Describe how body temperature is measured using a clinical thermometer and explain why maintaining a normal core body temperature is important for the body to function correctly.

AQA A-Level Physics (7408) — 3.10.3 Biological Measurement · Describe and Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

A clinical thermometer is placed in contact with the body – for example under the tongue, in the armpit or in the ear – so that the mercury or alcohol column can respond to the body’s heat. The thermometer is then read and the value compared with the normal core body temperature of about 37 °C.

Maintaining a core temperature of ~37 °C is essential because most enzymes in the body have an optimum temperature around this value. If the temperature rises or falls, enzyme activity decreases, enzymes may become denatured and the rate of chemical reactions slows. A temperature far above or below 37 °C can be life‑threatening, signalling illness and requiring medical treatment.

Examiner tips

  • Use the exact wording ‘under the tongue / in the armpit / in the ear’ to show you know the common sites.
  • Mention the normal core temperature (≈37 °C) and link it to enzyme optimum.
  • Explain the effect of temperature on enzyme activity and the consequences of deviation.
  • Show that a large deviation can be life‑threatening or indicate illness.

Common mistakes

  • Writing only one placement site (e.g. only ‘under the tongue’) and omitting the others.
  • Forgetting to state the normal core temperature of 37 °C.
  • Failing to explain that enzymes have an optimum temperature and that deviation reduces activity.

Mark scheme (5 marks)

  1. The thermometer is placed in contact with the body (e.g. under the tongue / in the armpit / in the ear) to measure temperature
  2. The thermometer reading is compared to the normal core body temperature of approximately 37 °C
  3. Enzymes in the body work best / are most active at normal body temperature (optimum temperature)
  4. If temperature is too high or too low, enzyme activity is reduced / enzymes are denatured / chemical reactions in the body slow down
  5. A temperature significantly above or below 37 °C can be life-threatening / indicates illness / requires medical treatment

Key terms in this question

core body temperature · clinical thermometer

Related

More Biological Measurement questions

▶ Try answering this question with AI marking (free) →