📚 Year 12 OCR Biology: Core Knowledge Checklist | Year 12 OCR 生物：核心知识点梳理
A solid grasp of Year 12 OCR Biology lays the groundwork for the entire A level. This checklist covers the essential knowledge areas you will encounter in the first year of the OCR A specification, from the chemistry of life to the complexities of transport and immunity. Use it as a revision map to identify strengths and pinpoint topics that need more focus.
扎实掌握 Year 12 OCR 生物知识是整个 A level 课程的基础。这份清单覆盖了你在 OCR A 考试大纲第一年中会遇到的核心知识领域，从生命的化学基础到复杂的运输和免疫系统。将它作为复习路线图，找出自己的强项，并定位需要重点加强的主题。
1. Cell Structure | 细胞结构
All living organisms are composed of cells, which can be broadly classified as eukaryotic or prokaryotic. Eukaryotic cells contain a true nucleus and membrane-bound organelles, including mitochondria, rough and smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and 80S ribosomes. Prokaryotic cells, such as bacteria, lack these membrane-bound compartments and have smaller 70S ribosomes.
所有生物体都由细胞构成，细胞可大致分为真核细胞和原核细胞。真核细胞含有真正的细胞核和膜包被的细胞器，包括线粒体、粗面和滑面内质网、高尔基体、溶酶体以及 80S 核糖体。原核细胞（如细菌）缺乏这些膜包被结构，并拥有较小的 70S 核糖体。
Microscopy is central to studying cell ultrastructure. Light microscopes can resolve structures down to about 200 nm, while electron microscopes reveal details at the nanometre level, using transmission (TEM) for internal structures and scanning (SEM) for surface topography. Differential centrifugation is used to isolate organelles based on their size and density, with the supernatant containing lighter organelles and the pellet consisting of heavier components.
显微技术是研究细胞超微结构的核心。光学显微镜能分辨约 200 nm 的结构，而电子显微镜可在纳米级别展示细节，透射电镜（TEM）用于观察内部结构，扫描电镜（SEM）用于观察表面形貌。差速离心法根据细胞器的大小和密度将其分离，上清液中含有较轻的细胞器，沉淀物则由较重的组分组成。
2. Biological Molecules | 生物分子
The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Water, although not a macromolecule, is equally essential as a solvent and metabolite. Carbohydrates range from monosaccharides like glucose (α-glucose and β-glucose) to disaccharides (maltose, sucrose, lactose) and polysaccharides (starch, glycogen, cellulose). Their properties arise from glycosidic bonds formed through condensation reactions.
四大类生物大分子分别是碳水化合物、脂质、蛋白质和核酸。水虽然不属于大分子，但作为溶剂和代谢物同样不可或缺。碳水化合物从单糖（如 α-葡萄糖和 β-葡萄糖）到二糖（麦芽糖、蔗糖、乳糖）和多糖（淀粉、糖原、纤维素），其特性源自缩合反应形成的糖苷键。
Lipids include triglycerides, formed by esterification of glycerol and three fatty acids, and phospholipids, which have a hydrophilic head and hydrophobic tails. Proteins are polymers of amino acids linked by peptide bonds. Their primary structure is the amino acid sequence, which folds into secondary (α-helix, β-pleated sheet), tertiary, and quaternary structures. Biuret test detects peptide bonds, Benedict's test detects reducing sugars, and iodine solution identifies starch.
脂质包括由甘油和三个脂肪酸经酯化反应形成的甘油三酯，以及具有亲水性头部和疏水性尾部的磷脂。蛋白质是由氨基酸通过肽键连接而成的聚合物。其一级结构是氨基酸序列，并折叠形成二级结构（α-螺旋、β-折叠）、三级结构和四级结构。双缩脲试验检测肽键，本尼迪克特试验检测还原糖，碘液鉴定淀粉。
3. Enzymes | 酶
Enzymes are globular proteins that act as biological catalysts, lowering activation energy without being consumed. The induced-fit model describes how the active site changes shape slightly to accommodate the substrate, forming an enzyme-substrate complex. The rate of an enzyme-controlled reaction is affected by temperature, pH, enzyme concentration, and substrate concentration.
酶是球状蛋白质，充当生物催化剂，能在自身不被消耗的情况下降低活化能。诱导契合模型描述了活性部位如何轻微改变形状以容纳底物，形成酶-底物复合物。酶促反应的速率受温度、pH、酶浓度和底物浓度的影响。
Inhibitors can reduce enzyme activity reversibly or irreversibly. Competitive inhibitors have a similar shape to the substrate and bind to the active site; their effect can be overcome by increasing substrate concentration. Non-competitive inhibitors bind to an allosteric site, altering the active site's shape. The Michaelis–Menten constant, Kₘ, represents the substrate concentration at half Vₘₐₓ and reflects the affinity of the enzyme for its substrate.
抑制剂可以可逆或不可逆地降低酶活性。竞争性抑制剂形状与底物相似，结合于活性位点；增加底物浓度可以克服其作用。非竞争性抑制剂结合于变构位点，改变活性位点的形状。米氏常数 Kₘ 表示反应速率达 Vₘₐₓ 一半时的底物浓度，反映了酶对底物的亲和力。
4. Nucleic Acids and Protein Synthesis | 核酸与蛋白质合成
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are polymers of nucleotides. Each nucleotide consists of a pentose sugar, a phosphate group, and a nitrogenous base. DNA uses deoxyribose and the bases adenine, thymine, cytosine, and guanine; it is a double helix held together by hydrogen bonds between complementary base pairs (A-T, C-G). RNA uses ribose and replaces thymine with uracil.
脱氧核糖核酸（DNA）和核糖核酸（RNA）是核苷酸的聚合物。每个核苷酸由戊糖、磷酸基团和含氮碱基组成。DNA 的糖为脱氧核糖，碱基为腺嘌呤、胸腺嘧啶、胞嘧啶和鸟嘌呤；它是双螺旋结构，由互补碱基对（A-T、C-G）之间的氢键维持。RNA 使用核糖，并以尿嘧啶代替胸腺嘧啶。
DNA replication is semi-conservative, meaning each new DNA molecule contains one original strand and one newly synthesised strand. The enzyme DNA helicase unwinds the double helix, and DNA polymerase catalyses the formation of phosphodiester bonds between adjacent nucleotides. Protein synthesis involves transcription (DNA to mRNA in the nucleus) and translation (mRNA to polypeptide at ribosomes). The genetic code is degenerate and read as non-overlapping triplet codons.
DNA 复制是半保留的，每个新 DNA 分子都包含一条原始链和一条新合成的链。DNA 解旋酶解开双螺旋，DNA 聚合酶催化相邻核苷酸之间形成磷酸二酯键。蛋白质合成包括转录（细胞核中 DNA 合成 mRNA）和翻译（核糖体上 mRNA 合成多肽）。遗传密码具有简并性，并以不重叠的三联体密码子的形式读取。
5. Cell Membranes and Transport | 细胞膜与跨膜运输
The cell membrane is described by the fluid mosaic model. It consists of a phospholipid bilayer with embedded proteins (intrinsic and extrinsic), cholesterol, glycolipids, and glycoproteins. The fluidity of the membrane is influenced by temperature and the proportion of unsaturated fatty acid tails.
细胞膜可用流动镶嵌模型来描述。它由磷脂双分子层及其中的嵌入蛋白质（内在蛋白和外在蛋白）、胆固醇、糖脂和糖蛋白构成。膜的流动性受温度和不饱和脂肪酸尾部比例的影响。
Movement of substances across membranes occurs via passive or active processes. Simple diffusion and facilitated diffusion (via channel or carrier proteins) are passive and do not require energy. Osmosis is the net movement of water across a partially permeable membrane from a region of higher water potential to a region of lower water potential. Active transport uses carrier proteins and ATP to move substances against their concentration gradient. Endocytosis and exocytosis are used for bulk transport.
物质跨膜运动通过被动或主动过程进行。简单扩散和易化扩散（经由通道蛋白或载体蛋白）是被动的，不需要能量。渗透是水通过部分通透膜从较高水势区域向较低水势区域的净移动。主动运输利用载体蛋白和 ATP 将物质逆浓度梯度运输。胞吞和胞吐用于大块物质的运输。
6. Cell Division and Cellular Organisation | 细胞分裂与组织结构
The cell cycle consists of interphase (G₁, S, G₂) and mitotic phase. During interphase, DNA replicates and the cell synthesises proteins and organelles. Mitosis produces two genetically identical daughter cells and is divided into prophase, metaphase, anaphase, and telophase, followed by cytokinesis. Uncontrolled cell division can lead to cancer.
细胞周期由间期（G₁ 期、S 期、G₂ 期）和分裂期组成。在间期，DNA 复制，细胞合成蛋白质和细胞器。有丝分裂产生两个遗传上相同的子细胞，分为前期、中期、后期和末期，随后进行胞质分裂。不受控制的细胞分裂可能导致癌症。
In multicellular organisms, cells specialise through differentiation to carry out specific functions. Stem cells retain the ability to divide and differentiate. In animals, tissues such as epithelial, connective, muscle, and nervous tissue are organised into organs and organ systems. In plants, meristems contain stem cells that generate new tissues for growth.
在多细胞生物中，细胞通过分化特化来执行特定功能。干细胞保留了分裂和分化的能力。在动物体内，上皮组织、结缔组织、肌肉组织和神经组织等组织构成器官和器官系统。在植物中，分生组织含有干细胞，能够生成用于生长的新组织。
7. Gas Exchange Systems | 气体交换系统
All organisms must exchange oxygen and carbon dioxide with their environment. Single-celled organisms rely on diffusion across their body surface, which is sufficient because their surface area to volume ratio is large. Larger multicellular organisms require specialised exchange surfaces with a large surface area, thin barrier, steep concentration gradient, and good blood supply or ventilation.
所有生物体都必须与环境交换氧气和二氧化碳。单细胞生物依靠通过体表的扩散来满足需求，因为它们的表面积与体积比值较大。较大的多细胞生物则需要特化的交换表面，这些表面必须具备大表面积、薄屏障、陡峭的浓度梯度以及良好的血液供应或通气条件。
In mammals, gas exchange occurs in the alveoli of the lungs. Ventilation maintains a concentration gradient: inspiration involves contraction of the diaphragm and external intercostal muscles, increasing thoracic volume; expiration is largely passive at rest. In bony fish, a counter-current flow between water and blood in the gill lamellae maximises oxygen uptake. Insects use a tracheal system that delivers air directly to tissues, with some species using mechanical ventilation.
在哺乳动物中，气体交换在肺的肺泡中进行。通气维持浓度梯度：吸气涉及膈肌和外肋间肌收缩，胸腔容积增大；呼气在静息时主要被动发生。在硬骨鱼中，水与血液在鳃小片中的逆流机制最大化了氧气的摄取。昆虫利用气管系统将空气直接输送到组织，部分物种还借助机械通气。
8. Transport in Animals | 动物体内的运输
Large organisms need a circulatory system to move substances over long distances. Mammals have a closed, double circulatory system, with the heart acting as a muscular pump. The cardiac cycle includes atrial systole, ventricular systole, and diastole. The sinoatrial node (SAN) initiates the electrical impulse, which spreads to the atrioventricular node (AVN) and along Purkyne tissue.
大型生物体需要循环系统来远距离运输物质。哺乳动物拥有封闭的双循环系统，心脏作为肌肉泵发挥作用。心动周期包括心房收缩期、心室收缩期和舒张期。窦房结（SAN）产生电冲动，冲动传至房室结（AVN）并沿浦肯野组织传导。
Blood vessels are adapted to their roles: arteries carry blood away from the heart under high pressure with thick, elastic walls; veins return blood at low pressure and contain valves; capillaries allow exchange between blood and tissue fluid. Haemoglobin in red blood cells binds oxygen cooperatively, producing a sigmoidal oxygen dissociation curve. The Bohr effect describes how increased carbon dioxide concentration shifts the curve to the right, promoting oxygen release to respiring tissues.
血管与其功能相适应：动脉将血液在高压下带离心脏，管壁厚且有弹性；静脉在低压下将血液送回，内有瓣膜；毛细血管允许血液与组织液之间的交换。红细胞中的血红蛋白协同结合氧气，产生 S 形氧解离曲线。波尔效应描述了二氧化碳浓度增高时曲线右移，促进氧气向呼吸组织释放。
9. Transport in Plants | 植物体内的运输
Plants have two main transport tissues: xylem and phloem. Xylem vessels transport water and dissolved minerals upwards from the roots. They are dead, hollow tubes with thickened walls strengthened by lignin. Transpiration, the evaporation of water from the leaves, creates tension that pulls the water column through the xylem in a process described by the cohesion-tension theory.
植物有两种主要的运输组织：木质部和韧皮部。木质部导管将水和溶解的矿物质从根部向上运输。它们是中空的死细胞管，管壁由木质素加厚加强。蒸腾作用（水分从叶片蒸发）产生张力，通过内聚力-张力机制拉动木质部中的水柱。
Phloem transports assimilates, primarily sucrose, from sources to sinks in a process called translocation. Companion cells provide ATP to actively load sucrose into sieve tube elements at the source, lowering the water potential. Water enters by osmosis, generating high hydrostatic pressure that drives mass flow towards areas of lower pressure at the sink, where sucrose is unloaded. This is known as the mass flow hypothesis.
韧皮部在被称为易位的过程中将同化物（主要是蔗糖）从源运输到库。伴细胞提供 ATP，在源端主动将蔗糖装载到筛管分子中，降低水势。水通过渗透进入，产生高静水压，驱动物质向库端低压区域流动，蔗糖在那里被卸载。这就是压力流动假说。
10. The Immune System and Disease | 免疫系统与疾病
Pathogens such as bacteria, viruses, fungi, and protoctists cause infectious disease. The body has physical and chemical barriers to entry, such as skin and lysozyme in tears. If pathogens breach these barriers, the non-specific inflammatory response mast cells release histamine, causing vasodilation and increased permeability of capillaries.
细菌、病毒、真菌和原生生物等病原体会引起传染病。人体具有物理和化学屏障阻止病原体进入，例如皮肤和眼泪中的溶菌酶。如果病原体突破这些屏障，非特异性的炎症反应中肥大细胞释放组胺，导致血管舒张和毛细血管通透性增加。
The specific immune response involves lymphocytes. B lymphocytes produce antibodies that bind to specific antigens, leading to agglutination and neutralisation. The humoral response involves clonal selection and the production of plasma and memory cells. T helper cells activate B cells and cytotoxic T cells, which kill infected host cells. The primary response is slower, while the secondary response is faster and stronger due to memory cells. Vaccination introduces antigens in a harmless form to stimulate immunity, and antibiotic resistance arises through natural selection when bacteria with resistance genes survive and reproduce.
特异性免疫应答涉及淋巴细胞。B 淋巴细胞产生与特定抗原结合的抗体，导致凝集和中和作用。体液应答包括克隆选择和浆细胞与记忆细胞的产生。辅助 T 细胞激活 B 细胞和细胞毒性 T 细胞，后者杀伤受感染的宿主细胞。初次应答较慢，而二次应答因记忆细胞而更快、更强。疫苗接种以无害形式引入抗原来激发免疫力，而抗生素耐药性则是通过自然选择产生的，当携带耐药基因的细菌存活并繁殖时，耐药性便得以发展。
11. Biodiversity and Classification | 生物多样性与分类
Biodiversity encompasses the variety of living organisms in an area and can be considered at the level of habitat, species, and genetic diversity within a species. Sampling techniques, including random quadrats and transects, are used to estimate population size and distribution. Simpson's Index of Diversity measures species richness and evenness, giving a value between 0 and 1.
生物多样性涵盖某一地区生物的种类多样性，可从栖息地、物种和物种内遗传多样性三个层面考虑。随机样方和样带等取样技术用于估算种群规模和分布。辛普森多样性指数衡量物种丰富度和均匀度，得出 0 到 1 之间的数值。
Classification helps organise biodiversity. The hierarchical system places organisms into domain, kingdom, phylum, class, order, family, genus, and species. The binomial naming system uses the genus and species names. Phylogeny reflects evolutionary relationships, and evidence from DNA sequencing and bioinformatics is now used alongside comparative anatomy to refine classification. Natural selection, driven by variation and competition, leads to evolution and sometimes speciation when populations become reproductively isolated.
分类有助于梳理生物多样性。等级系统将生物归入域、界、门、纲、目、科、属、种。双名法使用属名和种名。系统发育反映了进化关系，现在 DNA 测序和生物信息学的证据与比较解剖学一起被用来完善分类。由变异和竞争驱动的自然选择导致进化，有时当种群产生生殖隔离时便会形成新物种。
12. Practical Skills and Data Analysis | 实验技能与数据分析
Practical work is woven throughout the OCR Biology course. You should be able to design experiments, identify independent, dependent, and control variables, and evaluate limitations. Key practical techniques include microscopy (preparing slides and using an eyepiece graticule), colorimetry (e.g., measuring the progress of enzyme reactions), chromatography (separating photosynthetic pigments), and dissection of plant stems or animal organs.
实验工作贯穿 OCR 生物课程始终。你需要能够设计实验，识别自变量、因变量和控制变量，并评估实验的局限性。关键实验技术包括显微技术（制备装片和使用目镜测微尺）、比色法（例如测量酶反应进程）、色谱法（分离光合色素）以及植物茎或动物器官的解剖。
Data analysis skills are equally important. You must be able to calculate means, standard deviation, and rates from raw data, plot suitable graphs (line, bar, scatter graphs), and draw lines of best fit. Statistical tests such as the chi-squared test (χ² test) for categorical data and Student's t-test for comparing two means may be required. Always relate your conclusions to the biological context and discuss whether results support the original hypothesis.
数据分析技能同样重要。你必须能够从原始数据计算平均值、标准差和速率，绘制合适的图表（线图、条形图、散点图），并画出最佳拟合线。可能会用到统计检验，如用于分类数据的卡方检验和比较两个均值的 Student's t 检验。始终将结论与生物学背景联系起来，并讨论结果是否支持原假设。
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