9781422280485

Chemistry and Classification

different sequences and chain lengths. (Think of it the way the 26 letters in our alphabet can create over a million words, each with its own meaning and usage.) After the amino acids link up, they fold and coil into three-dimensional shapes. The shape is crucial to the protein’s function, since it determines what other molecules it can interact with. Our bodies can manufacture 11 of the 20 protein-building amino acids on their own. These are known as nonessential amino acids , since we don’t need to get them from outside sources like food. Eight of those nonessential amino acids are called conditional , meaning that our body can produce them but may not make enough if we are sick or stressed out. The remaining 9 of the 20 amino acids are called essential amino acids; our bodies can’t produce these, so we need a steady supply of them from our diets. P rotein C lassification : S ource and S hape With all the different types of proteins to keep track of, scientists need to have ways of classifying them. The most basic classification is between animal and vegetable proteins. Animal proteins come from animal sources, like meat, fish, or dairy products. Vegetable proteins come from plants. Both animal and vegetable proteins are made of the same 20 amino acids. The difference is that plants do not consume other living things to get their amino acids, so they must manufacture all 20 on their own. Because animal-based proteins are similar to those already found in our bodies, we can use them more efficiently than plant-based proteins. They also contain a complete balance of all nine essential amino acids. Plant-based protein sources have lower amounts of some of these amino acids. This doesn’t mean they aren’t good for us; it just means we need to eat a wide variety of vegetables, nuts, legumes, and other plant-based foods to get all the amino acids we need if we are not eating meat.

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