IGCSE Biology Movement in & out of cells topical questions

Name the process described in each sentence.

1. (a)Oxygen moves from the alveoli of the lungs into the blood, down its concentration gradient.[1]
2. (b)Water moves from a dilute solution to a concentrated solution through a partially permeable membrane.[1]
3. (c)Mineral ions are taken up from dilute soil into a root hair cell, using energy from respiration.[1]

A student places a cube of purple-dyed agar into a beaker of water at 25 °C.

1. (a)State the name of the process that spreads the dye out of the cube.[1]
2. (b)State one way to make the dye spread faster.[1]
3. (c)The dye spreads even though nothing stirs the water. Explain why.[2]

The role of water in the body.

1. (a)State why digested food molecules must dissolve in water before they can be absorbed.[1]
2. (b)Name the solution in which waste products such as urea travel out of the body.[1]
3. (c)Name the liquid in blood that transports dissolved substances around the body.[1]
4. (d)State the process by which water enters root hair cells.[1]

Red blood cells are placed in three different liquids: pure water, a liquid with the same concentration as the cell contents, and a concentrated salt solution.

1. (a)Describe what happens to a red blood cell in pure water, and name the process.[2]
2. (b)State what happens to a red blood cell in the concentrated salt solution.[1]
3. (c)Plant cells become turgid in pure water, but animal cells burst. Explain why.[2]

Dialysis tubing is tied at both ends, filled with concentrated sugar solution and weighed. It is then left in a beaker of pure water for one hour and weighed again.

1. (a)Predict whether the tubing gains or loses mass, giving a reason.[2]
2. (b)State one property of dialysis tubing that makes it a model for a cell membrane.[1]
3. (c)The experiment is repeated in a 20% sugar solution instead of water. Predict and explain the result.[2]

Potato strips of identical size are left for one hour in different liquids. Their lengths are recorded.

1. (a)Calculate the percentage change in length for the strip in distilled water.[2]
2. (b)Calculate the percentage change in length for the strip in 10% salt solution.[2]
3. (c)Explain the change in length of the strip in 10% salt solution.[2]

Four beakers each contain a plant cell in a different solution.

1. (a)For each beaker, state the direction of net water movement (in, out, or no net movement).[2]
2. (b)Name the state of the cell in beaker A after five minutes.[1]
3. (c)Name and describe the state of the cell in beaker D after one hour.[2]

Three agar cubes of different sizes are cut and placed in red dye. Their dimensions and surface areas are given in the table.

1. (a)Calculate the surface area and volume of a 3 cm cube.[2]
2. (b)Complete the surface area to volume ratio for all three cubes, giving each ratio as a number.[2]
3. (c)Use the ratios to state which cube takes up dye fastest by diffusion, and explain why.[2]

A sealed bag made of dialysis tubing contains 20% sugar solution and has a mass of 10.0 g. It is left in a beaker of 30% sugar solution for one hour, then reweighed at 8.5 g.

1. (a)Calculate the percentage change in mass. Show your working and give the sign.[2]
2. (b)Explain the direction of the water movement that caused this change.[2]
3. (c)Predict and explain the change in mass if a second, identical bag is left in pure water for the same time.[2]

The factors that influence the rate of diffusion are investigated using cubes of dyed agar.

1. (a)Name the four factors that influence the rate of diffusion.[2]
2. (b)Explain two features that make a leaf well adapted for diffusion of gases.[2]
3. (c)State what happens to the rate of diffusion if the concentration gradient is doubled and nothing else changes.[1]
4. (d)Name the source of energy for diffusion.[1]

A farmer grows tomatoes in a glasshouse. On a hot day the leaves wilt; after watering, the leaves stand upright again.

1. (a)Explain why the leaves wilt on a hot day, using the words transpiration, osmosis and turgor.[3]
2. (b)Explain why the roots cannot simply absorb ions faster by leaving them to diffuse in.[2]
3. (c)The farmer adds fertiliser to dry soil by mistake, making the soil solution very concentrated. Predict what happens to the root cells and explain the effect on the plant.[1]

Two agar blocks of identical size contain 1% dye. Block P is placed in water at 10 °C; block Q in water at 35 °C. After 30 minutes the dye has spread 3 mm from block P but 8 mm from block Q.

1. (a)Calculate the average rate of dye spread from block Q, in mm per minute.[2]
2. (b)Calculate how many times faster the dye spread from Q than from P.[2]
3. (c)Explain the effect of temperature on the rate of diffusion.[2]
4. (d)State the energy source that powers this spreading.[1]

The glucose concentration in the blood is often higher than the glucose concentration in the contents of the small intestine, yet glucose continues to be absorbed into the blood.

1. (a)Define active transport.[2]
2. (b)Explain why glucose absorption must use active transport rather than diffusion.[2]
3. (c)Name the membrane structures that move the glucose molecules.[1]
4. (d)State where the cell gets the energy for this process.[1]
5. (e)Give one example of active transport in a plant, and state why it is needed there.[1]

Potato strips of identical size are placed in salt solutions of different concentrations for one hour. The percentage changes in length are shown.

1. (a)Describe the trend shown by the data.[2]
2. (b)Identify the range of salt concentrations within which no change in length would occur. Give a reason.[2]
3. (c)Explain why the strip in 0% salt solution gets longer.[2]
4. (d)State one improvement to the method that would make the results more reliable.[1]