Active transport Edexcel International GCSE Science (Double Award) revision
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In plain words
Diffusion only moves things downhill, from lots to few. Sometimes a cell needs to pull in something that is already more concentrated inside than outside, which is uphill. That takes energy, like pumping water up to a tank. It's called active transport.
Three things to know
- Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, against the concentration gradient, using energy from respiration.
- Carrier proteins in the membrane do the moving.
- Examples: root hair cells taking in mineral ions from the soil; the small intestine absorbing the last of the glucose.
Tips and tricks
- Two things separate it from diffusion: it goes against the gradient, and it needs energy from respiration.
- Cells that do a lot of active transport have many mitochondria, to supply the energy.
It lands in your notebook with its questions as flashcards.
Active transport: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What does active transport need that diffusion does not?
Moving against the gradient takes energy.
In which direction does active transport move particles?
It works against the concentration gradient.
Which cell uses active transport to take in mineral ions?
Ions are more concentrated inside the root than in the soil.
What carries particles across the membrane in active transport?
They sit in the membrane and use energy to move the particles.
Why do cells that carry out active transport have many mitochondria?
Mitochondria carry out aerobic respiration.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 6 marks. Write your answers on paper, then check them.
Active transport
Edexcel International GCSE Science (Double Award) 4SD0 · 6 marks · papermunch.org
Name ______________________________ Date ______________
State two ways in which active transport differs from diffusion.[2]
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It moves particles against the concentration gradient (from lower to higher concentration), and it needs energy from respiration.
Explain why root hair cells need active transport to take in nitrate ions.[2]
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The concentration of nitrate ions is higher inside the cell than in the soil water, so they cannot enter by diffusion.
A poison that stops respiration is added to a root. Explain why the root stops taking in mineral ions.[2]
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Active transport needs energy from respiration, and without respiration no energy is released.
Answers: Active transport
- 1. It moves particles against the concentration gradient (from lower to higher concentration), and it needs energy from respiration.
- 2. The concentration of nitrate ions is higher inside the cell than in the soil water, so they cannot enter by diffusion.
- 3. Active transport needs energy from respiration, and without respiration no energy is released.