Classes of Biochemical Compounds
Biochemical compounds make up the cells and tissues of living things. They are also involved in all life processes. Given their diversity of functions, it’s not surprising that there are millions of different biochemical compounds. Even so, all biochemical compounds can be grouped into just four main classes: carbohydrates, proteins, lipids, and nucleic acids. |
Carbohydrates
Carbohydrates are biochemical compounds that include sugar, starch, glycogen, and cellulose. Sugars are simple carbohydrates with relatively small molecules. Glucose is the smallest of all the sugar molecules with its chemical formula of C6H12O6. This means that a molecule of glucose contains 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen. Plants and some other organisms make glucose in the process of photosynthesis. Living things that cannot make glucose can obtain it by consuming plants or organisms that consume plants. Starches are complex carbohydrates. They are polymers of glucose. Starches contain hundreds of glucose monomers. Plants make starches to store extra glucose. Consumers can get starches by eating plants. Our digestive system breaks down starches to sugar, which our cells use for energy. Like other animals, we store any extra glucose as the complex carbohydrate called glycogen. Glycogen is also a polymer of glucose. |
Biochemical Reactions
The student athlete, shown to the right, is practically flying down the track! Running takes a lot of energy. But you don’t have to run a race to use energy. All living things need energy all the time just to stay alive. The energy is produced in chemical reactions. A chemical reaction is a process in which some substances, called reactants, change chemically into different substances, called products. Reactants and products may be elements or compounds. Chemical reactions that take place inside living things are called biochemical reactions. Living things depend on biochemical reactions for more than just energy. Every function and structure of a living organism depends on thousands of biochemical reactions taking place in each cell. |
Photosynthesis and Cellular Respiration
Some of the most important biochemical reactions are the reactions involved in photosynthesis and cellular respiration.
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