复习题2016生物化学

一、解释名词

必需氨基酸、非编码氨基酸、氨基酸残基、亚基、简单蛋白、缀合蛋白、肽链、

蛋白质的一级结构、蛋白质的二级结构、蛋白质的三级结构、蛋白质的四级结构、蛋白质的等电点、Edman降解

二、简答问题

1.简述蛋白质一级结构的解析方法。

2.简述蛋白质N-端序列分析方法。

3.简述常用于肽链裂解的蛋白酶有哪些？有哪些特征？

4.比较由蛋白质水解获得氨基酸的方法与特征？

5.阐述蛋白质定性和定量分析的方法和原理？

三、思考题

某一条肽链经酸水解后，分析其组成成分含5种氨基酸，其N-端非常容易环化。经CNBr 处理后得到以游离的碱性氨基酸，Pauly反应呈阳性。若用胰蛋白酶作用则得到两个肽段；其一为坂口反应阳性，另一个在280nm有强的光吸收，并呈Millon氏阳性反应。

求此肽的氨基酸排列顺序，并指出它的等电点（pI）应该是大于、等于或小于pH7。

一、解释名词

肽平面、拉氏构象图、蛋白质的二级结构/三级结构/四级结构、模体（motif）、结构域、超二级结构、蛋白质折叠、蛋白质分子伴侣、蛋白质的变形与复性、蛋白质组、蛋白质组学

二、简答问题

1．稳定蛋白质三维结构的作用力主要有哪些？

2．比较蛋白质的二级结构/三级结构/四级结构的异同？

3．影响蛋白质的二级结构稳定性的主要因素有哪些？请说明理由。

4．蛋白质产生四级结构的意义是什么？

5．蛋白质折叠的基本规律？

三、思考题

1．试描述蛋白质折叠的全过程。

2．蛋白质的变形与复性有何异同？

3．蛋白质组学研究的内容和基本方法？

4．疯牛病是有病毒引起的传染性疾病，你是否同意？请说明理由。

5．已知分子量为240000的蛋白质多肽链的一些节段是α螺旋，而另一些节段是β-折叠，其分子展开长度为5.06X10-5cm。试问该肽分子中α螺旋和β-折叠的百分率。四、 翻译成中文

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

一、解释名词

电泳、等电聚焦电泳、双向电泳、离子交换层析、疏水作用层析、亲和层析、聚焦层析、凝胶过滤层析、沉降系数

二、简答问题

1.SDS-PAGE是何含义，其基本原理是什么？有哪些应用？

2.在蛋白质一级结构分析中，如何定位二硫键？

3.依制备用离心机的转速，如何划分低速、高速和超速离心机？

4.多肽固相合成的基本原理是什么？

三、思考题

1.试描述蛋白质分离和纯化的常用方法和纯化方案设计的基本思路。

2.如何鉴定得到的蛋白质是已经纯化的？

3.如何鉴定得到的蛋白质的分子量？如何区分是单体蛋白或寡聚蛋白？

4.凝胶过滤和SDS-凝胶电泳有何不同？

四、 翻译成中文

Protein purification purpose

The purpose of Protein purification is either preparative or analytical. Preparative purifications aim to produce a relatively large quantity of purified proteins for subsequent use. Examples include the preparation of commercial products such as enzymes (e.g. lactase), nutritional proteins (e.g. soy protein isolate), and certain biopharmaceuticals (e.g. insulin). Analytical purification produces a relatively small amount of a protein for a variety of research or analytical purposes, including identification, quantification, and studies of the protein's structure, post-translational modifications and function. Pepsin and urease were the first proteins purified to the point that they could be crystallized.

Purification strategies

Choice of a starting material is key to the design of a purification process. In a plant or animal, a particular protein usually isn't distributed homogeneously throughout the body; different organs or tissues have higher or lower concentrations of the protein. Use of only the tissues or organs with the highest concentration decreases the volumes needed to produce a given amount of purified protein. If the protein is present in low abundance, or if it has a high value, scientists may use recombinant DNA technology to develop cells that will produce large quantities of the desired protein (this is known as an expression system). Recombinant expression allows the protein to be tagged, e.g. by a His-tag,

to facilitate purification, which means that the purification can be done in fewer steps. In addition, recombinant expression usually starts with a higher fraction of the desired protein than is present in a natural source.

An analytical purification generally utilizes three properties to separate proteins. First, proteins may be purified according to their isoelectric points by running them through a pH graded gel or an ion exchange column. Second, proteins can be separated according to their size or molecular weight via size exclusion chromatography or by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) analysis. Proteins are often purified by using 2D-PAGE and are then analysed by peptide mass fingerprinting to establish the protein identity. This is very useful for scientific purposes and the detection limits for protein are nowadays very low and nanogram amounts of protein are sufficient for their analysis. Thirdly, proteins may be separated by polarity/hydrophobicity via high performance liquid chromatography or reversed-phase chromatography.

Usually a protein purification protocol contains one or more chromatographic steps. The basic procedure in chromatography is to flow the solution containing the protein through a column packed with various materials. Different proteins interact differently with the column material, and can thus be separated by the time required to pass the column, or the conditions required to elute the protein from the column. Usually proteins are detected as they are coming off the column by their absorbance at 280 nm.

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2016-10-18

一、解释名词

别构效应、别构蛋白、别构剂、协同效应、波尔效应、分子病

二、简答问题

血红蛋白正协同效应的两种模型是什么？

镰刀状细胞贫血病(sickle-cell anemia）的分子机制

H+、CO2和BPG 对血红蛋白结合氧的影响及机制

蛋白质进化的四种情形

三、思考题

试比较肌红蛋白和血红蛋白结构和功能的异同。

试描述肌肉收缩的分子机制。

以血红蛋白结合氧的机制为例，阐述蛋白质结构与功能的关系

四、 翻译成中文

Protein structure is the three-dimensional arrangement of atoms in a protein molecule. Proteins are polymers— specifically polypeptides—formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may also be called a residue (chemistry) indicating a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond. By convention, a chain under 30 amino acids is often identified as a peptide, rather than a protein.[1]To be able to perform their biological function, proteins fold into one or more specific spatial conformations driven by a number of non-covalent interactions such as hydrogen bonding, ionic interactions, Van der Waals forces, and hydrophobic packing. To understand the functions of proteins at a molecular level, it is often necessary to determine their three-dimensional structure. This is the topic of the scientific field of structural biology, which employs techniques such as X-ray crystallography, NMR spectroscopy, and dual polarisation interferometry to determine the structure of proteins.

Protein structures range in size from tens to several thousand amino acids.[2] By physical size, proteins are classified as nanoparticles, between 1–100 nm. Very large aggregates can be formed from protein subunits. For example, many thousands of actin molecules assemble into a microfilament.

A protein may undergo reversible structural changes in performing its biological function. The alternative structures of the same protein are referred to as different conformational isomers, or simply, conformations, and transitions between them are called conformational changes.

2016-10-24

一、解释名词

酶、别构酶、酶活力、酶的比活性、核酶、抗体酶、酶工程、酶的失活、酶的抑制作用、酶的可逆抑制、酶的不可逆抑制

二、简答问题

1.作为生物催化剂酶的特性是什么？

2.酶的诱导契合假说的内容是什么？

3.举例说明三种可逆抑制的特点？酶的可逆抑制剂对酶Vm和Km的影响有哪些？

三、思考题

1.请根据平衡学说和稳态学说，推导两种假设条件下的米氏方程，并讨论Km值的意义。

2.将某一小鼠肝脏组织制成匀浆得粗酶溶液100ml，测其蛋白浓度是

3.2mg/ml，取其10

微升测得催化底物转化速率为每分钟0.14微摩尔；将上述粗酶溶液用硫酸铵盐析，得到的沉淀再溶于10ml缓冲液中，测得其蛋白浓度是23mg/ml，取其10微升测得催化底物转化速率为每分钟8.9微摩尔。请计算：该提取过程，酶的回收率？酶的提纯倍数？

四、 翻译成中文

Enzymes are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions. The molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life. The set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology.

Enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules. Enzymes' specificity comes from their unique three-dimensional structures.

Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy. Some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5'-phosphate decarboxylase, which allows a reaction that would otherwise take millions of years to occur in milliseconds. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. Enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity.

Many drugs and poisons are enzyme inhibitors. An enzyme's activity decreases markedly outside its optimal temperature and pH.

Some enzymes are used commercially, for example, in the synthesis of antibiotics. Some household products use enzymes to speed up chemical reactions: enzymes in biological washing powders break down protein, starch or fat stains on clothes, and enzymes in meat tenderizer break down proteins into smaller molecules, making the meat easier to chew.

2016-11-1

一、解释名词

酶的活性中心、酶的邻近效应、酶的定向效应、酶原、酶原的激活、蛋白激酶、

蛋白磷酸化酶、同工酶、辅酶

二、简答问题

1.酶活性部位的特点是什么？与酶活性必须基团的关系如何？

2.丝氨酸蛋白酶的催化三联体是什么？

3.举例说明酶原激活的机理和生物学意义？

4.真核生物蛋白激酶的分类有哪些？说明蛋白激酶A的激活原理。

5.举例说明同工酶的特点与生理意义。

三、思考题

见教材P253-254 思考题9、10、11、12、13、14

四、 翻译成中文

A vitamin is an organic compound and a vital nutrient that an organism requires in limited

amounts. An organic chemical compound (or related set of compounds) is called a vitamin when the organism cannot synthesize the compound in sufficient quantities, and it must be obtained through the diet; thus, the term "vitamin" is conditional upon the circumstances and the particular organism. For example, ascorbic acid (one form of vitamin C) is a vitamin for humans, but not for most other animal organisms. Supplementation is important for the treatment of certain health problems, but there is little evidence of nutritional benefit when used by otherwise healthy people

Vitamins have diverse biochemical functions. Some, such as vitamin D, have hormone-like functions as regulators of mineral metabolism, or regulators of cell and tissue growth and differentiation (such as some forms of vitamin A). Others function as antioxidants(e.g., vitamin E and sometimes vitamin C). The largest number of vitamins, the B complex vitamins, function as enzyme cofactors(coenzymes) or the precursors for them; coenzymes help enzymes in their work as catalysts in metabolism. In this role, vitamins may be tightly bound to enzymes as part of prosthetic groups: For example, biotin is part of enzymes involved in making fatty acids. They may also be less tightly bound to enzyme catalysts as coenzymes, detachable molecules that function to carry chemical groups or electrons between molecules. For example, folic acid may carry methyl, formyl, and methylene groups in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins' best-known function, the other vitamin functions are equally important.