Cellular Transport — Practice · Grade 10 Science

Chapter: Cells, Membranes & Exchange

What this practice covers

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

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

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

Problem 1

Osmosis is best defined as the diffusion of ___ across a selectively permeable membrane.
  1. protein
  2. water
  3. oxygen
  4. glucose
Answer and explanation

water

Osmosis specifically refers to the movement of water across a selectively permeable membrane toward the side with more solute.

Problem 2

Which is TRUE of active transport but NOT of passive transport?
  1. It never uses proteins
  2. It only moves water
  3. It requires energy (ATP) and can move substances against their concentration gradient
  4. It moves substances down their concentration gradient
Answer and explanation

It requires energy (ATP) and can move substances against their concentration gradient

Active transport spends energy to move substances against the gradient; passive transport moves them down the gradient for free.

Problem 3

A red blood cell is placed in pure (hypotonic) water. What happens?
  1. Water leaves and the cell shrivels
  2. Nothing changes
  3. The cell builds a cell wall
  4. Water enters by osmosis and the cell swells and may burst
Answer and explanation

Water enters by osmosis and the cell swells and may burst

Pure water is hypotonic, so water rushes in by osmosis; with no wall to resist, the animal cell swells and can burst (lysis).

Problem 4

Explain the difference between endocytosis and exocytosis.
Answer and explanation

In endocytosis, the membrane wraps around material and pulls it into the cell inside a vesicle (bringing things in). In exocytosis, a vesicle fuses with the membrane and releases its contents outside the cell (sending things out). Both move large amounts of material and require energy.

Problem 5

The sodium-potassium pump ejects 3 sodium ions and imports 2 potassium ions each cycle. What is the net number of positive charges moved OUT of the cell per cycle?
Answer and explanation

1 charges

3 positive charges leave and 2 positive charges enter, so the net is 3 − 2 = 1 positive charge moved out.

Problem 6

Why must fluids given through an IV drip be isotonic to a patient's blood?
  1. So there is no net osmosis — the blood cells neither swell and burst nor shrivel
  2. So the cells absorb as much water as possible
  3. So the cells lose water quickly
  4. Because isotonic fluids contain no water
Answer and explanation

So there is no net osmosis — the blood cells neither swell and burst nor shrivel

An isotonic fluid matches the solute concentration of blood, so water moves in and out equally and red blood cells keep their normal shape.

Problem 7

A cell is placed in an equal-pressure solution containing more impermeant solute than its interior. Predict initial water movement. Explain the reasoning in your own words.
Answer and explanation

The cell initially loses water; the final behavior also depends on cell structure and pressure.

The external solution has the higher effective solute concentration.

Water moves out in the simple osmosis model.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 8

A cell pumps ions against their gradient. What distinguishes this from facilitated diffusion? Show the reasoning, not just the conclusion.
Hints

State permeability and effective solute conditions; not every solute is trapped.

Answer and explanation

The pump uses coupled energy; facilitated diffusion moves particles down their electrochemical gradient.

Problem 9

Why can a plant cell resist bursting in dilute surroundings better than many animal cells?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Its cell wall resists expansion, allowing turgor pressure to balance water entry.

Problem 10

Transport proteins can support passive or energy-driven movementTransport proteins can support passive or energy-driven movementFacilitated diffusion: down-gradientAn active pump can use energy to move against its driving gradient.Using a protein does not by itself make transport active.
Original facilitated transport schematic. The protein symbolizes a route, not a measured ion pump, ATP stoichiometry or complete electrical gradient.
Interpret the supplied visual. Would a saturating uptake curve alone distinguish facilitated diffusion from active transport?
Answer and explanation

No. Both can have limited protein capacity; gradient direction and energy coupling provide additional tests.

Facilitated diffusion uses a channel or carrier for down-gradient transport. Active transport couples energy transfer to movement against the relevant driving gradient, directly through ATP or indirectly through another gradient. Primary active transport uses a direct energy source; secondary transport can use a gradient maintained by other processes. A pump and a passive carrier can both become saturated as capacity is limited. Therefore, protein involvement or a plateau alone does not establish whether the step is active; use direction, gradients, coupling and controlled energy perturbations.

No. Both can have limited protein capacity; gradient direction and energy coupling provide additional tests.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 11

A tissue sample changes from 12 g to 9 g in a stated nonpenetrating-solute model. Find percentage change and explain a suitable osmotic account plus one measurement control.
Answer and explanation

The change is −3/12×100 = −25%. Net water loss is consistent with a hypertonic external solution under the model. Comparable blotting, membrane integrity and limits on solute loss are needed before assigning all mass change to water.

The change is −3/12×100 = −25%. Net water loss is consistent with a hypertonic external solution under the model. Comparable blotting, membrane integrity and limits on solute loss are needed before assigning all mass change to water.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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