AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Cholesterol may also be present in cell membranes where it restricts the…
Full specification wording
Transport across cell membranes: Cholesterol may also be present in cell membranes where it restricts the movement of other molecules making up the membrane.
Cholesterol is a lipid that sits between phospholipid molecules in the cell membrane bilayer, binding to their fatty acid tails.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 3 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Cholesterol is a lipid that sits between phospholipid molecules in the cell membrane bilayer, binding to their fatty acid tails. By holding these tails together, it restricts the movement of phospholipids and other membrane molecules. This regulates membrane fluidity, preventing it from becoming too fluid at high temperatures and maintaining mechanical stability. This stability is crucial for animal cells, like red blood cells, which lack a supporting cell wall and must withstand being squeezed through capillaries. It also helps prevent the membrane from becoming too rigid at low temperatures.
What earns the marks
- Cholesterol is located between the phospholipids in the bilayer, binding to their fatty acid tails.
Common mistakes and how to put them right
Stating cholesterol makes the membrane stronger without explaining that it restricts molecular movement.
Placing cholesterol on the surface of the membrane rather than between the phospholipid tails.
Confusing membrane cholesterol with blood cholesterol and discussing atheroma and heart disease.
Exam tips
- Use the phrase 'restricts movement of molecules' when describing cholesterol's function in the membrane.
- Link cholesterol to its consequence: restricted movement regulates fluidity and provides stability.
Try the lesson
The start of the Transport across cell membranes: Cholesterol may also be present in cell membranes where it restricts the movement of other molecules making up the membrane. lesson, made from checked teaching notes for this specification point.
Have a go first
A student claims that the cholesterol present in a cell membrane increases the movement of the other molecules making up the membrane. Which statement best explains why this claim is incorrect?
Listen
Cholesterol is a lipid that sits between phospholipid molecules in the cell membrane bilayer, binding to their fatty acid tails. By holding these tails together, it restricts the movement of phospholipids and other membrane molecules. This regulates membrane fluidity, preventing it from becoming too fluid at high temperatures and maintaining mechanical stability. This stability is crucial for animal cells, like red blood cells, which lack a supporting cell wall and must withstand being squeezed through capillaries. It also helps prevent the membrane from becoming too rigid at low temperatures. Exam tip: Use the phrase 'restricts movement of molecules' when describing cholesterol's function in the membrane.
Key words
Say what each word means before you turn the card.
cholesterol between phospholipids
Try answering aloud or in your head before turning the card.
restricted phospholipid movement
Try answering aloud or in your head before turning the card.
membrane fluidity
Try answering aloud or in your head before turning the card.
mechanical stability
Try answering aloud or in your head before turning the card.
See every definition
- cholesterol between phospholipids
- A lipid that sits between phospholipid molecules in the cell membrane bilayer, binding to their fatty acid tails.
- restricted phospholipid movement
- The limiting of the movement of phospholipids and other molecules making up the membrane, caused by cholesterol holding the fatty acid tails together.
- membrane fluidity
- A property regulated by cholesterol, which prevents the membrane from becoming too fluid at high temperatures and from becoming too rigid at low temperatures.
- mechanical stability
- Support provided to membranes, especially in animal cells lacking a cell wall, which must withstand being squeezed through capillaries.
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 Transport across cell membranes: Cholesterol may also be present in cell membranes where it restricts the movement of other molecules making up the membrane.
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