基因的分子生物学英文版答案molecular chapter3.pdfVIP

Chapter 3 Answers 1. Because secondary bonds are significantly weaker than covalent bonds, you could distinguish between these possibilities by assessing the overall stability of the protein or protein complex. Heating the enzyme, for example, would likely be sufficient to separate distinct polypeptide chains, but would not be enough to break apart a single chain. 2. Because covalent bonds are stronger, the length of the bonds is much shorter than it is with weak bonds. Also, covalent bonds are more constrained than weak bonds in several respects. For example, covalent bonds involving a double or triple bond have no freedom of rotation, in contrast with weak bonds, which are not limited by their relative orientation. In addition, the angle between any two covalent bonds is fixed, in contrast to the angle between any two weak bonds. Finally, a given atom can only bond with a very small number of other atoms (determined by its valence), whereas a weak bond has more flexibility in this regard. Because secondary bonds are generally too weak to support a stable interaction between molecules by themselves, stability must come from a collection of multiple wea bonds acting together. The flexibility of weak bonds can help in this regard, because it facilitates the formation of these multiple weak interactions. For example, when two proteins bind to each other, numerous secondary bonds are formed between the exposed molecular groups of each of the proteins. If each of these bonds were subject to the same rigid constraints of covalent bonds, the number of possible weak interactions would be limited, and the demands placed on the precise structure of each protein would be that much greater. 3. Beyond the obvious importance of strong (covalent) bonds in maintaining the primary structure of polymerase, other enzymes involved in DNA replication, and the DNA strands themselves, strong bonds are also important for providing the