The picture above is of an Alanine molecule. Alanine is one of 20 or so amino acids found in living things, and that make living things possible. There is only one amino acid that's simpler than Alanine. The others are more complex. The graphic is modified, with permission, from one found on en.wikipedia.org. The spheres represent atoms. The rods, some very thick, represent bonds between the atoms.
Life on earth is often called Carbon-based, and there's good reason for that. The reason is that Carbon is the basis of the complex molecules that make up living things, including DNA, proteins, antibodies, sugars, fats, steroids, vitamins, hormones, proteins, caffeine, the alkaloids found in chocolate, and many more.
Suppose you were in a group of people, and that group decided that each person would hold hands with two other people. If you did, the most complex arrangement you could make is a line, perhaps not a straight line, but a line. The line might be a loop, but it would still be a line. Now suppose that you and the others could hold on with hands, and also with feet. The possibilities for arrangements are much greater with four connections per person. Well, Carbon is like that, too. It readily forms four connections, called covalent bonds, with other atoms. Usually these are Hydrogen, Nitrogen, Oxygen, Sulfur or Phosphorus, or another Carbon atom. These six elements make up almost all of the molecules necessary for life.
The Alanine molecule shown above illustrates the ability of Carbon to connect to four different things. Alanine has a central Carbon. That Carbon is attached to 4 different entities. One of them is a Hydrogen molecule. The other three are more complex. Two of them, the COOH and the NH2, are found in all other amino acids. But the CH3 group, a methyl, is not. The other amino acids have some other entity in its place. Each of the amino acids found in us has a different item connected to the central Carbon. All 20 of these amino acids are necessary to make hemoglobin, the molecule that carries Oxygen around your body in the bloodstream. Hemoglobin is much more complex than Alanine -- it has 147 amino acids, of 20 different types, including 11 Alanines. Those 147 amino acids have to be of the right kind, at the right place, in order for Hemoglobin to work properly.
The ability to connect to four other things is critical to the complex structure of the molecules of living things. Can any other type of atom do that? Well, Silicon can. It's a member of the same family of elements as Carbon. But Carbon works for us in a way that Silicon can't. Carbon is a smaller atom -- a Carbon atom has less than half the mass of Silicon. Silicon is too heavy to float into the air. But Carbon, with other atoms, forms gases, which can get into the air. One of these is Carbon Dioxide. Carbon Dioxide can go anywhere on earth, as a gas, through the air. Photosynthesis, the process that makes our food, takes in Carbon Dioxide and water, and turns it into food. The green plants that carry out photosynthesis can grow in a wide variety of situations, because they can make their own food in them. And the animals that live on green plant food can also exist in a wide variety of locations, all throughout the biosphere. If our molecules were based on Silicon, that wouldn't be possible.
I believe that God planned the universe, including the properties of Carbon atoms. I can't prove this, but no one can disprove it, either, even those who say that those properties are an accident.
I'm thankful for Carbon atoms, and the amazing things that they are able to do, connected to other atoms. I hope you are, too. Thanks for reading.
A later post indicates the reasons why I'm thankful for water.
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