📚 Year 13 AQA Biology: Core Concepts Revision | AQA生物核心知识点梳理
Year 13 AQA Biology covers advanced topics that build on foundational knowledge, including energy transfers, genetic control, evolution, and organismal regulation. This article organizes the core concepts into ten focused sections, each pairing concise English explanations with their Chinese equivalents to support bilingual mastery and exam success.
AQA 生物 Year 13 阶段涵盖了许多高级主题，包括能量传递、遗传调控、进化以及生物体调节等内容。本文将这些核心知识点梳理为十个重点小节，每个部分都以简洁的英文讲解搭配对应的中文阐述，帮助双语学习和备考冲刺。
1. Photosynthesis: Light-Dependent and Light-Independent Reactions | 光合作用：光反应与暗反应
The light-dependent reactions take place on the thylakoid membranes of chloroplasts. Photolysis of water releases electrons, protons (H⁺) and O₂. Light energy excites electrons in chlorophyll, which pass along an electron transport chain, generating ATP via chemiosmosis and reducing NADP⁺ to NADPH.
光反应发生在叶绿体的类囊体膜上。水的光解释放电子、质子(H⁺)和氧气。光能激发叶绿素中的电子，电子沿电子传递链传递，通过化学渗透产生 ATP，同时将 NADP⁺ 还原为 NADPH。
The light-independent reactions (Calvin cycle) occur in the stroma. CO₂ combines with ribulose bisphosphate (RuBP) catalysed by Rubisco, producing two molecules of glycerate 3-phosphate (GP). GP is reduced to triose phosphate (TP) using ATP and NADPH from the light-dependent reactions. Some TP regenerates RuBP, while some is used to synthesise glucose and other organic molecules.
暗反应（卡尔文循环）发生在基质中。CO₂ 与核酮糖二磷酸(RuBP)在 Rubisco 催化下结合，生成两分子甘油酸-3-磷酸(GP)。GP 利用光反应产生的 ATP 和 NADPH 被还原为磷酸丙糖(TP)。部分 TP 用于再生 RuBP，另一部分则用于合成葡萄糖和其他有机物。
Limiting factors such as light intensity, CO₂ concentration and temperature influence the rate of photosynthesis. At low light, the light-dependent reactions limit the supply of ATP and NADPH; at low CO₂, Calvin cycle turnover slows. Temperature affects enzyme activity, particularly Rubisco, with an optimum around 25°C for many C₃ plants.
限制因素如光照强度、CO₂ 浓度和温度影响光合作用速率。低光照时，光反应限制 ATP 和 NADPH 的供应；CO₂ 不足时，卡尔文循环周转减慢。温度影响酶活性，尤其是 Rubisco，许多 C₃ 植物的最适温度约为 25°C。
2. Respiration: Glycolysis, Krebs Cycle and Oxidative Phosphorylation | 呼吸作用：糖酵解、克雷布斯循环和氧化磷酸化
Glycolysis takes place in the cytoplasm. Glucose is phosphorylated using 2 ATP, then split into two molecules of triose phosphate, which are oxidised to pyruvate. This yields 2 reduced NAD (NADH) and a net gain of 2 ATP per glucose via substrate-level phosphorylation.
糖酵解发生在细胞质中。葡萄糖先被 2 个 ATP 磷酸化，然后裂解为两分子磷酸丙糖，再氧化为丙酮酸。此过程中，通过底物水平磷酸化，每分子葡萄糖净生成 2 个 ATP，并产生 2 个还原态 NAD (NADH)。
In the mitochondrial matrix, pyruvate is decarboxylated and oxidised to acetyl CoA, releasing CO₂ and reducing NAD⁺ to NADH. Acetyl CoA enters the Krebs cycle, combining with oxaloacetate to form citrate. Through a series of decarboxylations and oxidations, oxaloacetate is regenerated, and further NADH, reduced FAD (FADH₂) and ATP (via GTP) are produced.
在线粒体基质中，丙酮酸脱羧氧化为乙酰辅酶 A，释放 CO₂ 并将 NAD⁺ 还原为 NADH。乙酰辅酶 A 进入克雷布斯循环，与草酰乙酸结合形成柠檬酸。经过一系列脱羧和氧化反应，再生草酰乙酸，同时产生更多的 NADH、还原态 FAD (FADH₂) 以及 ATP（经由 GTP）。
Oxidative phosphorylation occurs on the inner mitochondrial membrane. NADH and FADH₂ donate electrons to the electron transport chain, creating a proton gradient across the membrane. Protons flow back through ATP synthase, driving synthesis of ATP. Oxygen acts as the final electron acceptor, forming water. The total maximum yield is about 38 ATP per glucose, though actual yields are often lower due to proton leakage.
氧化磷酸化发生在线粒体内膜上。NADH 和 FADH₂ 将电子传递给电子传递链，形成跨膜质子梯度。质子通过 ATP 合酶回流，驱动 ATP 合成。氧气作为最终电子受体，生成水。理论上每分子葡萄糖最多产生约 38 个 ATP，但实际因质子泄漏常略低。
3. Energy Transfer in Ecosystems | 生态系统的能量传递
Energy enters most ecosystems as sunlight, captured by autotrophs (producers) during photosynthesis. Gross primary production (GPP) is the total chemical energy fixed. Net primary production (NPP) is GPP minus energy used in respiration (R): NPP = GPP − R. This energy is available to the next trophic level.
能量以太阳光形式进入大多数生态系统，由自养生物（生产者）通过光合作用固定。总初级生产量(GPP)是固定的化学能总量。净初级生产量(NPP)= GPP − 呼吸消耗(R)，这部分能量可供下一营养级使用。
Energy transfer between trophic levels is inefficient, typically 10–20% of available energy is transferred. Losses occur through respiration, heat, undigested material and movement. Pyramids of energy always show a decreasing amount of energy at higher trophic levels. Efficiency = (energy in new biomass at higher level / energy available at lower level) × 100.
营养级之间的能量传递效率很低，通常只有 10–20%。能量因呼吸、散热、未被消化的物质和运动而损失。能量锥体总是表现为高营养级能量递减。传递效率 = (高级别新生物质能量 / 低级别可利用能量) × 100。
Farming practices aim to improve efficiency, e.g. reducing respiratory losses by restricting movement in livestock or keeping animals warmer, or harvesting crops before they are eaten by pests. Such interventions can increase the proportion of energy channelled into human food.
农业实践力求提高能量传递效率，例如通过限制牲畜活动或保暖来减少呼吸消耗，或在作物被害虫吃掉前进行收割。这些干预可增加流向人类食物的能量比例。
4. Nutrient Cycles | 营养循环
The nitrogen cycle involves four key processes: nitrogen fixation, ammonification, nitrification and denitrification. Nitrogen-fixing bacteria (e.g. Rhizobium in root nodules) convert atmospheric N₂ into ammonia/ammonium, which plants can absorb. Free-living soil bacteria like Azotobacter also fix nitrogen.
氮循环包含四个关键过程：固氮作用、氨化作用、硝化作用和反硝化作用。固氮菌（如根瘤中的根瘤菌）将大气 N₂ 转化为氨/铵离子，供植物吸收。土壤中自由生活的固氮菌（如 Azotobacter）也能固氮。
Ammonification is the decomposition of organic nitrogen (e.g. urea, proteins) into ammonium by saprobionts. Nitrification is the oxidation of ammonium to nitrite (NO₂⁻) by Nitrosomonas, then to nitrate (NO₃⁻) by Nitrobacter, both aerobic processes. Denitrification under anaerobic conditions returns nitrate to N₂ gas.
氨化作用指腐生菌将有机氮（如尿素、蛋白质）分解为铵。硝化作用是亚硝化单胞菌将铵氧化为亚硝酸盐(NO₂⁻)，再由硝化杆菌氧化为硝酸盐(NO₃⁻)，两个过程均需氧气。反硝化作用在厌氧条件下将硝酸盐还原为 N₂ 气体。
Leaching of nitrates from soils can lead to eutrophication in waterways. The phosphorus cycle lacks a gaseous phase; phosphorus is released slowly from rock weathering and is often a limiting nutrient in ecosystems. Mycorrhizal fungi increase phosphate uptake by plant roots.
土壤中硝酸盐的淋溶会导致水体富营养化。磷循环没有气态阶段；磷主要通过岩石风化缓慢释放，往往是生态系统中的限制性营养元素。菌根真菌能促进植物根部对磷酸盐的吸收。
5. Inheritance and Hardy-Weinberg Principle | 遗传与哈迪-温伯格原理
Monohybrid and dihybrid crosses follow Mendelian ratios, but many traits exhibit incomplete dominance, co-dominance or multiple alleles. Sex linkage is also tested; for example, haemophilia and colour blindness are X-linked recessive conditions, meaning males are more frequently affected.
单基因杂交和双基因杂交遵循孟德尔比例，但许多性状表现为不完全显性、共显或多等位基因。性连锁也是考点；例如，血友病和红绿色盲是 X 染色体隐性遗传病，男性更易患病。
The Hardy-Weinberg principle describes allele frequencies in a population that is not evolving. For a gene with two alleles, p + q = 1, and genotype frequencies are p² + 2pq + q² = 1. It assumes large population size, random mating, no mutations, no migration and no natural selection.
哈迪-温伯格原理描述了未进化种群中的等位基因频率。对于一对等位基因，p + q = 1，基因型频率 p² + 2pq + q² = 1。其前提假设包括大种群、随机交配、无突变、无迁移、无自然选择。
Calculations often require finding the frequency of the homozygous recessive genotype (q²) from observed data, then deducing q, p, and predicting carrier frequency (2pq). This is used to estimate prevalence of genetic disease carriers in populations.
常见计算题通过观察到的隐性纯合子频率(q²)推算 q、p，进而预测携带者频率(2pq)，用于估算群体中遗传病携带者的比例。
6. Evolution and Speciation | 进化与物种形成
Natural selection acts on phenotypic variation arising from mutation and sexual reproduction. Individuals with advantageous alleles are more likely to survive, reproduce and pass on those alleles, increasing their frequency in the population over generations.
自然选择作用于由突变和有性生殖产生的表型变异。拥有有利等位基因的个体更可能存活、繁殖并将这些等位基因传递下去，导致其频率在种群中逐代增加。
Stabilising selection favours the mean phenotype; directional selection favours one extreme; disruptive selection favours both extremes against the mean, potentially leading to sympatric speciation. Allopatric speciation occurs when populations are geographically isolated, preventing gene flow, and different selection pressures lead to reproductive isolation.
稳定性选择偏向中间表型；定向性选择偏向某一极端；分裂性选择偏向两个极端而淘汰中间型，可能导致同域物种形成。异域物种形成是因地理隔离阻断基因交流，不同的选择压力最终导致生殖隔离。
Reproductive isolation can be prezygotic (temporal, behavioural, mechanical) or postzygotic (hybrid inviability, infertility). The formation of new species is marked by the inability of populations to produce fertile offspring, even if they later come into contact.
生殖隔离可分为合子前隔离（时间、行为、机械隔离）和合子后隔离（杂种不活、不育）。物种形成的标志是即使种群再次接触，也无法产生可育后代。
7. Gene Expression and Epigenetics | 基因表达与表观遗传学
In eukaryotes, transcription is controlled by transcription factors that bind to specific DNA sequences in promoter regions. Activators increase transcription; repressors inhibit it. Oestrogen can act as a transcriptional activator by binding to an oestrogen receptor and facilitating the formation of the transcription initiation complex.
真核生物的转录受转录因子调控，它们与启动子区域的特定 DNA 序列结合。激活因子促进转录，阻遏因子抑制转录。雌激素可作为转录激活物，与雌激素受体结合后，促进转录起始复合物的形成。
Epigenetics involves heritable changes in gene function without altering the DNA base sequence, such as DNA methylation and histone modification. Increased methylation of promoter CpG islands typically silences genes. Histone acetylation reduces the positive charge on histones, loosening chromatin structure and promoting transcription.
表观遗传指不改变 DNA 碱基序列的可遗传的基因功能变化，如 DNA 甲基化和组蛋白修饰。启动子 CpG 岛甲基化增加通常导致基因沉默。组蛋白乙酰化减少组蛋白正电荷，使染色质结构松散，促进转录。
RNA interference (RNAi) is a post-transcriptional control mechanism. Small interfering RNA (siRNA) or microRNA (miRNA) can bind to target mRNA, forming double-stranded regions that are cleaved by RISC or inhibit translation. This provides a way to regulate gene expression by degrading mRNA.
RNA 干扰是转录后调控机制。小干扰 RNA (siRNA) 或微 RNA (miRNA) 能与靶 mRNA 结合，形成双链区域，被 RISC 切割或抑制翻译，从而通过降解 mRNA 来调控基因表达。
8. Recombinant DNA Technology | 重组DNA技术
Recombinant DNA technology involves isolating a gene of interest using reverse transcriptase to produce cDNA from mRNA, or using restriction endonucleases to cut DNA at specific recognition sites, producing sticky or blunt ends. The gene is inserted into a vector, such as a plasmid, using DNA ligase.
重组 DNA 技术包括分离目标基因：可用逆转录酶从 mRNA 产生 cDNA，或用限制性内切酶在特异性识别位点切割 DNA，产生粘性末端或平末端。基因通过 DNA 连接酶插入载体（如质粒）中。
Host cells (often bacteria) are made competent to take up plasmids by heat shock or electroporation. Transformed cells are identified using antibiotic resistance markers and replica plating. The gene can then be expressed to produce a desired protein, e.g. human insulin.
宿主细胞（常为细菌）通过热激或电穿孔处理，以摄取质粒。利用抗生素抗性标记和影印平板筛选转化细胞。然后基因可表达产生目标蛋白，例如人胰岛素。
Polymerase chain reaction (PCR) amplifies DNA in vitro using primers, thermostable DNA polymerase (Taq), and cycles of denaturation (95°C), annealing (55–65°C) and extension (72°C). Gel electrophoresis separates DNA fragments by size, using a standard ladder for comparison. These tools are vital for genetic fingerprinting and diagnosis.
聚合酶链反应(PCR)在体外扩增 DNA，利用引物、耐热 DNA 聚合酶(Taq)，循环进行变性(95°C)、退火(55–65°C)和延伸(72°C)。凝胶电泳按片段大小分离 DNA，用标准阶梯比对。这些工具对基因指纹分析和诊断至关重要。
9. Nervous Coordination: Action Potential and Synapses | 神经协调：动作电位与突触
Resting potential is approximately −70 mV, maintained by the Na⁺/K⁺ pump and differential permeability of the axon membrane to K⁺. Upon stimulation, voltage-gated Na⁺ channels open, causing a rapid influx of Na⁺ and depolarisation. This is followed by opening of voltage-gated K⁺ channels, repolarising the membrane, and a transient hyperpolarisation.
静息电位约为 −70 mV，由 Na⁺/K⁺ 泵和轴突膜对 K⁺ 的选择性通透维持。受刺激后，电压门控 Na⁺ 通道开放，Na⁺ 快速内流引起去极化。随后电压门控 K⁺ 通道开放，膜复极化，并出现短暂的超极化。
The action potential propagates along the axon as local circuits cause adjacent regions to depolarise. In myelinated neurones, saltatory conduction occurs at nodes of Ranvier, greatly increasing the speed of transmission. Factors affecting speed include axon diameter, temperature and myelination.
动作电位沿轴突传播，局部电流使相邻区域去极化。在有髓神经元中，跳跃传导发生在郎飞氏结，大大加快传递速度。影响速度的因素包括轴突直径、温度和髓鞘化程度。
Synaptic transmission involves Ca²⁺ influx into the presynaptic knob, causing vesicles containing neurotransmitter (e.g. acetylcholine) to fuse with the membrane and release their contents. Neurotransmitter diffuses across the cleft and binds to specific receptors on the postsynaptic membrane, opening ligand-gated ion channels. Summation of excitatory and inhibitory inputs determines whether the postsynaptic neurone fires.
突触传递：Ca²⁺ 内流入突触前膜，导致含有神经递质（如乙酰胆碱）的囊泡与膜融合并释放。神经递质扩散过间隙，与突触后膜上的特异性受体结合，开放配体门控离子通道。兴奋性和抑制性输入的叠加决定突触后神经元是否发放冲动。
10. Homeostasis: Blood Glucose and Temperature Regulation | 体内稳态：血糖与体温调节
Blood glucose concentration is regulated by insulin and glucagon from the pancreas. When glucose rises, β-cells of the islets of Langerhans secrete insulin, promoting glucose uptake and glycogenesis in liver and muscle cells. When glucose falls, α-cells secrete glucagon, stimulating glycogenolysis and gluconeogenesis in the liver.
血糖浓度由胰腺分泌的胰岛素和胰高血糖素调节。血糖升高时，胰岛 β 细胞分泌胰岛素，促进肝脏和肌肉细胞摄取葡萄糖和糖原合成。血糖降低时，α 细胞分泌胰高血糖素，刺激肝脏糖原分解和糖异生。
Type 1 diabetes is an autoimmune condition where β-cells are destroyed, requiring insulin injections. Type 2 diabetes involves insulin resistance or reduced insulin secretion, often linked to lifestyle factors. Adrenaline also raises blood glucose by activating glycogenolysis in the liver via cAMP second messenger system.
1 型糖尿病是自身免疫性疾病，β 细胞被破坏，需注射胰岛素。2 型糖尿病涉及胰岛素抵抗或分泌减少，常与生活方式相关。肾上腺素也通过 cAMP 第二信使系统激活肝糖原分解，从而升高血糖。
Thermoregulation is centred on the hypothalamus. In response to cold, peripheral vasoconstriction reduces heat loss, shivering generates heat, and hair erector muscles contract. In heat, vasodilation increases skin blood flow and sweating promotes evaporative cooling. This exemplifies negative feedback mechanisms.
体温调节中枢在下丘脑。遇冷时，外周血管收缩减少散热，战栗产热，立毛肌收缩。遇热时，血管舒张增加皮肤血流，出汗促进蒸发散热。这些体现了负反馈机制。
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