Cellular Transport — Drills · Grade 10 Science

Chapter: Cells, Membranes & Exchange

What these drills covers

By the end of Cellular Transport you should be able to:

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: diffusion, osmosis, passive transport, facilitated diffusion, active transport, endocytosis, exocytosis, tonicity.

Problem 1

Diffusion moves particles
  1. from low to high concentration, using ATP
  2. from high to low concentration, without ATP
  3. only through protein pumps
  4. only in living cells
Answer and explanation

from high to low concentration, without ATP

Diffusion is net movement down a concentration gradient and requires no energy input from the cell. It occurs in non-living systems too.

Problem 2

A plant cell is placed in distilled water. Water will
  1. leave the cell, which shrinks
  2. enter the cell, which becomes turgid
  3. neither enter nor leave
  4. enter only if ATP is supplied
Answer and explanation

enter the cell, which becomes turgid

Distilled water is hypotonic to the cell's interior, so water moves in by osmosis until the cell wall's pressure balances it, leaving the cell turgid.

Problem 3

An animal cell with an internal solute concentration of 0.9 percent is placed in a 5.0 percent salt solution. By what factor is the external concentration greater?
Answer and explanation

5.56

5.0 / 0.9 ≈ 5.56 times greater, so the solution is strongly hypertonic and water leaves the cell.

Problem 4

Active transport differs from facilitated diffusion in that active transport
  1. uses a protein
  2. moves substances down a gradient
  3. requires an energy input such as ATP
  4. occurs only in plants
Answer and explanation

requires an energy input such as ATP

Both use proteins, but active transport moves a substance against its gradient and therefore needs an energy source.

Problem 5

Explain why a cell in an isotonic solution still exchanges water with its surroundings.
Answer and explanation

Isotonic means the concentrations are equal, so there is no net movement, not that movement stops. Individual water molecules continue to cross the membrane in both directions at equal rates, so the cell's volume stays constant while exchange continues. Describing equilibrium as "nothing happening" misstates what is occurring.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 6

Root cells accumulate potassium to a concentration far above that of the surrounding soil water. Name the transport process and state what the cell must supply.
Answer and explanation

Active transport through a membrane pump, because potassium is being moved against its concentration gradient. The cell must supply energy, normally by coupling the pump to ATP hydrolysis, and it must build the specific pump protein. Diffusion cannot account for accumulation against a gradient.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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