生物化学复习资料Amino acid（氨基酸）: All proteins are made up from the same set of 20 standard amino acids. A typical amino acid has a primary amino group, a carboxyl group, a hydrogen atom and a side-chain(R group) attached to a central α-group atom(Cα). Proline（脯氨酸）is the exception to the rule in that it has a secondary amino group.Primary structure（一级结构）: The linear（线状的）sequence of amino acids joined together by peptide bonds is termed（被称为）the primary structure of the protein. The position of covalent disulfide bonds between cysteine（半胱氨酸）residues is also included in the primary structure.Secondary structure（二级结构）: Secondary structure is a protein refers to the regular folding of regions of the polypeptide chain. The two most common types of secondary structure are the αhelix and βpleated sheet（β折叠）.Tertiary structure（三级结构）: Tertiary structure in a protein refers to the three-dimensional（三维的）arrangement of all the amino acids in the polypeptide chain. This biologically active, native conformation（构造；形态）is maintained by multiple（多重的；多样的）noncovalent （非共价的）bonds.Quaternary structure（四级结构）: if a protein is made up of more than one polypeptide chain it is said to have quaternary structure. This refers to the spatial（空间的）arrangement of the polypeptide subunits（亚基；亚单位）and the nature of the interactions between them.Protein stability（蛋白质稳定性）: In addition to the peptide bonds between individual amino acid residues, the three-dimensional structure of a protein is maintained by a combination of noncovalent interactions(electrostatic forces（静电力）, van derWaals forces（范德华力）,hydrogen bonds（氢键）, hydrophobic forces（疏水作用力）) and covalent interactions(disulfide bonds（二硫键）).The Bohr effect(波尔效应): H+, CO2and 2,3-bisphosphoglycerate（2,3-二磷酸甘油酸）are allosteric effectors（变构效应剂）, promoting the release of O2 from hemoglobin（血红蛋白）. H+ and CO2 bind to different parts of the polypeptide chains, while 2,3-bisphosphoglycerate binds in the central cavity（凹穴）between the four subunits.Dialysis（透析）: Proteins can be separated from small molecules by dialysis through asemi-permeable membrane（半透膜）which has pores that allow small molecules to pass through but not proteins.Function and diversity of collagen（胶原蛋白）: Collagen is the name given to a family of structurally related proteins that form strong insoluble（不可溶的）fibers. Collagens consist of three polypeptide chains, the identity and distribution of which vary between collagen types.Gel filtration chromatography(凝胶过滤层析)Ion exchange chromatography(离子交换层析)Affinity chromatography(亲和层析)Enzymes as catalysts（作为催化剂的酶）: Enzymes are catalysts（催化剂）that change the rate of a reaction without being changed themselves. Enzymes are highly specific and their activity can be regulated. Virtually all enzymes are proteins, although some catalytically active RNAs have been identified.Active site（活性位点）: The active site is the region of the enzyme that binds the substrate, to form an enzyme-substrate complex, and transforms it into product. The active site is a three-dimensional entity（实体）, often a cleft（裂口）of crevice（缺口）on the surface of the protein, in which the substrate is bound by multiple weak interactions. Two models have been proposed to explain how an enzyme binds its substrate: the lock-and-key model and the induced-fit model（诱导契合模型）.Enzyme classification（酶的分类）: Enzymes are classified into six major groups on the basis of the type of reaction that they catalyze. Each enzyme has a unique four-digit classification number.Enzyme assays（酶的测定）: An enzyme assay measures the conversion of substrate to product, under conditions of cofactors, pH and temperature at which the enzyme is optimally active（最佳活性的）.Coenzymes（辅酶）and prosthetic group（辅基）: Some enzymes require the presence of cofactors, small nonprotein units, to function. Cofactors may be inorganic ions or complex organic molecules called coenzymes. A cofactor that is covalently attached to the enzyme is called a prosthetic group. A holoenzyme is the catalytically active form of the enzyme with its cofactor, whereas an apoenzyme（脱辅基酶蛋白）is the protein part on its own.Isoenzymes（同工酶）: Isoenzymes are different forms of an enzyme which catalyze the same reaction, but which exhibit different physical of kinetic（动力学的）properties（性质）.Activation energy and transition state: For a biochemical reaction to proceed, the energy barrierneeded to transform the substrate molecules into the transition state has to be overcome. The transition state has the highest free energy in the reaction pathway. The different in free energy between the substrate and the transition state is termed the Gibbs free energy of activation. An enzyme stabilizes the transition state and lowers Gibbs free energy（吉布斯自由能）, thus increasing the rate at which the reaction occurs.Michaelis-Menten equation（米氏方程）: v＝Vmax[S]/ (Km+[S])It describe these observations and predicts a hyperbolic curve（双曲线）of V0 against [S]. The Michaelis constant, Km, is equal to the sum of the rates of breakdown of the enzyme-substrate complex over its rate of formation, and is a measure of the affinity（亲和性）of an enzyme for its substrate.Enzyme inhibition（酶的抑制）: The catalytic rate of an enzyme can be lowered by inhibitor molecules. Many inhibitors exist, including normal body metabolites, foreign drugs and toxins. Enzyme inhibition can be of two main types: irreversible or reversible. Reversible inhibition can be subdivided into competitive and noncompetitive.Irreversible inhibition（不可逆抑制）: An irreversible inhibition binds tightly, often covalently, to amino acid residues at the active site of the enzyme, permanently inactivating the enzyme.Reversible competitive inhibition（可逆竞争抑制）: A competitive inhibitor competes with the substrate molecules for binding to the active site of the enzyme. At high substrate concentration, the effect of a competitive inhibitor can be overcome. the type of the inhibition can increase the Km ,but leave the Vmax unchanged.（Km变大，Vmax不变）Reversible noncompetitive inhibition（可逆非竞争性抑制）: A noncompetitive inhibitor binds at a site other than the active site of the enzyme and decreases its catalytic rate by causing a conformational change in the three-dimensional shape of the enzyme. The effect of a noncompetitive inhibitor cannot be overcome at high substrate concentrations. This type of the inhibition can decrease Vmax ,but leave the Km unchanged.（Km不变，Vmax变小）Reversible uncompetitive inhibition（可逆反竞争性抑制）: A uncompetitive inhibition binds at a site located in the substrate-enzyme complex. Thus, the type of the inhibition can decrease both the Vmax and the Km.（Km和Vmax都变小）Allosteric enzymes: A plot（绘制成的坐标图）of V0 against [S] for an allosteric enzyme gives a sigmoidal-shaped curve（S形的曲线）. Allosteric enzymes usually have more than one active site which cooperatively bind substrate molecules, such that the binding of substrate at one active site induces a conformational change in the enzyme which alters the affinity of the other active sites for substrate. Allosteric enzymes are often multisubunit proteins(多亚基蛋白质), with an active site on each subunit. Two models have been proposed to explain the allosteric behavior of enzyme, the concerted or the symmetry model（齐变模型）and the sequential model（序变模型）.Reversible covalent modification: The activity of many enzymes is altered by the reversiblemaking and breaking of a covalent bond between the enzyme and a small nonprotein group. The most common such modification is the addition and removal of a phosphate group（磷酸基）; phosphorylation（磷酸化）and dephosphorylation（去磷酸化）, respectively. Phosphorylation is catalyzed by protein kinases（蛋白激酶）, often using A TP as the phosphate donor, whereas dephosphorylation is catalyzed by protein phosphatases.（蛋白磷酸酯酶或蛋白磷酸化酶）Proteolytic activation（酶原激活）: Some enzymes are synthesized as larger inactive precursors （前体）called proenzymes or zymogens（酶原）. These are activated by the irreversible hydrolysis（水解）of one or more peptide bonds.DNA double helix（DNA双螺旋结构）: In a DNA double helix, the two strands（串；条）of DNA are wound round each other with the bases（碱基）on the inside and the sugar-phosphate backbones（磷酸糖主干）on the outside. The two DNA chains are held together by hydrogen bonds between pairs of bases; adenine（A）always pairs with thymine（T）and guanine（G）always pairs with cytosine（C）. In the double helix, the two strands are organized in an antiparallel arrangement（反平行的排布）(one is oriented in the 5’→3’ , the other is in the 3’→5’).Between the sugar-phosphate strand is the gap which could be divided into two types, that is, the wide named major groove（大沟）and the narrow named minor groove（小沟）.Glycogen（糖原）: glycogen is a branched-chained polysaccharide containing glucose residues linked by α-1-4 bonds（α-1,4糖苷键）with α1-6 branchpoints（α-1,6糖苷键分支点）. The branched nature of glycogen makes it more accessible to glycogen phosphorylase（糖原磷酸化酶）during degradation（降解）, since this enzyme degrades the molecule by sequential removal of glucose residues from the nonreducing ends.Starch（淀粉）: Starch is a mixture of unbranched amylase(glucose residues joined by α1-4 bonds) and branched amylopectin(glucose residues joined α1-4 but with some α1-6 branchpoints).Overview of pentose phosphate pathway（磷酸戊糖途径综述）: The two major products of the pathway are nicotinamide adenine dinucleotide and ribose 5-phosphate（核糖-5-磷酸酯）. Ribose 5-phosphate and its derivatives are components of important cellular molecules such as RNA, DNA, NAD+，flavine adenine dinucleotide(FAD), A TP and coenzyme A(CoA). NADPH is required for many biosynthetic pathways and particularly for synthesis of fatty acids and steroids （类固醇）.Four Biological roles of fatty acids（脂肪酸的四个生理功能）:1.They are components of membranes(sphingolipids and glycerophospholipids)2.Several proteins are covalently modified by fatty acids;3.They act as energy stores(triacylglycerols) and fuel molecules;4.Fatty acid derivatives serve as hormones and intracellular second messengers.Role of Citric acid cycle(柠檬酸循环，又名tricarboxylic acid cycle（三羧酸循环），简称TAC): The cycle oxidizes pyruvate(formed during the glycolytic breakdown of glucose) to CO2andH2O,with the concomitant production of energy. Acetyl CoA from fatty acid breakdown and amino acid degradation products are also oxidaized. In addition, the cycle has a role in producing precursors for biosynthetic pathways.Energy yield of Citric acid cycle（柠檬酸循环的能量产出）: For each turn of the cycle,10 ATP molecules are produced, one directly from the cycle and 9 from the re-oxidation of the three NADH and one FADH2 molecules produced by the cycle by oxidative phosphorylation（氧化磷酸化）.20种常见氨基酸的名称和结构式名称英文缩写结构式甘氨酸(α-氨基乙酸)Glycine Gly GCH2COONH3丙氨酸(α-氨基丙酸)Alanine Ala ACH COONH3CH3亮氨酸(γ-甲基-α-氨基戊酸)*Leucine Leu LCHCOONH3(CH3)2CHCH2异亮氨酸(β-甲基-α-氨基戊酸)* Isoleucine Ile ICHCOONH3CH3CH2CHCH3缬氨酸(β-甲基-α-氨基丁酸)*Valine Val VCHCOONH3(CH3)2CH脯氨酸(α-四氢吡咯甲酸)Proline Pro P COONH H苯丙氨酸(β-苯基-α-氨基丙酸)* Phenylalanine Phe FCHCOONH3CH2蛋(甲硫)氨酸(α-氨基-γ-甲硫基戊酸) * Methionine Met MCHCOONH3CH3SCH2CH2色氨酸[α-氨基-β-(3-吲哚基)丙酸]* Tryptophan Trp WNCH2CH COONH3H丝氨酸(α-氨基-β-羟基丙酸)Serine Ser SCHCOONH3HOCH2谷氨酰胺(α-氨基戊酰胺酸)Glutamine Gln Q CH2CH2CHCOONH3H2N CO苏氨酸(α-氨基-β-羟基丁酸)*Threonine Thr TCHCOONH3CH3CHOH半胱氨酸(α-氨基-β-巯基丙酸)Cysteine Cys CCHCOONH3HSCH2天冬酰胺(α-氨基丁酰胺酸)Asparagine Asn N CH2CHCOONH3H2N CO酪氨酸(α-氨基-β-对羟苯基丙酸) Tyrosine Tyr YCHCOONH3CH2HO天冬氨酸(α-氨基丁二酸) Aspartic acid Asp DNH3HOOCCH2CHCOO谷氨酸(α-氨基戊二酸) Glutamic acid Glu ECHCOONH3HOOCCH2CH2赖氨酸(α,ω-二氨基己酸)*Lysine Lys KCHCOONH2CH2CH2CH2CH2NH3精氨酸(α-氨基-δ-胍基戊酸)Arginine Arg RH2N C CHCOONH2NHCH2CH2CH2NH2组氨酸[α-氨基-β-(4-咪唑基)丙酸] Histidine His H NCH2CH COONH3HN* 为必需氨基酸中性脂肪族氨基酸：Gly (Gly也是二十种中唯一不含手性碳原子的氨基酸，不具有旋光性)Ala Val Lue Ile含羟基或者巯基：Ser Thr Cys Met酸性氨基酸及其酰胺：Asp Asn Glu Gln碱性氨基酸和杂环氨基酸：Lys Arg His Pro芳香族氨基酸：Phe Tyr Trp非极性R基氨基酸：Ala V al Leu Ile Pro Phe Trp Met带正电荷(碱性)R基氨基酸：Lys Arg His不带电荷的极性R基氨基酸：Gly Ser Thr Cys Tyr Asn Gln带负电（酸性）的R基氨基酸：Asp Glu在280nm附近有吸收峰的氨基酸是：Phe Tyr Trp ，其中Trp的吸收峰在280nm处最强等电点：在某一pH的溶液中，氨基酸解离成阳离子和阴离子的趋势及程度相等，所带净电荷为零，呈电中性，此时溶液的pH称为该氨基酸的等电点。