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7.1 Hormones and coordination

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Question 12

A doctor measures the blood concentrations of thyroxine and TSH in a person on two occasions, 14 days apart. The results are shown in the table.

TimeThyroxine concentration (nmol/L)TSH concentration (mIU/L)
First measurement1002.4
14 days later700.8

Two explanations are suggested for the results:

  • the hypothalamus is releasing less TRH
  • the thyroid gland is responding less to TSH
a.

Explain which explanation is better supported by the measurements.

[3]
b.

Predict the effect of the change in thyroxine concentration on the person’s metabolic rate. Give a reason for your answer.

[2]
Markscheme

7.1 Hormones and coordination Questions

  1. GCSE
  2. /Biology
  3. /7.1 Hormones and coordination

89 exam-style questions on Edexcel GCSE Biology 7.1 Hormones and coordination, covering 7.1.1 Endocrine glands and hormone transport, 7.1.2 Adrenalin and fight or flight, and 7.1.3 Thyroxine and negative feedback. Each one has a worked solution and a mark scheme showing where the marks go.

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