Enzymes: The Biological Catalysts | 酶：生物催化剂

📚 Enzymes: The Biological Catalysts | 酶：生物催化剂

Enzymes are biological molecules that speed up chemical reactions in living organisms. They are essential for life, enabling processes such as digestion, respiration, and photosynthesis to occur at rates fast enough for survival.

酶是生物体内加速化学反应的大分子。它们对生命至关重要，使消化、呼吸和光合作用等过程以足够快的速度发生以维持生存。

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1. What Are Enzymes? | 什么是酶？

Enzymes are proteins, made of chains of amino acids folded into a specific 3D shape. Each enzyme has an active site, a region where reactants (substrates) bind.

酶是蛋白质，由氨基酸链折叠成特定的三维形状。每个酶有一个活性位点，即反应物（底物）结合的区域。

Enzymes are specific – they only catalyse one reaction or type of reaction because the active site is complementary to the substrate.

酶具有专一性——它们只催化一种或一类反应，因为活性位点与底物互补。

• Lock and key model – active site shape is fixed.
• Induced fit model – active site changes shape slightly to fit substrate.

• 锁钥模型——活性位点形状固定。
• 诱导契合模型——活性位点形状稍变以适应底物。

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2. Enzyme Structure and Function | 酶的结构与功能

Enzymes lower the activation energy of a reaction by providing an alternative pathway. This means reactions require less energy to start.

酶通过提供替代途径降低反应的活化能。这意味着反应启动所需能量更少。

In the reaction, the substrate binds to the active site, forming an enzyme-substrate complex. Then the enzyme catalyses the conversion into products, which are released.

在反应中，底物结合到活性位点，形成酶-底物复合物。然后酶催化转化为产物，产物释放。

E + S → ES → E + P

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3. The Effect of Temperature | 温度的影响

Temperature affects enzyme activity. As temperature increases, particles gain kinetic energy, so collisions between enzyme and substrate increase, raising the reaction rate. However, above an optimum temperature, the enzyme denatures.

温度影响酶的活性。温度升高，粒子获得动能，酶与底物碰撞增加，反应速率升高。但超过最适温度后，酶发生变性。

The optimum temperature for most human enzymes is around 37°C (body temperature).

大多数人酶的最适温度约为37°C（体温）。

Denaturation occurs when the enzyme’s 3D structure is disrupted, particularly the active site, so the substrate no longer fits. This is often irreversible.

变性是指酶的三维结构被破坏，尤其是活性位点，底物不再匹配。这通常是不可逆的。

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4. The Effect of pH | pH的影响

Each enzyme has an optimum pH. Changes in pH affect the charge and shape of the active site.

每种酶都有最适pH。pH变化影响活性位点的电荷和形状。

At extremes of pH, enzymes denature. For example, pepsin in the stomach works best at pH 2, while trypsin in the small intestine works best at pH 8.

在极端pH下，酶变性。例如胃中的胃蛋白酶在pH2时最佳，小肠中的胰蛋白酶在pH8时最佳。

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5. Enzyme Concentration | 酶浓度

As enzyme concentration increases, the rate of reaction increases, provided there is enough substrate. However, if substrate becomes limiting, the rate levels off.

随着酶浓度增加，反应速率增加，前提是有足够底物。然而，如果底物成为限制因素，速率趋于平稳。

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6. Substrate Concentration | 底物浓度

Increasing substrate concentration increases reaction rate until the active sites of all enzyme molecules are occupied. At this point, adding more substrate has no effect.

增加底物浓度会提高反应速率，直到所有酶分子的活性位点都被占用。此时，再加底物也没有作用。

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7. Inhibitors | 抑制剂

Inhibitors are molecules that reduce enzyme activity. They are classified as competitive or non-competitive.

抑制剂是降低酶活性的分子，分为竞争性和非竞争性。

• Competitive inhibitors – have a similar shape to the substrate and block the active site. Increasing substrate concentration overcomes them.
• Non-competitive inhibitors – bind to another part of the enzyme (allosteric site), changing the active site shape so substrate cannot bind.

• 竞争性抑制剂——形状与底物相似，占据活性位点。增加底物浓度可克服它们。
• 非竞争性抑制剂——结合到酶的其他部位（别构位点），改变活性位点形状使底物无法结合。

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8. Uses of Enzymes in Industry | 酶在工业中的应用

Enzymes are widely used in biotechnology, food, and medicine.

酶广泛用于生物技术、食品和医药。

Enzyme | 酶	Use | 用途
Protease | 蛋白酶	Making biological washing powders; removing stains | 制造生物洗衣粉；去除污渍
Amylase | 淀粉酶	Converting starch to sugar for syrups | 将淀粉转化为糖用于糖浆
Pectinase | 果胶酶	Clarifying fruit juices | 澄清果汁
Lactase | 乳糖酶	Producing lactose-free milk | 生产无乳糖牛奶

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9. Immobilised Enzymes | 固定化酶

Immobilised enzymes are attached to an inert support, allowing them to be reused and easily separated from products. This increases efficiency and reduces cost.

固定化酶附着在惰性载体上，可重复使用并易与产物分离，提高效率并降低成本。

An example is using immobilised glucose isomerase to convert glucose into fructose in syrup production.

例如使用固定化葡萄糖异构酶在糖浆生产中将葡萄糖转化为果糖。

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10. Enzymes in Digestion | 消化中的酶

Digestive enzymes break down large food molecules into smaller soluble molecules that can be absorbed.

消化酶将大分子食物分解成可吸收的小分子可溶性物质。

• Amylase converts starch → maltose
• Proteases convert proteins → amino acids
• Lipase converts lipids → fatty acids and glycerol

• 淀粉酶：淀粉 → 麦芽糖
• 蛋白酶：蛋白质 → 氨基酸
• 脂肪酶：脂质 → 脂肪酸和甘油

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Published by TutorHao | Biology Revision Series | aleveler.com

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