📚 A-Level Edexcel Biology: Respiration - Key Points Review | A-Level Edexcel 生物：呼吸作用 考点精讲
Respiration is the process by which cells break down organic molecules to release energy, which is used to synthesise ATP, the universal energy currency. In A-Level Edexcel Biology, respiration covers aerobic and anaerobic pathways, the stages of glucose oxidation, chemiosmosis, and respiratory quotients. This article provides an in-depth review of key concepts, exam-relevant details, and common pitfalls.
呼吸作用是细胞分解有机分子、释放能量并合成通用能量货币 ATP 的过程。在 A-Level Edexcel 生物中，呼吸作用涵盖有氧和无氧途径、葡萄糖氧化的各个阶段、化学渗透以及呼吸商。本文将对关键概念、考点细节和常见错误进行深度梳理。
1. Overview of Respiration | 呼吸作用概述
e overall equation for aerobic respiration is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP).
呼吸作用可分为有氧呼吸（需氧）和无氧呼吸（不需氧）。有氧呼吸的总方程式为：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 能量（ATP）。
The energy released is not used directly; it is coupled to ATP synthesis via substrate-level phosphorylation and oxidative phosphorylation. The coenzymes NAD⁺ and FAD act as hydrogen carriers, becoming reduced NAD (NADH) and reduced FAD (FADH₂).
释放的能量并不直接利用，而是通过底物水平磷酸化和氧化磷酸化与 ATP 合成偶联。辅酶 NAD⁺ 和 FAD 作为氢载体，接受氢后分别形成还原型 NAD（NADH）和还原型 FAD（FADH₂）。
Aerobic respiration consists of four main stages: glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation (electron transport chain + chemiosmosis).
有氧呼吸包括四个主要阶段：糖酵解、连接反应、克雷布斯循环和氧化磷酸化（电子传递链 + 化学渗透）。
2. Glycolysis | 糖酵解
Glycolysis occurs in the cytoplasm and does not require oxygen. It splits one 6-carbon glucose (C₆H₁₂O₆) into two 3-carbon pyruvate molecules (C₃H₄O₃).
糖酵解发生在细胞质中，不需氧气。它将一个 6 碳的葡萄糖（C₆H₁₂O₆）分解为两个 3 碳的丙酮酸分子（C₃H₄O₃）。
There is an initial investment of 2 ATP to phosphorylate glucose, making it more reactive. This is followed by lysis and oxidation steps that yield 4 ATP (substrate-level phosphorylation) and 2 NADH. Net gain: 2 ATP and 2 NADH per glucose.
首先消耗 2 分子 ATP 使葡萄糖磷酸化，增加反应活性；随后经过裂解和氧化步骤，通过底物水平磷酸化产生 4 分子 ATP 和 2 分子 NADH。因此每个葡萄糖净得 2 ATP 和 2 NADH。
Key steps: phosphorylation of glucose to hexose bisphosphate, lysis into two triose phosphates, oxidation by removal of hydrogen (donated to NAD⁺), and ATP synthesis from ADP and Pi.
关键步骤：葡萄糖磷酸化生成己糖二磷酸；裂解为两个三碳糖磷酸；脱氢氧化（氢传递给 NAD
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