Biology A-Level
sigmoid curve
What sigmoid curve means in Biology A-Level, as defined for AQA.
Definitions of sigmoid curve
Exam boards and our study guides word this term in slightly different ways. Learn the version your board uses.
Check what you remember
Read the wording for your board, then hide it and explain sigmoid curve in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: AQA
The oxyhaemoglobin dissociation curve is S-shaped, plotting percentage saturation of haemoglobin against partial pressure of oxygen.
The dissociation curve explained by cooperative binding, with a shallow start, a steep middle section and a plateau.
Topics that use sigmoid curve
- Mass transport in animals (AQA A-Level)
Related terms
- affinity
- affinity for oxygen
- atrial systole
- Atrioventricular valves
- biconcave disc
- Biological drawing conventions
- Bohr effect
- Causation
Using sigmoid curve in the exam
Check the command word and mark scheme for your exact question. After comparing your explanation with the reference, use the term in an answer on the linked topic. This practice does not predict an exam mark.
Practise Biology questions
Create a free account to answer exam-style questions on this topic and get feedback on your answers.
Start free
All Biology A-Level termsA week of Premium from your first lesson · Then the free plan continues · No card, no charge