AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Active transport moves substances from a more dilute solution to a more…
Full specification wording
Active transport: Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient).
Active transport is the movement of substances across a cell membrane from a region of lower concentration to a region of higher concentration, that is, against a concentration gradient.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Active transport is the movement of substances across a cell membrane from a region of lower concentration to a region of higher concentration, that is, against a concentration gradient. This is the opposite direction to simple diffusion, which is passive and down a concentration gradient. Because active transport moves substances against the gradient, it requires energy and carrier proteins in the membrane. In plants, root hair cells use active transport to absorb mineral ions such as nitrate from soil, where the soil solution is more dilute than the cell cytoplasm. In animals, cells lining the small intestine use active transport to absorb glucose from the gut when gut concentration is lower than blood concentration. The process is selective because specific carrier proteins transport specific substances.
What earns the marks
- Define active transport as movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient.
- Contrast active transport with diffusion, which is passive and moves substances down a concentration gradient.
- State that active transport requires energy from respiration and carrier proteins in the cell membrane.
- Give a named example, such as root hair cells absorbing mineral ions from dilute soil solution.
- Explain that carrier proteins are specific, so active transport allows selective uptake of particular substances.
- Describe how the direction of movement relates to concentration: from lower concentration to higher concentration.
Common mistakes and how to put them right
Saying active transport moves substances from high to low concentration.
Put it right by stating it moves from more dilute to more concentrated, against the gradient.
Confusing active transport with osmosis.
Put it right by noting that osmosis is passive water movement, while active transport uses energy and carrier proteins.
Forgetting that active transport requires energy.
Put it right by linking it to respiration and ATP production in the cell.
Exam tips
- Use the phrase against a concentration gradient when defining active transport, as this distinguishes it from diffusion.
- When giving an example, name the substance and the direction of movement, such as mineral ions entering root hair cells from dilute soil solution.
- If asked to compare transport processes, make clear that active transport requires energy and carrier proteins, whereas diffusion does not.
Try the lesson
The start of the Active transport: Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). lesson, made from checked teaching notes for this specification point.
Have a go first
Which description matches active transport?
Listen
Active transport is the movement of substances across a cell membrane from a region of lower concentration to a region of higher concentration, that is, against a concentration gradient. This is the opposite direction to simple diffusion, which is passive and down a concentration gradient. Because active transport moves substances against the gradient, it requires energy and carrier proteins in the membrane. In plants, root hair cells use active transport to absorb mineral ions such as nitrate from soil, where the soil solution is more dilute than the cell cytoplasm. In animals, cells lining the small intestine use active transport to absorb glucose from the gut when gut concentration is lower than blood concentration. The process is selective because specific carrier proteins transport specific substances. A strong answer earns marks for these points. Define active transport as movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient. Contrast active transport with diffusion, which is passive and moves substances down a concentration gradient. State that active transport requires energy from respiration and carrier proteins in the cell membrane. Give a named example, such as root hair cells absorbing mineral ions from dilute soil solution. A common slip: Saying active transport moves substances from high to low concentration. Instead, stating it moves from more dilute to more concentrated, against the gradient. Exam tip: Use the phrase against a concentration gradient when defining active transport, as this distinguishes it from diffusion.
Key words
Say what each word means before you turn the card.
Active transport
Try answering aloud or in your head before turning the card.
Concentration gradients
Try answering aloud or in your head before turning the card.
Carrier proteins and selectivity
Try answering aloud or in your head before turning the card.
Energy requirements in cells
Try answering aloud or in your head before turning the card.
See every definition
- Active transport
- Movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient.
- Concentration gradients
- Active transport moves substances against a concentration gradient, from a more dilute solution to a more concentrated solution.
- Carrier proteins and selectivity
- Carrier proteins in the membrane are specific, so active transport allows selective uptake of particular substances.
- Energy requirements in cells
- Because substances are moved against the gradient, active transport requires energy from respiration.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Active transport: Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient).
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge