B3.2 Transport (Organisms): Practice Questions

• a.

  The cell gains water and becomes turgid.

• b.

  The cell undergoes active transport to balance water levels.

• c.

  The cell loses water and plasmolysis occurs.

• d.

  The cell membrane becomes fully permeable to solutes.

• a.

  Transpirational pull from the leaves creates a negative pressure potential, drawing sap upwards from the roots to the leaves via the phloem.

• b.

  Active transport of sucrose into the phloem at the source lowers its water potential, causing water to enter and create high pressure, driving sap towards the sink where sucrose is actively unloaded.

• c.

  Active transport of water into the phloem at the source creates a high pressure, pushing sap towards the sink where solutes are unloaded.

• d.

  Water potential gradient drives sap from source to sink, with water entering phloem at the sink and exiting at the source.

• a.

  The thin, flexible primary cell walls that allow for expansion.

• b.

  The presence of sieve plates that regulate the flow of sap.

• c.

  The use of companion cells to actively load water into the vessel.

• d.

  The presence of lignin in the cell walls.

• a.

  Their walls are one cell thick, providing a short diffusion distance, while hydrostatic pressure is highest at the arteriole end facilitating fluid exit.

• b.

  They contain valves to prevent backflow, maintaining a constant low pressure for solute diffusion.

• c.

  Their thick, muscular walls withstand high pressure, allowing rapid flow.

• d.

  Their large lumen minimizes resistance, ensuring high hydrostatic pressure at the venule end.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.