transport in cells

• What is necessary for any organism to function properly?


  It needs to exchange substances such as food molecules and waste products.
• Where does the exchange of substances occur in an organism?


  Across the cell membrane.
• What are the three transport processes used by living organisms for exchange?


  • Diffusion
  • Osmosis
  • Active transport
• What is diffusion?


  Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.
• What happens to particles in a solution or gas during diffusion?


  They are always moving about randomly.
• What is a simple example of diffusion?


  The diffusion of perfume particles through a room.
• Is diffusion a passive or active process?


  Diffusion is an entirely passive process.
• What affects the rate of diffusion?

  The kinetic energy of the particles, which is influenced by temperature.
• What happens to the rate of diffusion as temperature increases?


  The rate of diffusion increases.
• What surrounds all cells and separates them from their environment?

  A cell membrane.
• Why is the cell membrane described as partially permeable?


  Because some substances can enter or leave the cell while others cannot.
• Which substances can diffuse across the cell membrane during gas exchange?


  Oxygen and carbon dioxide.
• What must happen to urea produced by liver cells?


  It must diffuse out of cells to be excreted by the kidneys.
• What drives the movement of substances into and out of a cell by diffusion?


  A concentration gradient existing between the cell and its environment.
• How does the concentration of carbon dioxide in a photosynthesising leaf cell change during the day?


  It is likely lower than in the environment due to photosynthesis.
• What happens to the concentration of carbon dioxide in a leaf cell at night?


  It will be higher than in the environment due to respiration.
• What factors affect the rate of diffusion?


  • Concentration gradient
  • Temperature
  • Surface area
  • Distance
• How does the surface area to volume ratio affect diffusion in organisms?


  A higher surface area to volume ratio allows for easier exchange of substances.
• What is the relationship between the size of an organism and its surface area to volume ratio?


  As the size of an organism increases, the surface area to volume ratio decreases.
• Why do larger organisms need exchange surfaces and transport systems?


  • They have a relatively small surface area compared to their volume.
  • Diffusion alone cannot meet their needs.
• What is an example of a cell adapted for diffusion in plants?


  Root hair cells.
• How does the small intestine increase its surface area for absorption?


  It has a highly folded surface lined with specialized epithelial cells.
• What is the role of the alveolus in the lungs?


  Gas exchange between air in the alveoli and the blood.
• How is the structure of the alveolus adapted for gas exchange?


  It has a wall that is one cell thick and a moist lining with a good blood supply.
• What is the role of gills in fish?


  Gas exchange between water flowing through the gills and the blood.
• How do gills increase their surface area for gas exchange?


  Each gill is made from smaller plates called filaments covered in projections called lamellae.
• What is the role of root hair cells in plants?


  To absorb water and mineral ions from the soil.
• How do stomata in leaves facilitate gas exchange?


  They allow air to circulate inside the leaf, decreasing diffusion distance for gases.
• What adaptations do multicellular organisms have for efficient exchange of materials?


  • Large surface area to increase transport rate
  • Thin barriers to minimize diffusion distance
  • Extensive blood vessel networks
  • Well-ventilated gas exchange surfaces
• What is osmosis?


  The diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane.
• What is the significance of osmosis in biology?


  It regulates the movement of water into and out of cells.
• What must be identified to determine the movement of water by osmosis?


  Which solution is more concentrated and which is more dilute.
• What does osmosis specifically refer to?


  The movement of water molecules.
• How does water move during osmosis?


  From a more dilute solution to a more concentrated solution.
• What is the relationship between osmosis and diffusion?


  Osmosis is a special type of diffusion specifically for water molecules.
• What is the effect of solution concentration on diffusion?


  Water will move to equalize the concentration of water molecules on each side of the membrane.
• Why is it important to mention osmosis when discussing the movement of water in an exam?


  Because osmosis specifically refers to the movement of water molecules.
• What is the direction of water movement in osmosis?


  Water moves from a more dilute solution to a more concentrated solution.
• Why does water move during osmosis?


  To even up the concentration of water molecules on each side of the membrane.
• What does osmosis refer to?


  The movement of water molecules across a membrane.