Lecture 4 – Symmetry, sensation and sex

From the 1992 lecture brochure:

Some of the molecules that are significant in our lives and for our life styles, like water, alcohol and natural gas, are not handed. In this lecture we look at the significance of a collection of small, handed molecules. We see, or rather taste, by experimenting on ourselves, that the signals from our noses and tastebuds respond to the chirality - handedness - of the molecules that reach them. This tells us that our sensory mechanisms are handed. Our emotions, such as fear, trigger the hormone adrenalin, a small handed molecule which makes it possible to stand and fight or run. It must have the correct handedness, this aspect can be crucial in medicine; different handed versions of a drug may have alarmingly different effects. Sex depends directly on molecular handedness. Testosterone in the human male controls sexual activity and produces, amongst other things, a beard and a deep voice; in canaries it can make the silent female sing. Oestrone controls sexual activity in females - an obvious requirement for the survival of the species.

Lastly, we look again at the sugars seen first in Lecture 2. We put vitamin C in its historical background and look at glucose, the marvellously versatile four-handed molecule. This is our energy carrier and the building block of the giant molecules cellulose, starch and glycogen without which most of nature as we know it would not exist. We come to these in Lecture 5.


Natural world


BBC / Royal Institution




Charles Stirling



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