Cells in the human body require many compounds to survive. The main substances found in every cell are a combination of lipids, carbohydrates, nucleic acids and proteins. Each of these substances plays a different role in the body, and all of them must either come from the diet or be manufactured using other chemicals in the body.
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Lipid Function in the Body
Lipids, also known as fats, play multiple roles in the body. Fats are broken down in the digestive tract to form individual fatty acids and cholesterol molecules. Fatty acids and cholesterol are key components of the membranes that surround all cells. Cholesterol can also be used to make many other compounds in the body, such as steroid hormones. Finally, fatty acids represent an important source of energy, particularly for the purposes of long-term storage.
Carbohydrates as Energy
Carbohydrates are the preferred source of energy for most of the tissues in the body, including the nervous system and the heart. Carbohydrates from the diet are converted into glucose, which can either be immediately used as a source of energy or stored in the form of glycogen. The body cannot digest all carbohydrates in the diet, however; indigestible carbohydrates, also known as fiber, travel through the intestines and can help maintain proper digestive health.
Nucleic Acids for Storing Information
Nucleic acids consist of three different types of molecules joined together: a sugar, a phosphate molecule and another molecule that contains nitrogen, called a nitrogenous base. The main role of nucleic acids is to store information that is used to make proteins. Nucleic acids come in two main forms: deoxyribonucleic acids, also known as DNA, and ribonucleic acids, also known as RNA. The main function of DNA is to store the genetic information that cells in the body need to function. RNA, on the other hand, plays an important role in converting the information from DNA into proteins.
Proteins as Workhorses of the Body
Proteins are large and fairly complex molecules that are responsible for doing most of the work that occurs in cells. They also are needed to maintain the structure of cells and are critical for the function and regulation of all of the body's tissues. The body uses the information stored in DNA to create proteins, which are made up of subunits called amino acids. Enzymes, which help speed chemical reactions in cells, are a specialized type of protein. Protein also plays a crucial role in maintaining muscle tissue, since muscle tissue has large amounts of protein. For muscles to increase in size and strength, more protein must be made to expand the muscle fibers.