細胞的物質運輸：練習題

Which process is defined as the spreading of particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration?

Active transport is a vital process in both plants and animals. Which of the following is a key characteristic of active transport?

A researcher treats a sample of plant root hair cells with a metabolic poison that prevents the mitochondria from performing aerobic respiration. The cells are placed in a solution where the concentration of magnesium ions (\(\text{Mg}^{2+}\)) is \(0.1\text{ mol/dm}^3\), while the concentration inside the cell sap is \(0.5\text{ mol/dm}^3\).

Which of the following correctly predicts the effect on the transport of \(\text{Mg}^{2+}\) ions and oxygen (\(\text{O}_2\)) across the cell membrane?

Which of these factors will increase the rate of diffusion of a substance into a cell?

Single-celled organisms rely on their surface area to volume ratio for the exchange of materials. As the size of an organism increases, what happens to this ratio?

Identify the process by which water moves from a dilute solution to a more concentrated solution across a partially permeable membrane.

Explain why active transport is necessary for plant root hair cells to absorb mineral ions from the soil.

Explain how the structure of the alveoli in the lungs, as shown in the diagram, is adapted to maximize the effectiveness of gas exchange.

A student investigated the effect of different concentrations of sugar solution on the mass of potato cylinders. The table below shows the results of the experiment:

Concentration of sugar solution (mol/dm³) | Percentage change in mass (%)
0.0 | +15.2
0.2 | +8.1
0.4 | -2.4
0.6 | -10.5

(a) Explain why the potato cylinder in the 0.0 mol/dm³ solution increased in mass.
(b) Use the data to estimate the concentration of the sugar solution that would be isotonic to the potato cell cytoplasm.
(c) State one variable that the student should have controlled to make this investigation valid.

The exchange of materials in organisms is affected by the surface area to volume ratio (SA:V).
(a) Calculate the SA:V ratio for a cube with a side length of \(2\) cm. Show your working.
(b) Explain why single-celled organisms do not need a specialised gas exchange system, while large multicellular organisms do.
(c) Describe how active transport differs from diffusion in terms of the concentration gradient and the requirement for energy.