the parent cell and are the exact clone
• what does mitosis increase the number of?

  cells in a multicellular organism
• what is the process of cell growth and division called?

  cell cycle