生物化学(合工大)第一章 绪论(精品·公开课件).ppt

Formation of a hydrogen bond between the hydrogen side of one water molecule and the oxygen side of another water molecule. The presence of polar areas in the amino acids that makeup a protein allows for hydrogen bonds to form, giving the molecule a three-dimensional shape that is often vital to that proteins proper functioning. Electrostatic interactions Electrostatic interactions occur between oppositely charged atoms or groups. An important aspect of all electrostatic interactions in aqueous solution is the hydration of ions. Because water molecules are polar, they are attracted to charged ions. As ions become hydrated, the attractive force between them is reduced, and the charged species dissolves in the water. Dissolution of an ionically bonded compound, sodium chloride, by water molecules. van der Waals forces van der Waals forces are relatively week, transient electrostatic interactions. They occur between permanent and / or induced dipoles. They may be attractive or repulsive, depending on the the distance between the atoms or groups involved. There are three types of van der Waals forces: Dipole – dipole interactions Dipole – induced dipole interactions Induced dipoles – induced dipoles interactions. The mean van der Waals diameter of water is identical with that of isoelectronic neon (2.82 ?). Hydrophobic interactionsAs soon as nonpolar substances are mixed with water, they coalesce into droplets because water-water interactions are stronger than water-nonpolar substance interactions. This process results from hydrophobic interactions. 小 结 2、生物化学反应的基本规律 ① 生命活动过程是由数千化学反应组成的，相关联的化学反应形成代谢途径，不同的代谢途径连接形成代谢网络。 Chemical reactions Metabolic pathways Metabolic networks A?B, B?C, C?D, C?E, E?F A?B?C?D C?E?F A?B?C?D ? E?F 2、生物化学反应的基本规律 ② 生物化学反应是由酶催化的，反应的基本原理是相同的。 氧化还原反应 亲核反应 异构化反应 水解反应 合成反应 etc 反应很多，但反应的机制是相对较少的 2、生物化学反应的基本规律 ③ 生物化学反应实现了生命必须的物质转换、能量传递和信息交流的统一。 物质转换?生化反应的表现形式?生命平台 能量传递?生化反应的催化动力?生命活力 信息交流?生化反应的