Transport Across Membranes (SQA National 5 Biology): Exam Questions

The concentration of some ions within the cell sap of seaweed, the surrounding seawater, and a unicellular organism were measured.

The results are shown in the bar chart.

(i) Name the ion that moves from the seaweed into the seawater by diffusion and give a reason for your choice.

[2]

Ion............................................................................................................................

Reason.....................................................................................................................

(ii) The unicellular organism must always have a sodium ion concentration below 0.25 mg/L.

Name the process that moves excess sodium ions out of the unicellular organism.

[1]

The cell sap of the seaweed was tested to measure the concentration of each ion.

Name the structure in seaweed cells that contains cell sap.

The diagrams represent the movement of molecules across a cell membrane.

Which cell would require the greatest number of mitochondria to allow the movement shown?

A group of students measured the mass of pieces of turnip tissue before placing them in different concentrations of salt solution. After one hour, the change in mass of the turnip tissue was recorded.

The results are shown in the table.

Predict the percentage change in mass in a 2 g/100 cm³ salt solution.

...........................%

Identify the salt solution where most of the turnip cells would be turgid.

...................................g/100 cm³

The pieces of turnip used in this investigation all had a starting mass of 6 g.

Calculate the final mass of the piece of turnip in the 8 g/100 cm³ of salt solution.

................................................g

Four equal sized cubes of potato were weighed and each placed into a different concentration of sugar solution. They were dried and weighed again after one hour.

The results are shown in the table.

Which solution had the highest sugar concentration?

Plants transport water and mineral ions from their roots to the leaves.

Mineral ions can move from the soil to the root cells by active transport.

Describe the process of active transport.

Water enters a plant by osmosis, which is an example of passive transport.

(i) State what this means in terms of the energy required for osmosis.

[1]

(ii) Name the vessels that transport water to the leaves.

[1]

(iii) When water enters a plant cell the vacuole fills and swells until no more water can enter.

State the term used to describe a plant cell in this state.

[1]

The diagram shows a plant cell after being placed in a liquid for 30 minutes.

This cell has become:

The following statements relate to the transport of molecules across membranes:

1. Energy is required.

2. Molecules move from an area of high concentration to an area of low concentration.

3. Membrane proteins are involved.

Which of the statements apply to active transport?

In an investigation into the effects of different solutions on plant cells, a beetroot cylinder was dried with a paper towel, weighed, and placed in a concentrated salt solution.

After 30 minutes, the beetroot cylinder was removed from the salt solution, dried and reweighed. It was then placed in water for 30 minutes, removed, dried and reweighed.

Which row in the table shows the most likely results?