TAILIEUCHUNG - Biochemistry, 4th Edition P115

Biochemistry, 4th Edition P115. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | Abbreviated Answers to Problems A-43 cally with phosphate groups on the DNA backbone so these interactions would be diminished through acetylation and methylation. Phosphorylation of Ser residues would lead to electrostatic repulsion between the DNA backbone and the histone tails. Collectively these modifications weaken histone DNA interactions. 10. Because the lac repressor is tetrameric and each subunit has an inducer-binding site it seems likely that inducer binding is cooperative. Cooperative binding of inducer would be advantageous because the slope of the lac operon expression versus inducer would be steeper over a narrower inducer range. 11. Capping of the 5 -end and polyadenylation of the 3 -end of mRNA protect the RNA from both 5 - and 3 -exonucleolytic degradation. Methylations at the 5 -end enhance the interaction between cap-binding protein eIF4E see Figure thus increasing the likelihood that the mRNA will be translated. Note also in Figure that polyadenylylation provides a proteinbinding site for proper assembly of the 40S initiation complex essential to translation. 12. In the A Deeper Look box on page 870 the argument is made that polymerases have a common enzymatic mechanism for nucleotide addition to a growing polynucleotide chain based on two metal ions coordinated to the incoming nucleotide. These metal ions interact with two aspartate residues that are highly conserved in both DNA and RNA polymerases. The discovery of a second Mg2 ion in the RNA polymerase II active site confirms to the universality of this model. 13. 50 bp of DNA is 50 nm bp 17 nm. Because 147 bp of DNA make turns around the nucleosome see Chapter 11 bp turn of DNA 50 bp turns or slightly more than turn of DNA around the histone core octamer. Promoter and response modules are about 20 to 25 bp. 14. O O P O O CH. NH. O P O o_ O O OH O CH P O CH O O P O O P O O OH O CH o O O P O nh2 O OH _O O 15. n-Helices composed of 7 to 8 residues would have a .

• Sinh học
• Nền tảng của hóa sinh học
• trao đổi chất protein
• RNA trao đổi chất
• nguyên tắc của hóa sinh
• Axit amin
• công nghệ DNA