Molecular Messages: The Language of Life Within Us

Genes don’t actually do anything by themselves: they are simply recipes that cells use to make proteins. The cells put away the recipes they don’t need and take out the ones they do, meaning that each cell is able to make its own particular set of proteins.

The DNA molecules are heavily guarded within the nucleus, like a highly exclusive cookbook. When the cell is about to generate a protein, it first makes a copy of the gene using RNA, a molecule similar to DNA. The RNA molecule then moves out of the cell nucleus and into the cell’s protein factory.

About eighteen days after conception of human life, the cells form two small tubes, one on either side of the spine. Over the next few days, they move towards each other and merge. At the same time, the cells around the new tube change, taking on a very special role: they become heart-muscle cells. These cells spontaneously begin to contract, in and out, in and out. Always. No matter what.

All over your transparent body, tiny red specks appear; merging together to form your first blood vessels. Over the next few hours your cells must constantly build new blood vessels in order to reach out to all the nooks and crannies of your increasingly complex body. These vessels branch out into smaller and smaller byways, the smallest of which are called capillaries. These are so narrow that there is room for only a single, tiny blood cell to squeeze through them.

If you were to place ten capillaries side by side, they’d be about the width of a human hair.

Nearly all animals have roughly the same number of heartbeats during their lives. Small animals live shorter and have fast-beating hearts, while large animals live longer and have more slow-beating hearts. Humans are a clear exception to this, and live far longer than our seventy beats per minute would predict.

A mouse’s little heart beats fast and feverishly – at least 450 times per minute – for only a year or two, before giving up. At the opposite end of the spectrum we have the blue whale, the largest animal that has ever existed. A blue whale has blood vessels so wide that we could swim through them, and can live to be one hundred years old. Its heart, weighing more than lookg, beats under ten times a minute – each pulse sending a thousand litres of blood coursing through its gigantic body – and is so loud that it can be heard many kilometers away.

The language of cells is written in molecules. They communicate by sending and receiving chemical mes-sages, often different proteins. Some of them resemble loud cries, and race through blood from one end to another.

If you’ve just eaten, your pancreas screams out a protein: INSULIN! And once the liver cells receive this protein message, they begin to assemble blood sugar into long chains which they save for later. It would be terribly confusing and tiring for the liver if the pancreas didn’t keep it updated about your daily meals. Your liver takes care of your blood sugar and has to alter-lace between storing your energy for later and using it now.

All cells are surrounded by a thin film called the cell membrane, and only a few molecules manage to sneak through it into the cell without permission. Instead, most of the messages are delivered indirectly by hooking on to a type of molecule called a receptor, which sits on the cell’s surface. The messages fit the receptors like a key fits a keyhole. For example, on the surface of a liver cell there is a receptor for insulin. When the insulin molecule hooks on to the receptor, it triggers a chain reaction within the cell, and the liver cells begin to store nutrition.

Many diseases occur due to communication failure between cells. In type I diabetes, the pancreas struggles to be heard – it cannot produce enough insulin. For unknown reasons, the body’s immune system begins to attack the cells that make insulin, so that the usual Oi! to the liver comes out more like a polite Ahem. That means it’s up to the patient to supply insulin messages o the body using a syringe. In type I diabetes, the pancreas attempts to report that the person has eaten, but he cells don’t hear it. The insulin passes through the blood, but the receptors on the cell’s surface struggle to pick it up. The danger with diabetes is that the cells are convinced they are starving, no matter how heartily the person eats. The liver, oblivious, keeps breaking down its energy reserves and the blood sugar level becomes dangerously high. Unable to use the sugar, the body has to get rid of it through the urine.

Insulin is just one of many substances that the cells in your body use to communicate. By staying in touch with one another, they become a resilient, well-functioning community, one that contains more inhabitants than there are known galaxies in the universe.

Source : The Making of You: A Journey from Cell to Human by Katharina Vestre

Goodreads : https://www.goodreads.com/book/show/42121353-the-making-of-you

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