Compounds From the 92 elements that exist, more than three million different compounds have been formed Compounds are formed when two or more different kinds of elements combine chemically in fixed amounts Almost 95 percent of these compounds are organic. This means that the compounds contain the element carbon The majority of compounds found in cells are organic. Water and edrochlonic acid are two exceptions. Most organic compounds in living systems can be put into one of four": (1) carbohy. dates sugars, starches, and cellulose: (2) lipids: fats, oils, and waxes: 3) proteins; and (4) nucleic acids. You can see examples of some of Carbohydrates these organic compounds to the right and below. Fats Proteins Nucleic acids
染色体的结构 (一)染色体的化学组成 DNA (1) 染色体{ PROTEIN(15~2.5)组蛋白(1) RNA(005) 非组蛋白0.5~1.5
二、染色体的结构 （一）染色体的化学组成 DNA （1） 染色体 PROTEIN(1.5~2.5) 组蛋白(1) RNA(0.05) 非组蛋白(0.5~1.5)