📚 Core Topics in Year 11 SQA Biology | SQA 生物 Year 11 核心知识点梳理
This article provides a structured revision guide for Year 11 students following the SQA Biology curriculum. It covers the fundamental topics that are essential for building a deep understanding of life processes, from the molecular level to ecosystems. Each section is presented in both English and Chinese to support bilingual learners, with clear explanations and key facts highlighted.
本文为学习 SQA 生物课程的 Year 11 学生提供系统的复习指南。内容涵盖从分子水平到生态系统的生命过程核心主题，是构建深刻理解所必需的。每个小节均以中英文双语呈现，帮助双语学习者，并突出清晰的解释与关键事实。
1. Cell Structure | 细胞结构
All living organisms are made of cells, which can be prokaryotic (bacteria) or eukaryotic (plants, animals, fungi). Eukaryotic cells contain membrane-bound organelles, each performing specific functions. The nucleus stores genetic information, mitochondria carry out aerobic respiration, ribosomes synthesise proteins, and chloroplasts (in plants) perform photosynthesis. Plant cells also have a rigid cell wall and a large permanent vacuole for support and storage.
所有生物都由细胞组成，细胞分为原核细胞（细菌）和真核细胞（植物、动物、真菌）。真核细胞含有膜结合的细胞器，各司其职。细胞核储存遗传信息，线粒体进行有氧呼吸，核糖体合成蛋白质，叶绿体（植物中）进行光合作用。植物细胞还具有坚硬的细胞壁和一个大液泡，用于支持和储存。
Key cell structures can be summarised in the following table.
下表总结了关键的细胞结构。
| Organelle / 细胞器 | Function / 功能 |
| Nucleus / 细胞核 | Contains DNA, controls cell activities / 含 DNA，控制细胞活动 |
| Mitochondria / 线粒体 | Site of aerobic respiration / 有氧呼吸的场所 |
| Ribosomes / 核糖体 | Protein synthesis / 蛋白质合成 |
| Chloroplasts / 叶绿体 | Photosynthesis (plants only) / 光合作用（仅植物） |
| Cell membrane / 细胞膜 | Controls entry and exit of substances / 控制物质进出 |
2. Transport Across Cell Membranes | 细胞膜运输
The cell membrane is a selectively permeable barrier made of phospholipids and proteins. Small molecules like oxygen and carbon dioxide move by diffusion, down a concentration gradient, requiring no energy. Water moves by osmosis from a dilute solution to a more concentrated solution through a partially permeable membrane. Active transport, in contrast, uses energy from ATP to move substances against the concentration gradient, via carrier proteins.
细胞膜是由磷脂和蛋白质构成的选择性通透屏障。氧气和二氧化碳等小分子通过扩散顺着浓度梯度移动，不需要能量。水通过渗透作用，经部分透性膜从稀溶液向浓溶液移动。主动运输则利用 ATP 的能量，通过载体蛋白将物质逆浓度梯度转运。
Animal cells can burst or shrink if placed in solutions of different water concentrations, while plant cells become turgid or plasmolyzed. In isotonic solutions, cells maintain their normal shape. These principles are critical in medical contexts, such as rehydration therapy.
动物细胞在置于不同水浓度的溶液中时可能涨破或皱缩，而植物细胞则变得硬挺或发生质壁分离。在等渗溶液中，细胞保持正常形状。这些原理在医学环境中（如补液疗法）至关重要。
3. Enzymes | 酶
Enzymes are biological catalysts made of protein that speed up chemical reactions without being consumed. Each enzyme has an active site with a specific shape, complementary to its substrate. This is described by the ‘lock and key’ or ‘induced fit’ model. Enzyme activity is affected by temperature and pH; each enzyme has an optimum. Extremes of temperature or pH can denature the enzyme, changing the shape of the active site permanently.
酶是由蛋白质构成的生物催化剂，能加速化学反应而自身不被消耗。每种酶都有一个具有特定形状的活性位点，与其底物互补，这可用“锁钥模型”或“诱导契合模型”描述。酶的活性受温度和 pH 影响；每种酶都有最适条件。极端的温度或 pH 可使酶变性，永久改变活性位点的形状。
Enzymes are essential in digestion, where amylase breaks down starch, proteases break down proteins, and lipases break down fats. They are also used in industrial processes such as making lactose-free milk and in biological washing powders.
酶在消化中至关重要，淀粉酶分解淀粉，蛋白酶分解蛋白质，脂肪酶分解脂肪。它们也用于工业过程，如制造无乳糖牛奶和生物洗衣粉。
4. DNA and Protein Synthesis | DNA 与蛋白质合成
DNA (deoxyribonucleic acid) is a double helix formed by two strands of nucleotides. Each nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (adenine A, thymine T, cytosine C, guanine G). Base pairing is complementary: A pairs with T, C pairs with G. The sequence of bases forms the genetic code that determines the order of amino acids in a protein.
DNA（脱氧核糖核酸）是由两条核苷酸链组成的双螺旋结构。每个核苷酸由一个磷酸基团、一个脱氧核糖和一个含氮碱基（腺嘌呤 A、胸腺嘧啶 T、胞嘧啶 C、鸟嘌呤 G）组成。碱基配对是互补的：A 与 T 配对，C 与 G 配对。碱基序列构成遗传密码，决定蛋白质中氨基酸的顺序。
Protein synthesis occurs in two main stages: transcription and translation. During transcription, a section of DNA unwinds and mRNA is synthesised using the DNA template. mRNA carries the code to a ribosome where translation takes place. tRNA molecules bring specific amino acids, and the ribosome assembles them into a polypeptide chain. The protein then folds into its functional shape.
蛋白质合成分为两个主要阶段：转录和翻译。转录时，一段 DNA 解开，以 DNA 为模板合成 mRNA。mRNA 将密码携带到核糖体，在此进行翻译。tRNA 分子带来特定的氨基酸，核糖体将其组装成多肽链。随后蛋白质折叠成功能形状。
5. Genetic Engineering | 基因工程
Genetic engineering involves modifying the genome of an organism by inserting a gene from another species to produce a desired characteristic. The process often uses bacterial plasmids as vectors. The required gene is cut out using restriction enzymes, inserted into a plasmid using ligase, and then introduced into a host cell, often by heat shock or electroporation. The host organism then produces the protein coded by the inserted gene.
基因工程涉及通过插入另一物种的基因来改造生物的基因组，以产生所需性状。该过程通常使用细菌质粒作为载体。所需基因用限制性内切酶切下，用连接酶插入质粒，然后引入宿主细胞，通常通过热激或电穿孔。宿主生物随后产生由插入基因编码的蛋白质。
Examples include the production of human insulin by genetically modified bacteria, and the creation of pest-resistant crops by inserting Bt toxin genes. Ethical and safety concerns must be considered, including the potential impact on ecosystems and the need for strict containment.
实例包括利用转基因细菌生产人胰岛素，以及通过插入 Bt 毒素基因培育抗虫作物。必须考虑伦理和安全问题，包括对生态系统的潜在影响以及严格防护的必要性。
6. Cell Division | 细胞分裂
Mitosis is the process by which a cell divides to produce two genetically identical daughter cells. It is essential for growth and repair. The stages are prophase, metaphase, anaphase, and telophase, followed by cytokinesis. In prophase, chromosomes condense; in metaphase, they line up at the equator; in anaphase, sister chromatids are pulled apart; in telophase, new nuclei form. Mitosis maintains the diploid chromosome number.
有丝分裂是细胞分裂产生两个遗传上相同的子细胞的过程，对生长和修复至关重要。其阶段包括前期、中期、后期和末期，随后是胞质分裂。前期染色体凝缩；中期染色体排列在赤道板；后期姐妹染色单体分离；末期形成新核。有丝分裂维持二倍体染色体数目。
In contrast, meiosis produces gametes (sperm and eggs) with half the normal chromosome number (haploid). It involves two divisions, creating genetic variation through crossing over and independent assortment. Fertilisation restores the diploid number.
相比之下，减数分裂产生具有正常染色体数目一半（单倍体）的配子（精子和卵细胞）。它涉及两次分裂，通过交叉互换和自由组合产生遗传变异。受精恢复二倍体数目。
7. Photosynthesis | 光合作用
Photosynthesis is the process by which green plants and some other organisms use light energy to convert carbon dioxide and water into glucose and oxygen. The overall word equation is:
光合作用是绿色植物及某些其他生物利用光能，将二氧化碳和水转化为葡萄糖和氧气的过程。总体文字方程为：
Carbon dioxide + Water → Glucose + Oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
The process occurs in two main stages: the light-dependent reactions in the thylakoid membranes, where light splits water, producing ATP and oxygen; and the Calvin cycle in the stroma, which uses ATP and NADPH to fix CO₂ into glucose. Factors limiting the rate of photosynthesis include light intensity, carbon dioxide concentration, and temperature.
该过程分两个主要阶段：发生在类囊体膜上的光反应，光水解水产生 ATP 和氧气；以及发生在基质中的卡尔文循环，利用 ATP 和 NADPH 将 CO₂ 固定为葡萄糖。限制光合作用速率的因素包括光照强度、二氧化碳浓度和温度。
8. Respiration | 呼吸作用
Respiration is the process of releasing energy from glucose. The energy is stored as ATP (adenosine triphosphate). Aerobic respiration requires oxygen and produces a large amount of ATP, with carbon dioxide and water as by-products.
呼吸作用是从葡萄糖中释放能量的过程。能量以 ATP（三磷酸腺苷）形式储存。有氧呼吸需要氧气，产生大量 ATP，副产物为二氧化碳和水。
Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)
葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量 (ATP)
In the absence of oxygen, cells can undergo anaerobic respiration. In animal cells, this produces lactic acid and a small amount of ATP. In plant and yeast cells, it produces ethanol, carbon dioxide, and a small amount of ATP. The first stage, glycolysis, occurs in the cytoplasm; the later aerobic stages (Krebs cycle and electron transport chain) occur in the mitochondria.
在无氧条件下，细胞可进行无氧呼吸。在动物细胞中，产生乳酸和少量 ATP。在植物和酵母细胞中，产生乙醇、二氧化碳和少量 ATP。第一阶段糖酵解在细胞质中进行；后续的有氧阶段（克雷布斯循环和电子传递链）在线粒体中进行。
9. Nervous System and Hormones | 神经系统与激素
The nervous system uses electrical impulses to coordinate rapid responses. A reflex arc involves a receptor, sensory neuron, relay neuron (in the spinal cord or brain), motor neuron, and effector (muscle or gland). Synapses between neurons use chemicals (neurotransmitters) to transmit signals. The central nervous system (CNS) consists of the brain and spinal cord.
神经系统利用电脉冲协调快速反应。反射弧包括感受器、感觉神经元、联络神经元（脊髓或脑中）、运动神经元和效应器（肌肉或腺体）。神经元之间的突触利用化学物质（神经递质）传递信号。中枢神经系统（CNS）由脑和脊髓组成。
Hormones are chemical messengers released by endocrine glands into the bloodstream, causing slower but longer-lasting effects. Examples include insulin, which lowers blood glucose by stimulating cells to absorb glucose and converting it to glycogen in the liver, and glucagon, which raises blood glucose. Diabetes mellitus type 1 results from the destruction of insulin-producing cells in the pancreas.
激素是由内分泌腺释放到血液中的化学信使，作用较慢但持续时间更长。例如，胰岛素通过刺激细胞吸收葡萄糖并在肝脏中将葡萄糖转化为糖原来降低血糖；胰高血糖素则升高血糖。1型糖尿病是由于胰腺中产生胰岛素的细胞被破坏所致。
10. Ecology and Ecosystems | 生态学与生态系统
An ecosystem consists of a community of organisms interacting with their physical environment. Producers (green plants) convert light energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on other organisms. Energy is lost at each trophic level, mainly as heat from respiration, and only about 10% is transferred to the next level. This is represented in pyramids of energy, biomass, or numbers.
生态系统由生物群落与其物理环境相互作用构成。生产者（绿色植物）通过光合作用将光能转化为化学能。消费者通过摄食其他生物获取能量。能量在每个营养级都会损失，主要以呼吸作用产生的热量形式散失，仅有约 10% 传递到下一级。这用能量金字塔、生物量金字塔或数量金字塔表示。
Key ecological processes include the recycling of carbon and nitrogen. The carbon cycle involves photosynthesis, respiration, combustion, and decomposition. Nitrogen is fixed from the atmosphere by bacteria in root nodules of legumes (rhizobium) or free-living soil bacteria. Decomposers break down organic matter, returning nutrients to the soil.
关键的生态过程包括碳循环和氮循环。碳循环涉及光合作用、呼吸作用、燃烧和分解。氮由豆科植物根瘤中的根瘤菌或土壤中自由生活的细菌从大气中固定。分解者分解有机物，将养分归还土壤。
Sampling techniques such as using quadrats, pitfall traps, and line transects allow biologists to estimate population sizes and distribution of organisms. Biotic factors (competition, predation, disease) and abiotic factors (temperature, pH, light, moisture) affect biodiversity.
采样技术，如使用样方、陷阱和样线，使生物学家能够估计种群大小和生物分布。生物因素（竞争、捕食、疾病）和非生物因素（温度、pH、光照、水分）影响生物多样性。
11. Evolution and Natural Selection | 进化与自然选择
Evolution is the gradual change in the inherited characteristics of a population over many generations. Natural selection, proposed by Charles Darwin, is the mechanism driving evolution. Organisms produce more offspring than can survive; individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.
进化是种群在多个世代中遗传特征的逐渐变化。查尔斯·达尔文提出的自然选择是驱动进化的机制。生物产生的后代数量超过环境承载能力；具有有利性状的个体更可能存活和繁殖，并将这些性状传递给下一代。
Evidence for evolution includes the fossil record, comparative anatomy (homologous structures like pentadactyl limbs), and DNA analysis, showing common ancestry. Speciation occurs when populations become isolated, often by geographical barriers, and then diverge genetically until they can no longer interbreed.
进化的证据包括化石记录、比较解剖学（如同源结构五指附肢）以及 DNA 分析，显示共同祖先。当种群因地理障碍而隔离，随后在遗传上分化直至不再能相互交配，就形成了新物种。
Drug resistance in bacteria (e.g., MRSA) is a rapid form of evolution by natural selection. Overuse of antibiotics kills susceptible bacteria, leaving resistant ones to multiply, presenting a major challenge to human health.
细菌的耐药性（例如 MRSA）是自然选择导致的快速进化形式。滥用抗生素杀死敏感细菌，留下耐药菌繁殖，给人类健康带来重大挑战。
12. Summary of Key Skills and Revision Tips | 关键技能与复习技巧总结
Success in SQA Biology requires not only memorising facts but also applying knowledge to unfamiliar contexts. Practise interpreting graphs related to enzyme activity, photosynthesis rates, and population growth. Be comfortable with experimental design, identifying independent, dependent, and controlled variables. Learn to use biological models such as the fluid mosaic membrane model and the lock-and-key enzyme model. Past paper questions are an excellent resource; attempt them under timed conditions and always read the marking schemes.
在 SQA 生物考试中取得成功不仅需要记忆事实，还需要将知识应用于陌生情境。练习解读与酶活性、光合作用速率和种群增长相关的图表。熟悉实验设计，能识别自变量、因变量和控制变量。学会使用生物学模型，如流动镶嵌膜模型和锁钥酶模型。历年试题是极好的资源；在计时条件下尝试作答，并始终研读评分方案。
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