chapter 4 enzyme

酶催化机理的研究Chapter 1 概述酶（enzyme），是生物体内最常见的催化剂。

酶可以提高反应速率，使其他反应物质更容易互相作用。

酶催化机理的研究是生物学、化学、生物化学和分子生物学等领域的重点研究方向。

在传统的机械模型中，酶被认为是一种钥匙-锁（lock-and-key）模型。

这一模型认为，反应物与酶结合时，酶与反应物的结构互补，因此有利于催化反应。

然而，由于酶催化非常规反应和识别区非常灵活，这种简单的模型难以解释酶的催化机理。

Chapter 2 酶催化的种类酶催化分为多种类型，其中最常见的是羟基化和脱羧反应。

在这些反应中，酶作为催化剂，通过特定的化学反应来加速反应速率。

除此之外，酶还可以催化水解和氧化反应。

水解反应是将底物分解成更小的分子的过程，氧化反应则涉及到与氧发生反应，产生水和二氧化碳等物质。

Chapter 3 酶催化机理酶催化机理的本质是催化剂与底物之间的相互作用。

酶可以通过多种途径来促进底物的化学反应，包括：（1）使得底物在活性中心附近聚集，从而形成化学反应所需的分子结构，从而提高反应效率；（2）通过调整底物分子的构象，从而使其更容易与其他分子发生反应；（3）通过与底物分子发生化学式作用，从而对底物分子进行催化转化。

目前，对于酶催化机理的研究主要集中在羟基化反应和脱羧反应等可逆催化反应中。

这些研究表明，酶在反应中发挥了非常重要的作用，不能简单地用传统的化学反应模型来解释。

Chapter 4 酶催化机理的研究方法酶催化机理的研究是非常困难的，因为酶的分子结构非常复杂，而且酶在单个分子水平上运动。

因此，研究酶催化机理需要一系列高精度的实验方法，如：（1）利用紫外-可见光谱（UV-Vis）和核磁共振（NMR）等技术，研究酶的分子结构和构象。

（2）利用X射线晶体学（X-ray）技术，测量酶分子的三维结构。

（3）利用分子动力学（MD）模拟等计算方法，研究酶的运动机制和反应过程中的分子结构变化。

生化历来都不画重点的，但留学生老是过不了，于是就有了这个重点资料，和我们考的差不多，但是英语的，求高人翻译啊Brief Exercises of BiochemistryChapter 1 The structure and function of proteinExplain the following terms1. peptide bond2. Amino acid residues3. Primary structure of protein4. isoelectric point5. Secondary structure of protein6. Tertiary structure of protein7. Domain8. Protein denaturation9. Quaternary structure of proteinAnswer the following questions briefly1. What is physiological significance of hemoglobin oxygen dissociation curve as S-shaped?2. Please describe physiological functions of proteins.Discuss the following questions (Essay questions)1. Explain the relationship between the primary and spatial structure and the function of protein.Chapter 2 The structure and function of nucleic acidsExplain the following terms1. primary structure of nucleic acids2. DNA denaturation3. Tm4. DNA renaturation5. nucleic acid hybridizationAnswer the following questions briefly1. What is the structural characteristics of an eukaryocyte mature mRNA?2. What is the biological significance of Tm?Discuss the following questions (Essay questions)1. Please compare the two types of nucleic acids (DNA and RNA) in the chemical composition, molecular structure, cell distribution and biological functions.2. Please describe the structural characteristics of the B-DNA.3. Describe the molecular composition, structural features and functions of tRNA.Chapter 3 EnzymeExplain the following terms1. enzyme2. enzyme active center3. enzyme competitive inhibition4. Km5. isoenzyme6. zymogen activationAnswer the following questions briefly1. Explains with examples the competitive inhibition characteristic and the practical significance.2. What is the relationship between the enzyme cofactor and vitamine?3. What is the physiological significance of zymogen?4. What is isoenzyme? What is clinical significance of isoenzyme?5. How many kinds of essential group of enzyme are there? What is the role of each?Chapter 4 Metabolism of carbohydrateExplain the following terms1. glycolysis2. glycolytic pathway3. tricarboxylic acid cycle4. gluconeogenesis5. blood sugarAnswer the following questions briefly1. Describe briefly source and fate of blood sugar2. Describe briefly the physiological significance of gluconeogenesis3. Describe briefly the physiological significance of glycolysis4. Describe briefly the outline of TCA cycle5. Describe briefly the physiological significance of TCA cycle6. Describe briefly the physiological significance of pentose phosphate pathway7. Outline the reasons for the formation of lactic acid cycle and the physiological significance.8. Overview the important role of B vitamins in glucose metabolism.9. Why 6-phosphate glucose dehydrogenase activity will increase after uptake high-carbohydrate diet?Discuss the following questions (Essay questions)1. Explain how is lactate converted into glucose? (Write down the main reactions and key enzymes)2. Explain how is lactate converted into CO2, H2O and releases ATP? (Write down the main reactions and key enzymes)3. Overview the regulation molecular mechanism of adrenaline on the blood sugar level.4. Please explain why a slimmer has to reduce the intake of carbohydrates from the point of view of nutrients metabolism. (Write down the related pathways, cellular localization, main reactions and key enzyme)Chapter 5 Metabolism of lipidsExplain the following terms1. fat mobilization2. ketone body3. plasma lipoprotein4. apolipoprotein5. essential fatty acid6. blood lipidsAnswer the following questions briefly1. What is the function of bile acid at lipids digestion?2. What is the physiological significance of ketone body generation?3. What are materials of fatty acid synthesis?4. What is the physiological significance of cholesterol?5. What are the functions of apolipoprotein?Discuss the following questions (Essay questions)1. Describe the sources, chemical composition characteristics and main physiological functions of plasma lipoprotein.2. Explain how is the stearic acid converted into CO2, H2O and releases ATP?3. Please describe the oxidation catabolism process of glycerol generated from fat mobilization4. Explain how is the glycerol converted into glycogen?5. Describe the source and fate of acetyl-CoA?Chapter 6 Biological oxidationExplain the following terms1. biological oxidation2. respiratory chain3. oxidative phosphorylation4. substrate level phosphorylationDiscuss the following questions (Essay questions)1. Write down the sequence of two respiratory chainChapter 7 Metabolism of amino-acidExplain the following terms1. essential amino acid2. deamination of amino acid3. transamination of amino acid4. one carbon unit5. hyperammonemiaAnswer the following questions briefly1. What is the physiological significance of one carbon units?2. What is meaning of PAPS, GABA, SAM and FH4 each?3. Write down the deamination of amino acids in vivo.4. Outline the source and fate of blood ammonia.Discuss the following questions (Essay questions)1. How does a glutamate be oxidized to supply energy? What is the final product?2. What are functions of vitamins B in the metabolism of amino acids?3. Use the alanine as an example, try to explain the gluconeogenesis process of glucogenic amino acids.Chapter 8 Metabolism of nucleotideExplain the following terms1. de novo synthesis pathway of purine nucleotide2. nucleotide antimetaboliteAnswer the following questions briefly1. Outline the biological function of nucleotide.2. Outline the physiological significance of salvage synthesis of purine nucleotide.Discuss the following questions (Essay questions)1. Use the 6-mercaptopurine as an example, please explain the mechanism of antimetabolite.Chapter 10 Biosynthesis of DNAExplain the following terms1. semi-conservative replication2. reverse transcription3. replication4. excision repairing5. frame-shift mutationAnswer the following questions briefly1. Outline the classification and function of prokaryote DNA polymerase.2. Outline the classification and function of eukaryote DNA polymerase.3. Outline the factors causing DNA damage.4. Outline the repairing of DNA damage.5. Outline the central dogma.Discuss the following questions (Essay questions)1. Describe the materials involved in prokaryote DNA replication and their functions in that process.2. Describe the biological significance of mutation.Chapter 11 Biosynthesis of RNAExplain the following terms1. transcription2. posttranscriptional process3. hnRNA4. promoter5. ribozyme6. structure geneAnswer the following questions briefly1. Outline the eukaryote posttranscriptional process.2. Outline the products of three kinds of eukaryote RNA polymerases.Discuss the following questions (Essay questions)1. Describe the similarity and dissimilarity of replication and transcription.Chapter 12 Biosynthesis of proteinExplain the following terms1. translate2. polyribosomes3. genetic code4. degeneracy of codonAnswer the following questions briefly1. Describe briefly the RNAs involved in the protein synthesis and their functions in that process.2. Outline the main features of the genetic code.3. Describe briefly the dissimilarity of translation initiation complex formation of prokaryotes and eukaryotes.Discuss the following questions (Essay questions)1. Describe the materials involved in protein biosynthesis and their functions in that process.3. Please comparing the process of translation of prokaryotes and eukaryotes.Chapter 13 The regulation of gene expressionExplain the following terms1. gene expression2. cis-acting element3. trans-acting factor4. operon5. general transcription factor6. enhancerAnswer the following questions briefly1. What is biological significance of regulation of gene expression?2. Outline the function of each component of operon.3. What characteristics does eukaryotic genome structure have?Discuss the following questions (Essay questions)1. Explain the regulation mechanism of lactose operon.Chapter 14 Gene recombination and gene engineeringExplain the following terms1. restriction endonuclease2. genomic DNA3. vector4. cDNA. library5. genetic engineering6. DNA cloning7. homologous recombinationAnswer the following questions briefly1. What are the main selection criteria of gene vector?2. What is the significance of restriction endonuclease of bacteria themselves?3. At present, How many ways to get target genes?4. Outline the basic process of DNA cloning.Discuss the following questions (Essay questions)1. Why plasmid can be used as the vector of genetic engineering?2. Explain how to connect the foreign gene and the vector.3. What is α-complementary? Explain how to screening recombinant by it using an example.Chapter 15 Cellular signal transductionExplain the following terms1. signal transduction2. receptor3. ligand4. signal transduction pathway5. protein kinase6. second messenger7. G proteinAnswer the following questions briefly1. Describe briefly which protein kinases are regulated by intracellular second messenger.2. Outline the classification of receptor and its chemical signals.3. Describe briefly the basic mode of G protein-coupled receptor (seven transmembrane receptor)-mediated signal transduction.4. Describe briefly the signal transduction pathway of intracellular receptor of steroid hormone.Discuss the following questions (Essay questions)1. How does intracellular receptor play its function?2. Explain the process of the glycogen metabolism regulated by glucagon.3. Use fat mobilization as an example, explain the process of cAMP-protein kinase pathway. Chapter 16 Blood biochemistryExplain the following terms1. 2, 3-BPG shuntAnswer the following questions briefly1. Outline the function of plasma protein.Chapter 17 Liver biochemistrExplain the following terms1 biotransformation 2. primary bile acid 3. secondary bile acid4. bile pigment5. jaundiceAnswer the following questions briefly1. Describe briefly the physiological significance of biotransformation.2. Outline the main physiological functions of bile acids.3. Describe briefly production and blood transportation of bilirubin.Discuss the following questions (Essay questions)1. Describe the influence factor of biotransformation.2. Explain the dissimilarity of unconjugated and conjugated bilirubin.Chapter 18VitaminsExplain the following terms1. vitamin2. lipid-soluble vitamin3. water-soluble vitaminAnswer the following questions briefly1. Outline the biochemical function of vitamin E.2. Describe briefly the biochemical function of vitamin D and its deficiency disease.Discuss the following questions (Essay questions)1. Explain the relationship between the water-soluble vitamin and the coenzyme. Chapter 20 Oncogenes, tumor suppressor genes and growth factorExplain the following terms1. oncogene2. proto-oncogene3. tumor suppressor geneAnswer the following questions briefly1. Describe characteristics of proto-oncogene.2. Describe briefly wild-type p53 tumor suppressor gene mechanism.Chapter 21 The Principle and Application of Common Used Techniques in Molecular Biology Explain the following terms1. probe2. PCR3. Gene diagnosis4. gene therapyDiscuss the following questions (Essay questions)1. Describe the definition, type and application of the blotting technique.2. Describe the PCR reaction principle and the basic steps.。

第四章酶分子修饰与应用1 酶分子修饰(Modification of Enzyme Molecule)：通过各种方法使酶分子的结构发生某些改变，从而改变酶的某些特性和功能的过程。

2 酶分子修饰的意义？（1）提高酶的活力；（2）增强酶的稳定性；（3）降低或消除酶的抗原性；（4）研究和了解酶分子中主链、侧链、组成单位、金属离子和各种物理因素对酶分子空间构象的影响，进一步探讨酶分子的结构与功能之间的关系。

第一节酶分子的主链修饰1 酶分子的主链修饰：利用酶分子主链（肽链或核苷酸链）的切断和连接，使酶分子的化学结构及其空间结构发生某些改变，从而改变酶的特性和功能的方法。

2 酶分子主链修饰的意义？（1）可提高酶的活力；（2）可降低或消除酶的抗原性；（3）可预测酶活性中心在主链上的位置，从而了解主链的不同位置对酶的催化功能的贡献。

（一）主链的切断修饰①主链断裂后，引起酶活性中心的破坏，酶的催化功能丧失（用于探测酶活性中心的位置）。

②主链断裂后，酶活性中心的空间构象维持不变，酶的催化功能也可以保持不变或损失不多，但是抗原性有发生改变。

这样可以提高药用酶的使用价值。

③主链断裂有利于酶活性中心的形成，则可使酶分子显示其催化功能或使酶活力提高。

（二）主链的连接修饰将两种或者两种以上的酶通过主链连接在一起，形成一个酶分子具有两种或者多种催化活性的修饰方法称为酶的主链连接修饰。

在一个酶分子上具有两种或多种催化活性的酶称为多酶融合体。

通过基因融合技术将两种或两种以上的酶的基因融合在一起形成融合基因，再经过克隆和表达，有可能获得各种多酶融合体。

第二节酶的侧链基团修饰采用一定的方法使酶的侧链基团发生改变，从而改变酶分子的特性和功能的修饰方法称为侧链基团修饰。

酶的侧链基团的意义：（1）可以研究各种基团在酶分子中的作用，并可以用于研究酶的活性中心中的必需基团。

如果某基团修饰后不引起酶活力的显著变化，则可以认为此基团属于非必需基团；如果某基团修饰后使酶活力显著降低或丧失，则此基团很可能是酶催化的必需基团。

Chapter 2. CarbohydratePart I Definitions1.Polysaccharide2.Furanose3.Pyranose4.Chiral carbon5.Conformation6.Configuration7.Epimer8.Anomeric carbon atom9.Glycosidic bondPart II1. How does glycogen differ from starch in structure and function?2. Draw Howorth projection formulas for dimmers of glucose with the following types of glycosidic linkages:(1). Aβ(1→4) linkage (both molecules of glucose in theβform)(2). An α,α(1→1) linkage(3). A (1→6) linkage (both molecules of glucose in theβform)3. Glycogen is highly branched. What advantage, if any, does this provide an animal?4. No animal is able to digest cellulose. Try to explain this statement with the fact that many animals are herbivores that depend heavily on cellulose as a food source.Chapter 3. LipidPart I Definitions1 Essential fatty acids2 Unsatured fatty acids3 Phospholipid4 Fluid mosaic model5 Passive transport6 Active transportPart II1. What structural features do a triacylglycerol and a phosphatidyl ethanolamine have in common? How do the structures of these two types of lipids differ?2. A membrane consists of 50% protein by weight and 50% phosphoglycerides by weight. The average molecular weight of the lipids is 800 daltons, and the average molecular weight of the proteins is 50,000 daltons. Calculate the molar ratio of lipid to protein.3. Write the structure formula for a triacylglycerol, and name the component parts.4. Write an equation, with structural formulas, for the saponification of the triacylglycerol as above.5. Which of the following lipids are not found in animal membrane?(1) Phosphoglycerides (2) Glycolipid(3) Cholesterol (4) Sphingolipid(5) Triacylglycerols6. Which of the statements is (are) consistent with what is known about membrane?(1) A membrane consists of a layer of proteins sandwiched between tow layers of lipids.(2) The compositions of the inner and out lipid layers are the same in any individual membrane.(3) Membranes contain glycolipids and glycoproteins.(4) Lipid bilayers are an important component of membranes.(5) Covalent bonding takes place between lipids and proteins in most membranes.7. Which statements are consistent with the fluid mosaic model of membranes?(1) All membrane proteins and lipids are bound to the interior of the membrane.(2) Both proteins and lipids undergo transverse (“flip-flop”) diffusion from the inside to the outside of the membrane.(3) Some proteins and lipids undergo lateral diffusion along the inner or outer surface of the membrane.(4) Carbohydrates are covalently bonded to the outside of the membrane.(5) The term “mosaic refers to the arrangement of the lipid alone.”Chapter 3. Amino acid and proteinPart I1.Which amino acid is technically not an amino acid?Which amino acid contains no chiral carbon atoms? amino acid(s) in which the R group contains the following:a hydroxyl group:a sulfur atom:a second chiral carbon atom:an amino group:an amide group:an acid group:an aromatic ring:a branched side chain:3.Given a peptide with the following amino acid sequence:V al-Met-Ser-Ile-Phe-Arg-Cys-Tyr-LeuIdentify the polar amino acids, the aromatic amino acids, and the sulfur-containing amino acids.4.Are amino acids other than the usual 20 amino acids found in proteins? If so, how are suchamino acids incorporated into proteins? Give an example of such an amino acid and a protein in which it occurs.5.In the following peptide:Glu-Thr-V al-Asp-Ile-Ser-AlaIdentify the nonpolar amino acids and the acidic amino acids.6.Match the following statements about protein structure with the proper levels of organization.(a) Primary structure (1) The three-dimensional arrangement of all atoms(b) Secondary structure (2) The order of amino acid residues in the polypeptide chain(c) Tertiary structure (3) The interaction between subunits of proteins that consistsof more than one polypeptide chain(d) Quaternary structure (4) The hydrogen –bonded arrangement of the polypeptidebackbone7.Define denaturation in terms of the effects of secondary, tertiary, and quaternary structure.8. List five forces that are responsible for maintaining the correct three-dimensional shapes of protein. Specify which groups on the protein are involved in each type of interaction.9. The five principal types of bonds or forces that stabilizes protein structure are covalent bonds, ionic interactions, hydrogen bonds, metal complexation, and hydrophobic interactions. Which types stabilize primary, secondary, tertiary, and quaternary structure in protein?10. List two similarities and two differences between hemoglobin and myoglobin.11. List some of the differences between the α-helix and β-sheet forms of secondary structure.12. List some of the possible combinations ofα-helices and β-sheets in supersecondary structures.13. A sample of an unknown peptide was divided into two aliquots. One aliquot was treated with trypsin and the other with cyanogen bromide. Given the following sequences (N-terminal to C-terminal) of the resulting fragments, deduce the sequence of the original peptide.Trypsin treatmentAsn-Thr-Trp-Met-Ile-LysGly-Tyr-Met-Gln-PheV al-Leu-Gly-Met-Ser-ArgCyanogen bromide treatmentGln-PheIle-Lys-Gly-Tyr-MetSer-Arg-Asn-Thr-Trp-Met14. A sample of a peptide of unknown sequence was treated with trypsin; another sample of the same peptide was treated with chymotrypsin. The sequences (N-terminal to C-terminal) of the smaller peptides produced by trypsin digestion wereMet-V al-Ser-Thr-LysV al-Ile-Trp-Thr-Leu-Met-IleThe sequences of the smaller peptides produced by chymotrypsin digestion wereAsn-Glu-Ser-Arg-V al-Ile-TrpThr-Leu-Met-IleMet-V al-Ser-Thr-Lys-Leu-PheDeduce the sequence of the original peptide.Part II Definitions1 Isoelectric point2 Ninhydrin reaction3 Tertiary structure4 Motif5 Chaperone6 Chromatography7α-helix8 Protein denaturation9 Allosteric effect10 Bohr effect11 Molecular disease12 HbSChapter 4, 5. Enzyme, Vitamin and CoenzymePart I. Definitions1. Ribozyme2. Abzyme3. Coenzyme and Prosthetic group4. Isozyme5. Noncompetitive inhibition and Uncompetitive inhibition6. Allosteric enzyme7. ZymogenPart 2.1.Is the following statement correct? Explain your answer.Some enzyme-catalyzed reactions cease completely if their enzyme is absent.2. The curve described by the Michaelis-Menten equation:Rate (v) = Vmax [S]/([S] + Km)How can the equation be simplified when the substrate concentration is in one of the following ranges: (A) the substrate concentration [S] is much smaller than the Km, (B) the substrate concentration [S] equals the Km, and (C) the substrate concentration [S] is much larger than the Km?3. The rate of a simple enzyme reaction is given by the standard Michaelis-Menten equationv = Vmax[S]/([S] + Km)if the Vmax of an enzyme is 100 μmol/sec and the Km is 1 mM, at what substrate concentration is the rate 50 μmole/sec? Plot a graph of rate (v) versus substrate concentration (s) for [S] = 0 to 10 mM. Convert this to a plot of 1/rate (1/v) versus 1 [S]. Why is the latter plot a straight line?4. Select the correct options in the following and explain your choice.If [S] is much smaller than Km, the active site of the enzyme is mostly occupied/unoccupied.If [S] is very much greater than Km, the reaction rate is limited by the enzyme/substrate concentration.5. The reaction rates of the reaction S→P catalyzed by enzyme E were determined under conditions such that only very little product was formed. The following data were measured: Substrate Concentration (μM) Reaction Rate (μmole/min)0.08 0.150.12 0.210.54 0.71.23 1.11.82 1.32.72 1.54.94 1.710.00 1.8Plot the above data as a graph. Use this graph to find the Km and the Vmax for this enzyme. Assume the enzyme is regulated: upon phosphorylation, its Km increased by a factor of 3 without changing its Vmax. Is this an activation or inhibition?6. Which of the following statements are correct? Explain your answer.A.The active site of an enzyme usually occupies only a small fraction of its surface.B.Catalysis by some enzymes involves the formation of a covalent bond between an amino acidside chain and a substrate molecule.C.Allosteric enzymes have two or more binding sites.7. Simple enzyme reactions often conform to equationE + S ↔ES↔E + PWhere E, S, and P are enzyme, substrate, and product, respectively.A.What does ES represent in this equation?B.Why does E appear at both ends of the equation?pound X resembles S and binds to the active site of the enzyme but cannot undergo thereaction catalyzed by it. What effects would you expect the addition of X to the reaction to have? Compare the effects of X and of accumulation of P.8. The following data describe the catalysis of cleavage of peptide bonds in small peptides by the enzyme elastase.Substrate K m (mM) k cat (s-1)P A P A↓G 4.0 26P A P A↓A 1.5 37P A P A↓F 0.64 18The arrow indicates the peptide bond cleaved in each case.A.If a mixture of these three substrates was presented to elastase with theconcentration of each peptide equal to 0.5 mM, which would be digested mostrapidly? Which most slowly (Assume enzyme is present in excess.)B.On the basis of these data, suggest what features of amino acid sequence dictate thespecificity of proteolytic cleavage by elastase.C.Elastase is closely related to chymotrypsin. Suggest two kinds of amino acidresidues you might expect to find in or near the active site.9. The serine protease, subtilisin (枯草杆菌蛋白酶), is used in some laundry detergentsto help remove protein-type stains.A. What unusual kind of stability does this suggest for subtilisin.B. Subtilisin does have a problem, in that it becomes inactivated by ox idation of a methionine close to the active site. Suggest a way to make a better subtilisin.10. An enzyme that follows Michaelis-Menten kinetics has a Km of 1 μM. The initialvelocity is 0.1 μM min-1 at a substrate concentration of 100 μM. What is the initialvelocity when [S] is equal toA. 1 mMB. 1 μMC. 2 μM ?11. Regulatory enzymes in metabolic pathways are often found at the first step that isunique to that pathway. How does regulation at this point improve metabolicefficiency?12. There are multiple serine residues in α-chymotrypsin, but only serine 195 reactsrapidly when the enzyme is treated with active phosphate inhibitors such as diisopropyl fluorophosphate (DFP). Explain.13. Distinguish between the lock-and-key and induced-fit models for binding of asubstrate to an enzyme.14. Name three proteins that are subject to the control mechanism of zymogenactivation.15. List the coenzymes that:A. participate as oxidation-reduction reagents.B. act as acyl carriers.C. transfer methyl group.D. transfer groups to and from amino acids.E. are involved in carboxylation or decarboxylation.16. How are coenzymes related to vitamins?Chapter 6. Nucleic AcidsPart I Definitions1.Cyclic nucleotides2. Chargaff’s Rule3. Double Helix4. B- form DNA and Z-form DNA5. 5’-Cap of mRNA6. Denaturation and renaturation7. TmPart II1. A viral DNA is analyzed and found to have the following base composition, in mole percent: A = 32, G = 16, T = 40, C = 12.A. What can you immediately conclude about this DNA?B. What kind of secondary structure do you think it would have?2. Give the following sequence for one strand of a double-strand oligonucleotide:5’ ACCGTAAGGCTTTAG 3’A. Write the sequence for the complementary DNA strand.B. Write the sequence of the RNA complementary to the strand shown above.3. A stretch of double-stranded DNA contains 1000 bp, and its base composition is 58%(G+C). How many thymine residues are in this region of DNA?4. Do the two complementary strands of a segment of DNA have the same base composition? Does (A+G) equal (C+T)?5. In samples of DNA isolated from two unidentified species of bacteria, X and Y, adenine makes up 32% and 17%, respectively, of the total bases. What relative proportions of adenine, guanine, thymine, and cytosine would you expect to find in the two DNA samples? What assumptions have you made? One of these species was isolated from a hot spring (64 C). Suggest which species is the t thermophilic bacterium. What is the basis for your answer?6. Calculate the weight in grams of a double-helical DNA molecule stretching from theearth to the moon (~320,000 km). The DNA double helix weighs about 1 X 1018g per 1,000 nucleotide pairs; each base pair extends 3.4 Å. For an interesting comparison, your body contains about 0.5 g of DNA!7. Compare hydrogen bonding in the αhelix of proteins and in the double helix of DNA. Include the answer the role of hydrogen bonding in stabilizing these two structures.8. Write the structure of cAMP and cGMP molecules.。