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?

  It 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.
• What type of process is diffusion?

  It is an entirely passive process.
• How does temperature affect diffusion?

  The higher the temperature, the faster the particles can move by diffusion.

  
• What surrounds all cells?

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

  Because not all substances can diffuse across it.

  
• Which substances can diffuse across the cell membrane during gas exchange?

  Oxygen and carbon dioxide.

  
• What happens to urea produced by liver cells?

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

  A concentration gradient existing between the cell and its environment.

  
• How does the concentration gradient affect diffusion?

  If the direction of the concentration gradient changes, the movement of a substance by diffusion will also change.
• What happens to carbon dioxide concentration in a photosynthesising leaf cell on a bright day?

  It is likely lower compared to its environment.

  
• What is the effect of increasing the size of an organism on the surface area to volume ratio?

  As the size of an organism increases, the surface area to volume ratio decreases.

  
• What adaptations do multicellular organisms have for diffusion?

  • Exchange surfaces and transport systems
  • Increased surface area in specialized cells
  • Thin barriers for short diffusion paths
• How does the small intestine adapt for absorption?

  It has a highly folded surface to increase surface area.
• What role do alveoli play in the lungs?

  They facilitate gas exchange between air and blood.

  
• How are gills adapted for gas exchange in fish?

  They have a dense capillary network and are covered in lamellae to increase surface area.

  
• What is the role of root hair cells in plants?

  To absorb water and mineral ions from the soil.

  
• How do stomata help in gas exchange in leaves?

  They allow air to circulate inside the leaf, decreasing diffusion distance.
• What are the key features of effective exchange surfaces in multicellular organisms?

  • Large surface area
  • Thin barriers for short diffusion paths
  • Good blood supply to maintain concentration gradients
• What is osmosis in biology?

  It is the diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane.

  
• What happens to water during osmosis?

  Water moves from a more dilute solution to a more concentrated solution.

  
• What is the effect of solution concentration on diffusion?

  Identify which solution is more concentrated and which is more dilute to determine water movement.

  
• How can the movement of water by osmosis be observed?

  By placing two similar pieces of plant tissue in different solutions.

  
• What is osmosis?

  A special type of diffusion involving the movement of water molecules

  
• How do water molecules move during osmosis?

  Water molecules move randomly like any other particle that can diffuse
• In which direction does water move during osmosis?

  From a more dilute solution to a more concentrated solution

  
• What should you identify to determine the movement of water by osmosis?

  Which solution is more concentrated and which is more dilute

  
• What is the effect of osmosis on plant tissue?

  • Water moves into plant tissue from a dilute solution, causing it to gain mass.
  • Water moves out of plant tissue into a concentrated solution, causing it to lose mass.
  • No net movement occurs when concentrations are equal.

  
• What is commonly used in osmosis experiments to observe water movement?

  Potatoes

  
• What happens if plant tissue gains mass during an osmosis experiment?

  Water has moved into the plant tissue from a more dilute solution

  
• What does it indicate if plant tissue loses mass?

  Water has moved out of the plant tissue into a more concentrated solution
• What does no overall change in mass indicate in an osmosis experiment?

  There has been no net movement of water
• What is the aim of the osmosis required practical?

  • Investigate the effect of different concentrations of salt or sugar solutions on plant tissue mass.
  • Measure mass and length before and after soaking.
  • Calculate percentage change in mass.
• What should be prepared for the osmosis practical?

  Samples of potatoes or other plant tissue
• What is the independent variable in the osmosis practical?

  The concentration of salt or sucrose solution
• What is the dependent variable in the osmosis practical?

  The mass and length of each potato cylinder