An experiment uses healthy thyroid cells. TSH is added, and the cells release more thyroxine. A student says this proves that negative feedback occurs.
Why is this conclusion not supported by this experiment alone?
It does not test whether TSH increases thyroxine release.
It does not test whether thyroid cells respond to TSH.
It does not test whether thyroxine reduces TSH production.
It does not test whether thyroxine comes from thyroid cells.
42 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.