Transport

• What is the definition of diffusion?

  Diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration.
• What does the term "net" mean in the context of diffusion?

  "Net" refers to the overall movement of particles.
• Which three molecules move in and out of cells by diffusion?

  • Oxygen
  • Carbon dioxide
  • Urea
• Why do cells need oxygen?

  Cells need oxygen for respiration, which is carried out by mitochondria.
• How does the concentration of oxygen outside the cell compare to that inside the cell?

  The concentration of oxygen is higher outside the cell than inside the cell.
• What happens to oxygen molecules when they move into the cell?

  Oxygen molecules move from an area of higher concentration to an area of lower concentration by diffusion.
• What is produced as a waste gas during respiration?

  Carbon dioxide is produced as a waste gas during respiration.
• How does the concentration of carbon dioxide inside the cell compare to that outside the cell?

  The concentration of carbon dioxide is higher inside the cell than outside.
• How does urea move out of cells?

  Urea diffuses out of the cells into the blood plasma and is excreted by the kidneys.
• What are the three main factors that affect the rate of diffusion?

  1. Difference in concentrations (concentration gradient)
  2. Temperature
  3. Surface area of the membrane
• What is the concentration gradient?

  The concentration gradient is the difference in concentration between two areas.
• How does a greater concentration gradient affect diffusion?

  A greater concentration gradient results in faster diffusion.
• How does temperature affect the rate of diffusion?

  Higher temperature increases the rate of diffusion due to greater kinetic energy of particles.
• How does the surface area of the cell membrane affect diffusion?

  A larger surface area of the cell membrane increases the rate of diffusion.
• What is the relationship between surface area and diffusion rate in cells?

  • Larger surface area = greater rate of diffusion
  • Smaller surface area = slower rate of diffusion
• What is the process by which molecules move in and out of cells?

  Diffusion
• What happens to oxygen and carbon dioxide during diffusion in cells?

  Oxygen diffuses into cells and carbon dioxide diffuses out
• What happens to the surface area to volume ratio as organisms increase in size?

  The surface area to volume ratio decreases
• What are two adaptations animals have developed for gas exchange?

  Special structures with high surface area and a transport system
• What role do the filaments in fish gills play in gas exchange?

  They provide a large surface area for diffusion
• What is the significance of having a thin membrane in gill filaments?

  It provides a short diffusion path
• Why is an efficient blood supply important for gill filaments?

  It maintains a high concentration gradient for diffusion
• What are the adaptations of gill filaments that increase the rate of diffusion?

  • Surface area
  • Thin membrane for short diffusion pathway
  • Efficient blood supply to maintain concentration gradient
• What is the relationship between surface area to volume ratio and the need for exchange surfaces in multicellular organisms?

  • As size increases, surface area to volume ratio decreases
  • Larger organisms need specialized exchange surfaces
  • Diffusion alone is insufficient for gas exchange in larger organisms
• What is osmosis?

  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• How does osmosis differ from diffusion?

  Osmosis specifically refers to the movement of water, while diffusion refers to the movement of particles
• If a cell has a higher concentration of water outside than inside, what will happen to the cell?

  Water will move into the cell by osmosis
• What happens to an animal cell placed in pure water?

  The cell expands and may burst due to water moving in by osmosis
• What is the effect of osmosis on a plant cell placed in water?

  The plant cell becomes turgid and swells without bursting due to the cell wall
• What term is used to describe a plant cell that has become swollen due to osmosis?

  Turgid
• What happens to a plant cell in a concentrated solution?

  Water moves out of the cell, causing it to become flaccid
• Why does a plant cell not burst when it becomes turgid?

  The cell wall provides structural support and prevents bursting
• What are the key points about osmosis in animal and plant cells?

  • Osmosis is the diffusion of water through a partially permeable membrane.
  • In animal cells:
  • Water entering causes expansion and potential bursting.
  • Water leaving causes shrinking.
  • In plant cells:
  • Water entering causes turgidity without bursting due to the cell wall.
  • Water leaving causes flaccidity.
• What is the role of a partially permeable membrane in osmosis?

  It allows water molecules to pass through but not sugar molecules
• If a concentrated sugar solution is separated from a dilute sugar solution by a partially permeable membrane, what will happen to the water molecules?

  Water will diffuse from the dilute solution to the concentrated solution
• What is the concentration of water in a dilute solution compared to a concentrated solution?

  A dilute solution has a high concentration of water, while a concentrated solution has a low concentration of water
• How does the concentration of water affect the movement of water during osmosis?

  Water moves from areas of high concentration to areas of low concentration
• What is osmosis?

  Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What happens to a plant cell when it is placed in water?

  Water moves into the cell by osmosis, causing the cell to expand
• What occurs when a plant cell is placed in a concentrated solution?

  Water moves out of the plant cell by osmosis, causing the cell to shrink