Among the most important classes of biomolecules are nucleic acids, proteins, carbohydrates, and lipids. 1) Nucleic acids are responsible for storing and transferring genetic information. They are enormous molecules made up of long strands of subunits, called bases, that are arranged in a precise sequence. These are "read" by other components of the cell and used as a guide in making proteins. 2) Proteins are large molecules built up of small subunits called amino acids. The proteins of greatest interest to biochemists are the enzymes, which serve as catalysts, of chemical reactions. 3) Carbohydrates are the basic fuel molecules of the cell. they contain carbon, hydrogen, and oxygen in approximately equal amounts. Green plants and some bacteria use a process known as photosynthesis to make simple carbohydrates (sugars) from carbon dioxide, water, and sunlight. Animals, however, obtain their carbohydrates from foods. Once a cell possesses carbohydrates, it may break them down to yield chemical energy or use them as raw material to produce other biomolecules. 4) Lipids are fatty substances that play a variety of roles in the cell. Some are held in storage for use as high-energy fuel; others serve as essential components of the cell membrane.
- class [klɑ:s] n.类
- biomolecule [ˌbaiəuˈmɔlikju:l] n.生物分子
- nucleic acid [nju:ˈkli:ik - ˈæsid] n.核酸
- protein [ˈprəuti:n] n.蛋白质
- carbohydrate [ˌkɑ:bəuˈhaidreit] n.碳水化合物
- lipid [ˈlipid,ˈlaipid] n.脂质,油脂
- be responsible for [bi: - riˈspɔnsəbl - fɔ:] n.为…负责
- enormous [iˈnɔ:məs] adj.巨大的, 庞大的
- strand [strænd] n.线、束、串
- subunit [sʌbˈju:nit] n.子[分,亚]组
- base [beis] n.碱基：嘌呤(腺嘌呤和鸟嘌呤)或嘧啶(胸嘧啶、胸腺嘧啶和尿嘧啶)的一种
- precise [priˈsais] adj.精确的
- sequence [ˈsi:kwəns] n.顺序，序列
- amino acid [ˈæminəu - ˈæsid] n.氨基酸
- biochemist [ˈbaɪəuˈkemɪst] n.生物化学家
- enzyme [ˈenzaim] n.酶
- catalyst [ˈkætəlist] n.催化剂
- chemical reaction [ˈkemikəl - ri:ˈækʃən] n.化学反应
- fuel [fjuəl] n.燃料, 能量
- carbon [ˈkɑ:bən] n.碳
- hydrogen [ˈhaidrədʒən] n.氢
- oxygen [ˈɔksidʒən] n.氧
- approximately [əprɔksiˈmətli] adv.大约
- carbon dioxide [ˈkɑ:bən - daiˈɔksaid] n.二氧化碳
- obtain [əbˈtein] v.获取
- cell membrane [sel - ˈmembrein] n.细胞膜
- yield [ji:ld] v.产出，生出
- fatty [ˈfæti] adj.含脂肪的，脂肪状的
- a variety of [ə: - vəˈraiəti -əv] adj.多种多样的
- break down [breik - daun] v.分解
