Good cooking doesn’t just make food tasty
To a first approximation, every atom has just two parts – a central nucleus (from the Latin word for “nut”) and a cloud of electrons (from the Greek word for “amber,” which, when rubbed, provided the ancients with static electricity). The nucleus and electrons are both electrically charged – the nucleus is positive; electrons, negative.
Atoms “like” to have certain numbers of electrons in the outer portions of their clouds. To attain such a “magic number,” an atom will either take electrons from another, or give away some of its own.
Sharing electrons creates a chemical bond between atoms. Together, the bonded atoms form a molecule.
Some atoms hold on to shared electrons more tightly than others. Since the electrons are negative, atoms that hold them tightly develop something of a negative charge.
Atoms that hold the shared electrons more loosely develop something of a positive charge instead.
Opposites attract – positive to negative, negative to positive. The negative part of one molecule attracts the positive part of another. Our bodies – and the bodies of all other living things – take advantage of this attraction.
Our bodies build and repair themselves with molecular machines called enzymes. Lacking hands and fingers, enzymes make, break and haul around other molecules by electrical attraction. To be able to mate with the molecule it’s to work on, an enzyme must be positive or negative in just the right places, so the two will match. Not only must the electrical charges match up, the enzyme must be just the right shape.
Without enzymes of the right shape and charge distribution, we die.
Our bodies use proteins – long, stringy molecules that fold up like organic origami – to make enzymes of the proper shape. All along the protein molecule are regions of positive and negative charge. By attracting each other, these regions hold the protein – the enzyme – in the proper shape.
The white of an egg is composed of globular proteins that have folded into the shape of a ball of yarn. Not only must the positive and negative regions of such a molecule be in just the right places, but, as they’re folding, parts of the molecule must be guided into place by other molecules – “molecular chaperones” – lest the wrong parts stick together.
When an object is warmed, its atoms and molecules vibrate faster (which is why things expand when they’re heated – as they vibrate faster, their atoms and molecules push away from each other more violently). Heat an object enough and its molecules will vibrate so fast they destroy themselves.
Heat an egg, and its proteins may vibrate so hard they can no longer hold together. Ripped apart, the globular protein unfolds. Lacking the gentle environment of Mama Bird’s belly, and no longer guided by molecular chaperones, positive and negative regions of the stringy protein bind willy-nilly, creating a randomly shaped protein.
A protein that’s lost its proper shape is said to be “denatured.” An egg whose proteins have been denatured by heat is “hard boiled.”
A study headed by Susanne Lindgren of California State University at Sacramento, noted that, because the U.S. Department of Agriculture inspects meat only for certain strains of bacteria, other, potentially harmful strains can and do slip by.
Like all other living organisms, bacteria can survive only if their proteins are of the right shape. As new regulations force inspectors to check more meat in less time, it becomes ever more important to remember that proper cooking denatures proteins … and thus kills germs.
Trained as a biologist, Alan Stahler is also an amateur astronomer. He teaches biology and geology at Bitney Springs Charter High School. His science programs can be heard at noon on alternate Tuesdays on KVMR-FM (89.5).
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