Proteins: Edexcel A-Level Biology Exam Guide | A-Level Edexcel 生物：蛋白质考点精讲

📚 Proteins: Edexcel A-Level Biology Exam Guide | A-Level Edexcel 生物：蛋白质考点精讲

Proteins are fundamental biomolecules that perform a vast array of functions in living organisms, from catalysing metabolic reactions as enzymes to providing structural support. Understanding protein structure and function is a core topic in the Edexcel A-Level Biology syllabus, requiring knowledge of amino acids, peptide bonding, levels of protein organisation, and experimental techniques. This revision guide summarises all essential points to help you master proteins for your exam.

蛋白质是基本的生物分子，在生物体中执行着从酶催化代谢反应到提供结构支撑的广泛功能。理解蛋白质的结构与功能是Edexcel A-Level生物学课程的核心内容，需要掌握氨基酸、肽键、蛋白质组织层次以及实验技术。本复习指南汇总所有关键点，助你考试通关。

1. Amino Acids: The Building Blocks | 氨基酸：蛋白质的基石

All proteins are polymers made up of amino acid monomers. There are 20 standard amino acids, each with the same basic structure: a central (alpha) carbon atom bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a variable R group (side chain). The R group determines the unique properties of each amino acid, such as size, polarity, and charge.

所有蛋白质都是由氨基酸单体组成的聚合物。共有20种标准氨基酸，每种都有相同的基本结构：一个中心（α）碳原子连接着一个氨基（-NH₂）、一个羧基（-COOH）、一个氢原子以及一个可变的R基团（侧链）。R基团决定了每种氨基酸的独特性质，比如大小、极性和电荷。

At physiological pH (around 7.4), the amino group gains a proton to become -NH₃⁺ and the carboxyl group loses a proton to become -COO⁻, giving the amino acid a dipolar ion (zwitterion) form.

在生理pH（约7.4）下，氨基获得一个质子变为-NH₃⁺，羧基失去一个质子

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