Structural View of Biology
Enzymes are Nature's chemists, performing all of the chemical transformations needed for life. Enzymes catalyze chemical reactions by bringing together all of the necessary chemical tools in the proper place. They typically have an "active site" that captures the chemicals that will be modified, holding them in the perfect orientation to perform the chemical change. Researchers have separated the many types of enzymes into a few functional classes, based on the reactions that they perform. Click on any of the sub-categories below to explore a few examples of each enzyme class. You can also explore many other enzymes in the other functional categories in "Structural View of Biology."
Isomerases - Changing Molecular Shape
Isomerases shuffle atoms around in a molecule, changing its shape. This may be as simple as reversing the handedness of an amino acid, or as complicated as changing the topology of a DNA strand.
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Cholesterol has gained a bad reputation in recent years. It is absolutely essential in our lives: it is needed to keep our membranes fluid and it is the raw material used to build a host of important molecules such as vitamin D and steroid hormones. However, elevated levels of cholesterol (for instance from a fat-rich diet) have been linked to the formation of atherosclerosis and heart disease. Today, doctors suggest that a combination of a healthy low-fat diet and exercise will keep these two faces of cholesterol in balance.
Each of your cells contains about 2 meters of DNA, all folded into the tiny space inside the nucleus, which is a million times smaller. As you might imagine, these long, thin strands can get tangled very easily in the busy environment of the nucleus. To make things even more complicated, DNA is a double helix, which must be unwound to access the genetic information. If you have ever tried to unravel the individual fibers in a piece of rope, you will understand the knotty problems that this can cause. To help with these problems, your cells build several different topoisomerase enzymes that untangle and relax DNA strands.
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