Cholesterol is an important biomolecule that your cells need in order to maintain regular function. You can obtain cholesterol from your food, or synthesize -- meaning produce -- it from certain components of the food you eat. Cholesterol metabolism refers to the sum of all chemical reactions that produce cholesterol or use cholesterol to produce other biomolecules; a wide variety of metabolic reactions involve cholesterol in some regard.
Identification
The cholesterol molecule generally has a bad reputation where human health and well-being are concerned. For instance, you may know that having high blood cholesterol puts you at risk for heart disease. Furthermore, you've probably heard that foods high in cholesterol and fat aren't healthy and can raise your blood cholesterol levels. In fact, however, you need a certain amount of cholesterol. It helps regulate the integrity of cell membranes, and you use it to make hormones and vitamins.
Making Cholesterol
While you can get cholesterol directly from your food, you can also make it. Cholesterol synthesis is the chemical name for a series of reactions that produce cholesterol from acetyl-CoA, which is a breakdown product of nutrient molecules. You make acetyl-CoA any time your cells burn carbohydrate, fat or protein for energy. Acetyl-CoA does many different things; making cholesterol is only one of them.
Synthesis Pathway
The pathway by which you make cholesterol from acetyl-CoA is quite long and complicated and involves many different enzymes. Enzymes are proteins that help chemical reactions take place faster than they otherwise would. The reason enzymes are so important to cholesterol synthesis is that the cells can regulate the enzymes -- turn them on or off -- such that under normal circumstances you only produce cholesterol when your cells need it.
Other Metabolic Reactions
Many other metabolic reactions involve cholesterol as a starting material. Cholesterol is the material your cells use to produce vitamin D, which helps you absorb calcium from the food you eat. Cholesterol in your skin reacts with sunlight, converting it into the vitamin. You also make many different hormones -- a hormone is a chemical signaler that helps cells communicate with one another -- from cholesterol. Examples include testosterone, estrogen and progesterone.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
