The lesson started with a discussion about the chemical level of organization in living organisms.The division into inorganic and organic compounds was outlined, with examples of each. The organic compounds are carbohydrates, nucleic acids, lipids, and proteins. These were shown to constitute hormones, enzymes, neurotransmitters, and brain chemicals. Acetylcholine, norepinephrin, serotonin, dopamine and GABA. A discussion around the importance of these neuro chemicals, specific types of hormones, and digestive enzymes was presented. The chemical structure of these will be discussed individually, and compared to some exogenous drugs.