Movement of Substances Into & Out of Cells Practice Questions

Which of these best describes diffusion?

Put a cross ( ☒ ) in the box next to your answer.

☐ A the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane

☐ B the net movement of particles from an area of higher concentration to an area of lower concentration

☐ C the net movement of particles from an area of lower concentration to an area of higher concentration

☐ D the movement of particles against a concentration gradient using energy from respiration

Explain why oxygen moves from the blood into a respiring muscle cell by diffusion.

Name the waste gas that diffuses out of the muscle cell into the blood.

Complete the sentence about osmosis.

Osmosis is the net movement of water molecules from a dilute solution to a ............................... solution, through a ............................... membrane.

A sample of red blood cells is placed in a concentrated salt solution.

Describe what happens to these red blood cells.

The alga takes up potassium ions and nitrate ions from the pond water.

Explain how the data show that these ions are taken up by active transport and not by diffusion.

The alga contains a large number of mitochondria.

Explain how this helps the alga to take up ions.

The pond water around the alga becomes very low in oxygen.

Predict and explain the effect this has on the uptake of potassium ions by the alga.

The table compares three processes that move substances into and out of cells.

Complete the table.

Process	Substance moved	Direction relative to the concentration gradient	Energy from respiration needed?
diffusion	gases such as oxygen and carbon dioxide	...............................	no
osmosis	...............................	down the water concentration gradient	...............................
active transport	mineral ions and glucose	...............................	yes

Calculate the rate of diffusion of the dye at $40\ \mathrm{°C}$ in mm per minute.

rate = .............................................................. mm per minute

Explain why the dye diffuses further at $40\ \mathrm{°C}$ than at $10\ \mathrm{°C}$.

The student repeated the investigation at $20\ \mathrm{°C}$ using a dye solution that was four times more concentrated.

Predict and explain the effect this has on the distance the dye diffuses in $20$ minutes.

Give two variables that the student should have controlled in this investigation.

Calculate the percentage change in mass of the potato cylinder placed in the sucrose solution of concentration $0.6$.

percentage change in mass = .............................................................. %

Estimate the concentration of sucrose solution at which there would be no net change in the mass of a potato cylinder.

Explain your answer.

One cylinder from group B had a final mass of $2.96\ \mathrm{g}$ after being left in sucrose solution. Its percentage change in mass was $-7.5\ \%$.

Calculate the starting mass of this potato cylinder.

starting mass = .............................................................. g

Explain why the students plotted percentage change in mass rather than change in mass in grams.

Explain why the percentage change in mass levels off at the highest concentrations of sucrose solution.

A chef prepares a salad.

Lettuce leaves that have gone limp are placed in a bowl of pure water for $30$ minutes. They become firm and crisp again.

Later, a salad dressing containing a high concentration of salt is poured over the crisp lettuce leaves. After a few minutes the leaves become limp again.

Explain these observations in terms of the movement of water into and out of the lettuce cells.