酶如何通过过渡态稳定实现催化？以丝氨酸蛋白酶为例说明。
How do enzymes achieve catalysis by transition-state stabilization? Explain using serine proteases.
酶与底物过渡态的结合亲和力远高于与基态底物或产物的结合，从而显著降低活化能。丝氨酸蛋白酶（如胰凝乳蛋白酶）通过催化三联体（Ser-His-Asp）产氧负离子洞稳定四面体中间体，并借助广义酸碱与共价催化加速肽键水解。这种多重相互作用使反应速率提升约 10⁹–10¹⁰ 倍。
Enzymes bind the transition state far more tightly than the ground-state substrate or product, thereby lowering the activation energy. Serine proteases such as chymotrypsin use a catalytic triad (Ser-His-Asp) and an oxyanion hole to stabilize the tetrahedral intermediate, combining general acid-base and covalent catalysis to speed peptide hydrolysis. These concerted interactions accelerate the reaction by roughly 10⁹–10¹⁰ fold.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
《Nature Chemical Biology》酶学综述；A. Fersht, Structure and Mechanism in Protein Science (1999)
A. Fersht, Structure and Mechanism in Protein Science (1999); Nature Chemical Biology, enzyme mechanism reviews
#酶催化 #过渡态稳定 #丝氨酸蛋白酶 #催化三联体
米氏方程（Michaelis–Menten）描述了什么？其参数 Vmax 和 Km 各有什么物理意义？
What does the Michaelis–Menten equation describe, and what do Vmax and Km physically mean?
米氏方程 v = Vmax[S]/(Km+[S]) 描述单底物酶促反应速率随底物浓度的变化。Vmax 是酶被底物饱和时的最大速率，与酶浓度成正比；Km 是反应速率达到 Vmax 一半时的底物浓度，近似反映酶对底物的亲和力（Km 越小亲和力越高）。该方程基于稳态假设，是酶动力学的基础模型。
The Michaelis–Menten equation v = Vmax[S]/(Km+[S]) describes how the rate of a single-substrate enzyme reaction varies with substrate concentration. Vmax is the maximal rate at saturation and is proportional to enzyme concentration; Km is the substrate concentration at half-maximal rate and approximates affinity (smaller Km means tighter binding). Derived under the steady-state assumption, it is the foundational model of enzyme kinetics.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 酶动力学章；美国化学会(ACS)酶学分会
Lehninger Principles of Biochemistry, 7th ed., enzyme kinetics chapter; ACS Division of Biological Chemistry
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#米氏方程 #酶动力学 #Vmax #Km
血红蛋白是如何结合并运输氧气的？铁在其中起什么作用？
How does hemoglobin bind and transport oxygen, and what role does iron play?
血红蛋白是由四个亚基组成的金属蛋白，每个亚基含一个以血红素为辅基的亚铁（Fe²⁺）中心。Fe²⁺ 位于卟啉环中央，可逆地配位一个氧分子而不被氧化为 Fe³⁺。脱氧与氧合状态的构象变化产生协同效应，使肺部高氧时易结合、组织中低氧时易释放。
Hemoglobin is a metalloprotein of four subunits, each carrying an iron(II) heme cofactor. The Fe²⁺ sits at the center of a porphyrin ring and binds one O₂ reversibly without being oxidized to Fe³⁺. Conformational changes between deoxy and oxy states create cooperativity, so oxygen is taken up readily in the lungs and released in oxygen-poor tissues.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 蛋白质章；中国科学院生物物理研究所
Lehninger Principles of Biochemistry, 7th ed., protein chapter; Nature Structural & Molecular Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#血红蛋白 #血红素 #铁 #氧运输
抗体的化学本质是什么？它如何识别抗原？
What is the chemical nature of antibodies, and how do they recognize antigens?
抗体是糖蛋白，基本结构为四条多肽链（两条重链、两条轻链）经二硫键连接成 Y 形。其可变区氨基酸序列高度多样，通过互补决定区（CDR）以非共价作用力（氢键、疏水、静电）特异性结合抗原表位。这种结构基础使免疫系统能识别海量外来分子。
Antibodies are glycoproteins built from four polypeptide chains (two heavy and two light) linked by disulfide bonds into a Y shape. Their variable regions are highly diverse, and the complementarity-determining regions (CDRs) specifically bind antigen epitopes through noncovalent forces such as hydrogen bonding, hydrophobic, and electrostatic interactions. This architecture lets the immune system recognize a vast array of foreign molecules.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 免疫系统章；Nature Immunology
Lehninger Principles of Biochemistry, 7th ed., immune system chapter; Nature Immunology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#抗体 #糖蛋白 #抗原 #可变区
什么是酶固定化？它在实际应用中带来哪些好处？
What is enzyme immobilization, and what practical benefits does it bring?
酶固定化是将游离酶通过吸附、包埋、共价交联或载体结合等方式固定于不溶性支持物上的技术。固定化酶稳定性更高、可重复使用、易于与产物分离，并能装填于连续反应柱中实现工业化催化。它在食品、医药和传感领域应用广泛。
Enzyme immobilization attaches free enzymes to insoluble supports by adsorption, entrapment, covalent cross-linking, or carrier binding. Immobilized enzymes are more stable, reusable, and easy to separate from products, and can be packed into continuous-flow reactors for industrial catalysis. They are widely used in food, pharmaceutical, and sensor applications.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
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Buchholz, Kasche & Bornscheuer《生物催化剂与酶技术》（Biocatalysts and Enzyme Technology）
Buchholz, Kasche & Bornscheuer, "Biocatalysts and Enzyme Technology"
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL13638213W：Biocatalysts and enzym
#酶固定化 #固定化酶 #生物催化 #连续反应
辅酶和辅基有什么区别？它们在酶催化中起什么作用？
What is the difference between a coenzyme and a prosthetic group, and what role do they play in catalysis?
辅酶是与酶蛋白松散结合、反应中可解离扩散的小分子有机辅助因子（如 NAD⁺、CoA）；辅基则通过共价或强非共价作用牢固结合在酶上（如血红素、FAD）。二者常作为电子、基团或原子的载体，扩展酶的活性中心化学能力。缺少它们，许多酶将失去催化活性。
A coenzyme binds loosely to the enzyme and can dissociate during the reaction (e.g., NAD⁺, CoA), whereas a prosthetic group is tightly and often covalently attached (e.g., heme, FAD). Both act as carriers of electrons, groups, or atoms, extending the chemical repertoire of the active site. Without them many enzymes are inactive.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 酶章；IUPAC（生物化学术语）
Lehninger Principles of Biochemistry, 7th ed., enzyme chapter; IUPAC Biochemical Nomenclature
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#辅酶 #辅基 #辅助因子 #酶催化
什么是竞争性抑制剂？它如何影响酶的动力学参数？
What is a competitive inhibitor, and how does it affect an enzyme's kinetic parameters?
竞争性抑制剂与底物结构相似，争夺同一活性位点，因而提高表观 Km 而 Vmax 不变。随着底物浓度增大，底物可在竞争中胜出，抑制作用被解除。典型的例子是丙二酸对琥珀酸脱氢酶的抑制。
A competitive inhibitor resembles the substrate and competes for the same active site, raising the apparent Km while leaving Vmax unchanged. At high substrate concentration the substrate outcompetes the inhibitor, so inhibition is overcome. A classic example is malonate inhibiting succinate dehydrogenase.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 酶调节章；IUPAC（生物化学术语）
Lehninger Principles of Biochemistry, 7th ed., enzyme regulation chapter; IUPAC Biochemical Nomenclature
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#竞争性抑制 #酶抑制剂 #活性位点 #Km
为什么 ATP 水解能驱动细胞做功？释放的能量来自哪里？
Why can ATP hydrolysis drive cellular work, and where does the released energy come from?
ATP 水解为 ADP 与磷酸时释放约 -30.5 kJ/mol 的标准自由能，主要来自产物中磷酸根基团更好的共振稳定与溶剂化，以及反应中静电排斥的减小。细胞把这一放能过程与吸能过程（如物质合成、主动运输）偶联，从而驱动生命活动。
ATP hydrolysis to ADP and phosphate releases about -30.5 kJ/mol of standard free energy, mainly because the products are better stabilized by resonance and solvation and carry less electrostatic repulsion. Cells couple this exergonic step to endergonic processes such as biosynthesis and active transport to power life.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
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《生物化学》(Lehninger, 第七版) 生物能量学章；Nature Reviews Molecular Cell Biology
Lehninger Principles of Biochemistry, 7th ed., bioenergetics chapter; Nature Reviews Molecular Cell Biology
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-319-45541-5 (8th ed., Macmillan Learning)
#ATP #自由能 #能量偶联 #水解