Chemical diversity at Higher Level: An AHL statement: the different kinds of molecule used as signals.
Practise this as you read
- Outline the chemical groups, with examples.
- Identify the group a named signal belongs to.
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The big idea: Hormones and neurotransmitters are chemically diverse. Hormones include amines (adrenaline), peptides and proteins (insulin) and steroids (testosterone). Neurotransmitters include amino acids (glutamate), amines (dopamine), acetylcholine and even a gas, nitric oxide.
The points to remember
- Amines: adrenaline, thyroxine; dopamine, serotonin.
- Peptides and proteins: insulin, glucagon, ADH; endorphins.
- Steroids: testosterone, oestradiol, cortisol (lipid-soluble).
- Amino acids: glutamate, glycine, GABA.
- Also acetylcholine and the gas nitric oxide.
Remember it as: Amines, proteins, steroids, and more.
Real example: a gas as a signal. Nitric oxide is a gas made by cells. It diffuses straight through membranes, acts as a neurotransmitter, and relaxes the smooth muscle in blood vessel walls so they widen.
Trap: Not every hormone is a protein: steroids are lipids, and adrenaline is a small amine.
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How it is asked: Expect an MCQ asking which signal belongs to a chemical group, or an Outline question asking for examples of each group.
IB-style questionOutline[3 marks]
Outline the chemical diversity of hormones, giving an example of each type.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.