AQA GCSE Combined Science (8464), Higher tier · Biology › Cell biology › Transport in cells
Practise Active transport. 11 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Active transport moves substances against a concentration gradient, using energy from respiration. Questions ask you to explain examples in root hair cells and the gut, and to compare active transport with diffusion and osmosis.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
3
State what active transport isThe movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient.
4
State where the energy comes fromActive transport needs energy from respiration.
5
Describe two examples of active transportMineral ions from the soil into root hair cells; sugar from the gut into the blood.
6
Compare diffusion, osmosis and active transportCompare what moves, which way it moves relative to the concentration gradient, and whether energy is needed.
6
Explain why root hair cells have many mitochondriaMore respiration releases more energy for the active transport of mineral ions.
7
Explain how oxygen affects active transportLess oxygen means less aerobic respiration, so less energy is released and active transport slows.
Notes
What active transport is
Active transport moves substances from a more dilute solution to a more concentrated solution: against the concentration gradient.
It needs energy from respiration.
Cells that carry out a lot of active transport have many mitochondria, to release the energy needed.
Anything that reduces respiration, such as a lack of oxygen or a poison that stops respiration, reduces active transport. grade 7+
Examples
Root hair cells absorb mineral ions from very dilute solutions in the soil. The concentration of ions is usually higher inside the root hair cell, so diffusion would not bring them in.
Plants need mineral ions for healthy growth, e.g. nitrate ions to make proteins.
In the small intestine, sugar molecules are absorbed from a lower concentration in the gut into the blood, which has a higher sugar concentration.
The sugar is carried to cells and used for respiration.
Comparing the three processes
Diffusion: particles of a gas or solute; from higher to lower concentration; no energy needed.
Osmosis: water only; from a dilute to a concentrated solution, through a partially permeable membrane; no energy needed.
Active transport: substances such as mineral ions and sugar; from a dilute to a more concentrated solution (against the gradient); energy from respiration needed.
Water enters root hair cells by osmosis, while mineral ions enter by active transport.
Cheatsheet
Active transport: from a more dilute to a more concentrated solution (against the concentration gradient)
Needs energy from respiration
Root hair cells: absorb mineral ions from very dilute soil solutions
Small intestine: sugar absorbed from the gut (lower concentration) into the blood (higher concentration)
Many mitochondria = lots of active transport
Diffusion and osmosis are passive (no energy); active transport needs energy
How to answer each type of question
Give differences between active transport and diffusion
2 marks4
Compare the direction: against or down the concentration gradient.
Compare the energy: needed or not needed.
Write each point as a comparison.
Example. Root hair cells absorb nitrate ions from the soil by active transport. Give two ways in which active transport is different from diffusion.
Show the model answer
Active transport moves substances against the concentration gradient / from a dilute to a more concentrated solution, but diffusion moves them from higher to lower concentration (1). Active transport needs energy from respiration, but diffusion does not (1).
Explain why a cell has many mitochondria
2 marks6
Say that respiration happens in mitochondria and releases energy.
Link the energy to active transport of the named substance.
Example. Root hair cells contain many mitochondria. Explain why.
Show the model answer
Mitochondria are where aerobic respiration happens, releasing energy (1). The energy is needed for the active transport of mineral ions into the root hair cells (1).
Compare the three transport processes
3 to 4 marks6
Say what moves in each process.
Say which way it moves relative to the concentration gradient.
Say whether energy is needed, and give an example if there is a mark left.
Example. Compare diffusion and active transport. [4 marks]
Show the model answer
Both move substances into or out of cells across the cell membrane (1). Diffusion moves particles from a higher to a lower concentration, whereas active transport moves them from a lower to a higher concentration / against the gradient (1). Diffusion does not need energy, whereas active transport needs energy from respiration (1). For example, oxygen enters cells by diffusion, but mineral ions enter root hair cells by active transport (1).
Explain data on ion uptake
3 marks7
Identify the process: ions taken up against a gradient means active transport.
Link the variable (oxygen, temperature, poison) to respiration.
Link respiration to the energy available for active transport.
Example. Scientists measured how fast barley roots took up potassium ions. Roots in a solution bubbled with air took up ions five times faster than roots in a solution with no oxygen. Explain this result.
Show the model answer
Potassium ions are taken up by active transport (1). Active transport needs energy from respiration (1). With oxygen, the root cells carry out aerobic respiration, which releases more energy, so ions are taken up faster (1).
Shortcuts and memory tricks
'Active' = needs energy: like pushing a trolley uphill, against the gradient.
Two examples to learn: 'roots and guts' (mineral ions into root hairs, sugar from the gut into the blood).
See 'many mitochondria' in a question about absorbing something? Think active transport.
Where marks are lost
Forgetting to say 'against the concentration gradient' (or 'from dilute to more concentrated').
Saying mitochondria 'make energy'. They release energy by respiration.
Saying mineral ions are absorbed by osmosis. Water enters by osmosis; mineral ions enter by active transport.
Getting the direction the wrong way round: in active transport, substances move to where they are more concentrated.
Exam technique
In any 'explain' answer, use the phrases 'against the concentration gradient' and 'energy from respiration'.
For comparison questions, cover what moves, the direction, whether energy is needed, and an example.
In data questions, link anything that changes respiration (oxygen, temperature, a poison) to the energy for active transport.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Some substances enter cells by active transport.
(a) What is meant by active transport?[2]
(b) Which process needs energy from respiration? Tick (✓) one box.[1]
Active transport
Diffusion
Osmosis
Evaporation
(c) Name one type of substance that plant root hair cells absorb from the soil by active transport.[1]
Show the answer and mark scheme
(a)
movement of substances from a more dilute solution to a more concentrated solution / against a concentration gradient
using energy from respiration
(b)Answer: Active transport
(c)
mineral ions
Question 2Medium6 marks
Substances move into and out of cells by diffusion, osmosis and active transport.
(a) Give two differences between active transport and diffusion.[2]
(b) Give one similarity between osmosis and active transport.[1]
(c) After a meal, sugar molecules are absorbed from the small intestine into the blood. Explain why active transport is needed to absorb all of the sugar.[2]
(d) Give one use of the sugar absorbed into the blood.[1]
Show the answer and mark scheme
(a)
active transport needs energy from respiration, but diffusion does not
active transport moves substances from a dilute to a more concentrated solution / against the concentration gradient, but diffusion moves substances from a higher to a lower concentration
(b)
both move substances across (partially permeable) cell membranes
(c)
(as sugar is absorbed) the sugar concentration in the gut becomes lower than in the blood
so sugar cannot be absorbed by diffusion / must be moved against the concentration gradient
(d)
(cell) respiration
Question 3Hard6 marks
Substances move into and out of cells by diffusion, osmosis and active transport.
Describe how substances are transported into and out of cells by diffusion, osmosis and active transport. Explain the differences between the three processes. Use examples in your answer.[6]
Show the answer and mark scheme
diffusion is the net movement of particles from a higher to a lower concentration (down a concentration gradient)
e.g. oxygen diffuses into cells / carbon dioxide diffuses out of cells / urea diffuses from cells into the blood plasma
osmosis is the diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane
e.g. water enters root hair cells by osmosis
active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient)
active transport needs energy from respiration; diffusion and osmosis do not
e.g. mineral ions are absorbed into root hair cells / sugar is absorbed from the gut into the blood by active transport
osmosis involves only water; diffusion and active transport move dissolved substances / gases
Marked with levels of response: the full level descriptors are in the app.