biochemistry 中国药科大学考研复试专业英语部分

1、Biochemistry is the application of chemistry to the study of biological processes at the cellular and molecular level. Generally speaking it is concerned with the chemistry of those compositions (such as protein, fat, saccharide and nucleic acid )found in living organisms and their metabolic process

2、.Saccharide 糖is a general synonym for sugars. They can be classified as monosaccharide, oligosaccharide少 and polysaccharide. Monosaccharide are the simplest carbohydrates. They cannot be hydrolyzed into simpler sugars. Examples are ribose, glucose, fructose and galactose. Monosaccharides are classif

3、ied by the number of carbon atoms they contain: Triose, Tetrose, Pentose, Hexose, Heptose, Octose, Nonose, Decose,GlucoseFructoseGalactoseRiboseAn oligosaccharide is a saccharide polymer containing a small number (typically three to ten) of component sugars, such as lactose and sucrose.蔗糖 Polysaccha

4、rides are relatively complex carbohydrates. They are polymers made up of many monosaccharides, such as starch淀粉, glycogen 糖原and. As a group, the polysaccharides play diverse and important roles within the biology of life processes; however, they can be divided into two broad groups according to thei

5、r function.Structural polysaccharides (such as cellulose) These polysaccharides are water insoluble and usually perform as strong support material in plants and animals.Storage polysaccharides (such as glycogen)LactosesucroseStarchIn humans and other vertebrates脊椎动物 it is principally stored in the l

6、iver and muscles and is the main form of stored carbohydrate in the body, acting as a reservoir of glucose (which the glycogen can be broken down into) for when the body is being starved of food.According to their component, polysaccharide can be divided intoHomopolysaccharide: polysaccharide formed

7、 from only one kind of monosaccharide. Heteropolysaccharide: polysaccharide formed from different kinds of monosaccharide Proteins are macromolecules大分子 made of amino acids氨基酸 and joined together by peptide肽 bonds between the carboxyl 羧基and amino groups of adjacent amino acid residues. Each amino ac

8、id contains:(1) Carboxyl group (-COO-) (2) Amino group (-NH2) (3) Side chain (R) unique to each amino acid Most proteins fold into 3-dimensinal structures. Primary structure,secondary structure, tertiary structure and quaternary structure.Functions performed by proteins1.Biocatalysis生物催化剂Many protei

9、ns are enzymes that catalyze 向下，反biochemical reactions and are vital有生命的 to metabolism.Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called substrates底物, and the enzyme converts them into different molecules, the products. Cofactors辅因子 and

10、 coenzymes Some enzymes do not need any additional components to show full activity, these enzymes are called simple enzyme。While others require non-protein molecules called cofactors. Cofactors can be either inorganic无机 (such as metal ions离子) or organic compounds (such as vitamin).Those loosely bou

11、nded cofactors which can be eliminated by dialysis透析 are coenzymes, while those tightly bounded cofactors which can not be eliminated by dialysis are prosthetic group辅基. Holoenzyme全 is composed of apoenzyme分离 （酶蛋白）and cofactor.Zymogen or proenzyme 酶原is an active enzyme precursor. such as pepsinogen胃

12、蛋白酶原 and most blood clotting factors involved in coagulation. Inhibitors are molecules that decrease enzyme activity; activators are molecules that increase enzyme activity. Many drugs are enzyme inhibitors.ACEI angiotensin converting enzyme inhibitor-lactamase inhibitor, clavulanic acid (克拉维酸)penic

13、illin2.metabolic regulation代谢调节：many hormones are proteins such as insulin which can regulate blood sugar levels.3.immunol protection免疫保护：antibodies are immunoglobulin4.Transportation运输:Hemoglobin血红蛋白 can transport oxygen and carbon dioxide5.Structural or mechanical functions：Actin肌纤蛋白 and myosin肌球蛋

14、白 in muscleNucleic acidNucleic acid is composed of nucleotide核苷酸. Each nucleotide consists of three components: a nitrogenous heterocyclic 异，杂base,碱基 which is either a purine 嘌呤or a pyrimidine嘧啶; a pentose戊糖; and a phosphate group磷酸基.RNA is ribonucleic acid composed of adenine腺嘌呤, guanine鸟嘌呤, cytosi

15、ne,胞嘧啶 uracil尿嘧啶 and D-ribose. DNA is deoxyribonucleic acid脱氧核糖核酸 composed of adenine, guanine, cytosine ,thymine胸腺嘧啶 and deoxyribose. Both ribose and deoxyribose are pentose. nucleotide monomers form polynucleotide多核苷酸s by phosphodiester bond磷酸二脂键 Two polynucleotides associate to form a double heli

16、x螺螺旋旋 Genetic information is carried by the sequence of base pairsWhat is a gene? Genes are sequences of DNA which serve as blueprints for the production of proteins in all living things. DNA is found in all cells, usually in the nuclei. In bacteria and viruses, which do not have nuclei, the DNA flo

17、ats within the cell. DNA is composed of six molecules: sugars, phosphates磷酸盐 and four bases. A gene produces a specific protein or has an assigned function.What is genetic engineering? Genetic engineering is a process where genetic material (DNA) is taken from one organism and inserted into the cell

18、s of another organism. Genetic engineering also can be the rearrangement of gene location or the removal of genes. The “altered” organism then makes new substances or performs new functions based on its new DNA. For example, the protein insulin, used in the treatment of diabetes, now can be produced

19、 in large quantities by genetically engineered bacteria and yeasts. Insulin was formerly extracted from pigs or cows. Some say the genetic engineering of plants can make food more nutritious and plentiful, helping to feed the ever-rising world population.1. Isolate the gene2. Insert it in a host usi

20、ng a vector3. Produce as many copies of the host as possible4. Separate and purify the product of the geneBasic steps in genetic engineering Endonuclease：Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain, in contrast to exonucleases, which cleave phosphodies

21、ter bonds at the end of a polynucleotide chain. Restriction endonucleases cleave DNA at specific sites 。 DNA ligase： is a special type of ligase that can link together two DNA strands that have double-strand break Vector： is a DNA molecule used as a vehicle to transfer foreign genetic material into

22、another cell. Plasmid：an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA. In many cases, it is circular and double-stranded. Plasmids usually occur naturally in bacteria. From DNA to Protein1.DNA replication: Befor

23、e a cell divides it has to replicate its DNA so that the daughter cell receives a copy of the genome. The DNA helix consists of two complementary DNA strands. Therefore, each of the two strands serves as a template for the construction of the other strand. This process is called semiconservative” re

24、plication. DNA is packed into a compact structure called chromatin. To be able to replicate, the cell has to unfold and unwind the DNA, and also has to separate the two strands from each other. DNA polymerase reads an intact DNA strand as a template and uses it to synthesize the new strand. 2.Transc

25、ription转录 to messenger RNA (mRNA)信使RNA the DNA helix unwinds at a local site where RNA polymerase begin to produce a complementary RNA(mRNA) strand by using DNA as templet.3.RNA processing加工 The transcribed RNA must be modified in several ways before it can be transported out of the nucleus and tran

26、slated into protein. The primary transcription product of a gene is therefore called a precursor前体 of mRNA, pre-mRNA .A major modification is called splicing剪接. Most, but not all eukaryotic真核生物的 genes contain parts that will be present in the mature mRNA, the exons外显子, and parts that will not be par

27、t of the mature mRNA, the introns内含子. Intron: is a DNA region within a gene that is not translated into protein. These non-coding sections are transcribed to precursor mRNA and subsequently removed in splicing.Extron: a DNA region thatcan be translated into protein, it is present in the mature mRNA

28、The nucleotide sequence of the mRNA is composed of four different nucleotides whereas a protein is built up from 20 amino acids. To allow the four nucleotides to specify 20 different amino acids, the nucleotide sequence is interpreted in codons, groups of three nucleotides. These codons have their corresponding anticodon in the tRNA. For example, GCC represent for alanine. 4. Protein translation 蛋白质的翻译 Translation is the actual synthesis of a protein under the dir