Transport in Cells

• What is diffusion?


  Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
• What are the three main factors that affect the rate of diffusion?


  The three main factors are concentration gradient, temperature, and surface area.
• How are single-celled organisms adapted for diffusion?


  Single-celled organisms have a large surface area relative to their volume, facilitating efficient diffusion.
• Give examples of substances transported by diffusion in the lungs and the kidney.


  Oxygen and carbon dioxide in the lungs; urea and water in the kidney.
• How is surface area to volume calculated?


  Surface area to volume ratio is calculated by dividing the surface area by the volume.
• What are the four factors that increase the effectiveness of a gas exchange surface?


  • Large surface area
  • Thin walls
  • Moist surfaces
  • Good blood supply
• What is meant when a solution is isotonic to a cell?


  An isotonic solution has the same concentration of solutes as the cell, resulting in no net movement of water.
• What is osmosis?


  Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane.
• What is meant when a solution is hypertonic to a cell?


  A hypertonic solution has a higher concentration of solutes than the cell, causing water to leave the cell.
• What is meant when a solution is hypotonic to a cell?


  A hypotonic solution has a lower concentration of solutes than the cell, causing water to enter the cell.
• What may happen when an animal cell is placed in a very hypertonic solution?


  The animal cell may shrink or crenate due to loss of water.
• What may happen when an animal cell is placed in a hypotonic solution?


  The animal cell may swell and potentially burst due to excess water intake.
• How do plant leaves and stems remain rigid?

  Plant leaves and stems remain rigid due to turgor pressure from water in the vacuoles of plant cells.
• What may happen when a plant cell is placed in a very hypertonic solution?


  The plant cell may undergo plasmolysis, where the cell membrane pulls away from the cell wall due to water loss.
• How do plant root hair cells use active transport?


  Plant root hair cells use active transport to absorb minerals from the soil against the concentration gradient.
• What is active transport?


  Active transport is the movement of substances against their concentration gradient, requiring energy.
• How is active transport used to absorb the products of digestion?

  Active transport is used to absorb glucose and amino acids from the intestine into the bloodstream against their concentration gradient.