Sec 3 Biology Movement of Substances topical questions

Define diffusion.

Define osmosis.

State one role of diffusion in gas exchange in humans and one in flowering plants, naming the gases involved.

Soil water contains fewer nitrate ions than a root hair cell’s sap. Name the process that takes up nitrate and state what powers it.

For each situation, name the transport route used and the direction of movement: (a) water when the surrounding solution is more dilute than the cell sap; (b) oxygen when the blood carries less oxygen than the alveolar air; (c) mineral ions when the soil solution is more dilute in ions than the root sap.

A plant cell is placed first in distilled water and then, separately, in a concentrated salt solution. Explain what happens in each case.

Potato strip P rises from 5.0 g to 5.5 g; strip Q falls from 4.8 g to 4.4 g. Calculate the percentage change in mass of each strip.

Calculate the surface-area-to-volume ratios of 1 cm and 3 cm cubes, and use them to explain why large organisms need exchange surfaces.

Late in a meal, the gut lumen contains less glucose than the epithelial cells of the villi. Name the process that still absorbs glucose and explain how it works.

Strip P rises from 4.6 g to 5.1 g in a dilute solution; strip Q falls from 5.2 g to 4.5 g in a concentrated solution. Calculate the percentage change in mass of each strip and state in each case whether water entered or left the tissue.

Explain why oxygen always diffuses from the alveoli into the blood, but glucose must be absorbed by active transport late in a meal when the gut holds less glucose than the blood.

A student plots the percentage change in mass of potato strips against the concentration of the sugar solutions they soaked in. Describe the shape of the expected graph and explain the meaning of the point where the line crosses the concentration axis.

Design an investigation to find how sugar concentration affects osmosis in potato strips. State the variables and outline the method.

Explain why an animal cell bursts in pure water while a plant cell placed in the same water survives.

Three identical potato strips are soaked for 30 minutes: strip A gains 10% mass, strip B gains 2%, strip C loses 12%. Arrange the solutions in order of water potential and explain which solution is closest in concentration to the potato sap.

Explain, in terms of water potential, why a potted plant wilts when the soil dries out and recovers after watering.

A student has three drinks of unknown sugar concentration and must rank them using potato strips. Describe the method, the calculation, and how the results identify the most concentrated drink.

A root absorbs 36 mg of nitrate in 3 hours at 15 °C. When the temperature rises to 25 °C it absorbs 20 mg in 40 minutes. Calculate both uptake rates in mg per hour and state how many times faster uptake is at 25 °C.