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注册: 2012-02-21
专业: 生物大分子结构与功能

[求助] 生物化学-求助几个关于RNA,LIPID,糖类问题

. Nucleic Acids:
问题比较多，，求大神详解。。有一些我在课件里找不到，有一些我对问题想问的点比较迷惑。。自己答得不准没分，谢谢谢谢！！！！大家可以轮流答一些问题。。我真的很需要帮助。。T-T
1. What are the three ways that the heterocyclic bases stabilize double helices in noncoding RNA.
2.Explain how the tertiary structure of an RNA molecule is determined by its nucleotide sequence.
3. It is important for translation purposes that mRNA does not fold into a stable structure. What is the main characteristic of the mRNA primary structure that ensures that the mRNA will not fold into a stable secondary/tertiary structure.
4. Describe the hierarchy of RNA folding and identify the major forms of stabilization of the secondary and tertiary structure.

5. Explain the restrictions that the RNA phosphate diester groups place on secondary and tertiary RNA structure.
6. There is less diversity of tertiary structure of noncoding RNA than there is for proteins-why is this the case?
7.    What is believed to have evolved first: proteins or RNA?
8. Why do you think is the central reason why proteins have out-competed RNA for most of the functional jobs in the cell (chemical catalysis and beyond).
9. Explain why DNA exists in the cell as heterodimer whereas RNA exists as a monomer.
10. Draw a cartoon of the DNA double helix and point out where the sugar phosphodiester backbone is located and where the heterocyclic rings (“bases”) are located.
11. The two DNA molecules that make up the DNA double helix have complementary sequences. Illustrate and explain what is meant by “complementary sequences”.
12. Describe the role that the low polarity which exists in the core of the DNA double helix plays in stabilizing the helix.
13. In associating to form a double helix the two DNA molecules lose entropy. Illustrate and explain the sources of this entropy loss.
14. The association of two DNA molecules to form a double helix results in the increase of the water solvent entropy. Explain why.
15. The phosphate groups of the DNA do not contribute to the stability of the double helix. Explain why.
16. List the three ways that the heterocyclic rings (“bases”) contribute to the stability of the DNA double helix. H-bonding base ,, dopole dipole and ,,, desolvation
17. List the two differences in the covalent structure of DNA and RNA.
18. Illustrate and explain how the deoxyribose  makes DNA less susceptible to fragmentation by hydrolysis than RNA
Relatively low entropy loss in transition state.
Delta S contribute to delta G in TS.
19. Illustrate and explain how the thymidine instead of uridine makes DNA less susceptible to damage by Uv light than RNA

[ Last edited by 1949stone on 2012-10-29 at 07:24 ]

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