📚 Core Concepts Review for Year 12 WJEC Biology | Year 12 WJEC 生物：核心知识点梳理
This article distills the essential topics from the Year 12 WJEC Biology specification into a structured, bilingual revision guide. It covers the building blocks of life, cell organisation, genetic continuity, and the physiology of transport and defence systems. Each section pairs key English explanations with their Chinese equivalents to reinforce understanding and aid memorisation.
本文从 Year 12 WJEC 生物学大纲中提炼出核心主题，整理成结构化的双语复习指南。内容涵盖生命的构建模块、细胞组织、遗传连续性以及物质运输和防御系统的生理学。每个部分都将关键的英文解释与中文对应，以加深理解并辅助记忆。
1. Biological Molecules: Carbohydrates and Lipids | 生物分子：碳水化合物与脂质
Monosaccharides are the simplest carbohydrates, with the general formula (CH₂O)n, where n is usually between 3 and 7. Glucose, a hexose, has the molecular formula C₆H₁₂O₆.
单糖是最简单的碳水化合物，通式为(CH₂O)n，其中n通常在3到7之间。葡萄糖是一种己糖，分子式为C₆H₁₂O₆。
Glucose exists as two isomers, α-glucose and β-glucose, which differ in the orientation of the hydroxyl group (-OH) on carbon atom 1. This small difference has major consequences for polymer structure.
葡萄糖存在两种异构体，α-葡萄糖和β-葡萄糖，它们在1号碳原子上的羟基(-OH)取向不同。这个微小差异对聚合物的结构有重大影响。
A condensation reaction between two monosaccharides forms a glycosidic bond and releases water. Maltose, for example, is a disaccharide produced from two α-glucose molecules.
两个单糖之间发生缩合反应，形成糖苷键并释放水。例如，麦芽糖是由两个α-葡萄糖分子生成的二糖。
Polysaccharides are polymers of monosaccharides. Starch, made of amylose (unbranched, helical) and amylopectin (branched), is the main energy store in plants. Glycogen is highly branched and serves as the animal storage polysaccharide.
多糖是单糖的聚合物。淀粉由直链淀粉（无分支、螺旋状）和支链淀粉（有分支）组成，是植物的主要储能物质。糖原高度分支，是动物的储存多糖。
Triglycerides are lipids formed by ester bonds between one glycerol molecule and three fatty acids. They are hydrophobic and efficient energy stores.
甘油三酯是由一个甘油分子与三个脂肪酸之间通过酯键形成的脂质。它们具有疏水性，是高效的能量储存分子。
). The double bonds introduce kinks, preventing tight packing and lowering melting points.
脂肪酸可以是饱和的（无碳碳双键）或不饱和的（含一个或多个碳碳双键）。双键引起链的弯折，阻止紧密排列，从而降低熔点。
2. Proteins and Enzymes | 蛋白质与酶
Amino acids are the monomers of proteins, sharing a common structure: an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and a variable R group, all attached to a central α-carbon.
氨基酸是蛋白质的单体，具有共同结构：一个氨基(NH₂)、一个羧基(COOH)、一个氢原子和一个可变的R基团，全部连接在中心α碳上。
Polypeptides form through condensation reactions that create peptide bonds between the carboxyl group of one amino acid and the amino group of another.
多肽通过缩合反应形成，该反应在一个氨基酸的羧基与另一个氨基酸的氨基之间生成肽键。
Protein structure is described at four levels: primary (amino acid sequence), secondary (α-helices and β-pleated sheets due to hydrogen bonding), tertiary (3D folding due to R group interactions), and quaternary (assembly of multiple polypeptide chains).
蛋白质结构分为四个层次：一级结构（氨基酸序列）、二级结构（由氢键形成的α-螺旋和β-折叠片）、三级结构（由R基团相互作用导致的三维折叠）和四级结构（多条多肽链的组装）。
Enzymes are globular proteins that act as biological catalysts, lowering activation energy. The active site's specific shape binds the substrate, explained by the induced-fit model.
酶是起生物催化剂作用的球状蛋白质，能降低活化能。活性部位的特定形状结合底物，这可用诱导契合模型来解释。
The rate of enzyme-controlled reactions is affected by temperature, pH, enzyme concentration, and substrate concentration. Denaturation at extreme pH or temperature permanently alters the active site.
酶促反应的速率受温度、pH、酶浓度和底物浓度的影响。在极端pH或温度下发生的变性会永久改变活性部位的结构。
Competitive inhibitors resemble the substrate and block the active site, whereas non-competitive inhibitors bind elsewhere and change the active site shape. Both can be reversible or irreversible.
竞争性抑制剂与底物结构相似并阻塞活性部位，而非竞争性抑制剂结合在别处并改变活性部位的形状。两者都可以是可逆或不可逆的。
3. Nucleic Acids: DNA and RNA | 核酸：DNA与RNA
Nucleotides are the monomers of nucleic acids and consist of a phosphate group, a pentose sugar, and a nitrogenous base. In DNA the sugar is deoxyribose; in RNA it is ribose.
核苷酸是核酸的单体，由一个磷酸基团、一个戊糖和一个含氮碱基组成。在DNA中，糖是脱氧核糖；在RNA中，糖是核糖。
DNA's bases are adenine (A), thymine (T), cytosine (C), and guanine (G). RNA uses uracil (U) in place of thymine. Complementary base pairing follows the rule A-T/U and C-G via hydrogen bonds.
DNA的碱基为腺嘌呤(A)、胸腺嘧啶(T)、胞嘧啶(C)和鸟嘌呤(G)。RNA用尿嘧啶(U)替代胸腺嘧啶。互补碱基配对遵循A-T/U和C-G的规则，通过氢键连接。
The DNA double helix consists of two antiparallel strands held together by hydrogen bonds between complementary bases. The sugar-phosphate backbone provides structural stability.
DNA双螺旋由两条反向平行的链组成，链间通过互补碱基之间的氢键连接。糖-磷酸骨架提供了结构稳定性。
DNA replication is semi-conservative: each new DNA molecule contains one original strand and one newly synthesised strand. DNA helicase unwinds the helix, and DNA polymerase adds complementary nucleotides in the 5' to 3' direction.
DNA复制是半保留的：每个新的DNA分子含有一条原始链和一条新合成的链。DNA解旋酶解开双螺旋，DNA聚合酶沿5'到3'方向添加互补核苷酸。
There are three main types of RNA: messenger RNA (mRNA) carries the genetic code from DNA to ribosomes; transfer RNA (tRNA) delivers specific amino acids; ribosomal RNA (rRNA) is a structural component of ribosomes.
RNA主要有三种类型：信使RNA (mRNA) 将遗传密码从DNA带到核糖体；转运RNA (tRNA) 运载特定氨基酸；核糖体RNA (rRNA) 是核糖体的结构组分。
4. Water, ATP, and Inorganic Ions | 水、ATP与无机离子
Water's polarity and ability to form hydrogen bonds give it unique properties: it is an excellent solvent, has a high specific heat capacity, a high latent heat of vaporisation, and strong cohesion. These properties support life as a transport medium, temperature buffer, and coolant.
水分子具有极性并能形成氢键，这赋予了它独特的性质：优良的溶剂、高比热容、高蒸发潜热和强内聚力。这些特性使水能作为运输介质、温度缓冲剂和冷却剂来支持生命活动。
Adenosine triphosphate (ATP) is the universal energy currency. It is composed of adenine, ribose, and three phosphate groups. Hydrolysis of ATP to ADP + Pi (inorganic phosphate) releases energy for cellular work.
三磷酸腺苷(ATP)是通用的能量通货。它由腺嘌呤、核糖和三个磷酸基团组成。ATP水解为ADP和Pi（无机磷酸）会释放能量供细胞活动使用。
Inorganic ions have specific roles: iron(II) ions (Fe²⁺) are a component of haemoglobin; phosphate ions (PO₄³⁻) are needed for ATP and nucleic acids; sodium ions (Na⁺) are involved in co-transport; and hydrogen ions (H⁺) determine pH.
无机离子具有特定作用：亚铁离子(Fe²⁺)是血红蛋白的组分；磷酸根离子(PO₄³⁻)是ATP和核酸所必需的；钠离子(Na⁺)参与协同转运；氢离子(H⁺)决定pH值。
5. Eukaryotic and Prokaryotic Cell Structure | 真核与原核细胞结构
Eukaryotic cells possess a membrane-bound nucleus and organelles such as mitochondria, endoplasmic reticulum, the Golgi apparatus, lysosomes, and (in plants) chloroplasts and a permanent vacuole.
真核细胞具有膜包被的细胞核和细胞器，例如线粒体、内质网、高尔基体、溶酶体，以及（在植物中）叶绿体和中央大液泡。
The nucleus contains chromatin (DNA wrapped around histones) and a nucleolus. Nuclear pores regulate the passage of molecules between the nucleus and cytoplasm.
细胞核含有染色质（DNA缠绕在组蛋白上）和核仁。核孔调控分子在细胞核与细胞质之间的进出。
Prokaryotic cells (bacteria) lack a nucleus; their circular DNA lies free in the cytoplasm. They have smaller (70S) ribosomes, a cell wall made of peptidoglycan, and may possess plasmids, a capsule, and flagella.
原核细胞（细菌）没有细胞核；其环状DNA游离在细胞质中。它们拥有较小的（70S）核糖体、由肽聚糖构成的细胞壁，还可能带有质粒、荚膜和鞭毛。
Viruses are acellular and consist of genetic material (DNA or RNA) enclosed in a protein capsid, sometimes with a lipid envelope. They replicate only inside host cells, so they are not classified as living organisms.
病毒是非细胞结构，由遗传物质（DNA或RNA）包裹在蛋白质衣壳内，有时带有脂质包膜。它们只能在宿主细胞内复制，因此不被归为生物体。
6. Cell Membranes and Transport Mechanisms | 细胞膜与运输机制
The fluid mosaic model describes the cell membrane as a phospholipid bilayer with embedded proteins, cholesterol, and glycoproteins. The phospholipids have hydrophilic heads and hydrophobic tails, forming a selectively permeable barrier.
流动镶嵌模型将细胞膜描述为磷脂双分子层，其中镶嵌有蛋白质、胆固醇和糖蛋白。磷脂具有亲水头部和疏水尾部，形成选择性渗透屏障。
Simple diffusion is the net movement of small, non-polar molecules directly through the bilayer, down a concentration gradient, without the use of energy.
简单扩散是小的非极性分子直接穿过磷脂双分子层，沿浓度梯度净移动，不消耗能量。
Facilitated diffusion uses channel or carrier proteins to transport specific ions or polar molecules down their gradient; it is still passive.
易化扩散利用通道蛋白或载体蛋白，沿浓度梯度运输特定离子或极性分子；它仍属于被动运输。
Osmosis is the net movement of water from a region of higher water potential (less negative) to a region of lower water potential (more negative) through a partially permeable membrane.
渗透作用是水分子通过半透膜，从水势较高（负值较小）的区域向水势较低（负值较大）的区域净移动。
Active transport moves substances against their concentration gradient using energy from ATP and specific carrier proteins (pumps). The sodium–potassium pump is a classic example.
主动运输利用ATP能量和特定载体蛋白（泵），逆浓度梯度移动物质。钠钾泵是经典的例子。
Endocytosis and exocytosis transport large molecules or particles across the membrane by the formation or fusion of vesicles, requiring energy.
内吞和胞吐作用通过形成或融合囊泡来跨膜运输大分子或颗粒，需要消耗能量。
7. The Cell Cycle and Cell Division | 细胞周期与细胞分裂
The cell cycle comprises interphase (G₁, S, G₂) and the mitotic phase (mitosis and cytokinesis). During S phase, DNA replicates to produce sister chromatids held together at the centromere.
细胞周期包括间期（G₁期、S期、G₂期）和分裂期（有丝分裂和胞质分裂）。在S期，DNA复制产生由着丝粒连接在一起的姐妹染色单体。
Mitosis produces two genetically identical diploid daughter cells and is divided into prophase, metaphase, anaphase, and telophase. It is important for growth, repair, and asexual reproduction.
有丝分裂产生两个遗传上相同的二倍体子细胞，分为前期、中期、后期和末期。它对生长、修复和无性繁殖至关重要。
Meiosis produces four genetically varied haploid gametes through two successive divisions. In meiosis I, homologous chromosomes pair up and undergo crossing over, then separate; in meiosis II, sister chromatids separate.
减数分裂通过两次连续分裂产生四个遗传上不同的单倍体配子。在减数第一次分裂中，同源染色体配对并发生交叉互换，然后分离；减数第二次分裂中，姐妹染色单体分开。
Independent segregation of homologous chromosomes and crossing over during prophase I both generate genetic variation among gametes.
同源染色体的独立分配和前期I的交叉互换都会在配子间产生遗传变异。
8. Genetic Information and Variation | 遗传信息与变异
Genes are sequences of DNA bases that code for the amino acid sequence of a polypeptide. The genetic code is a triplet code; each codon (three bases) specifies one amino acid.
基因是编码多肽氨基酸序列的DNA碱基序列。遗传密码是三联体密码；每个密码子（三个碱基）决定一个氨基酸。
Protein synthesis involves transcription and translation. In transcription, one DNA strand is used as a template to synthesise pre-mRNA, which is then spliced to form mature mRNA. Translation occurs on ribosomes, where tRNA anticodons match mRNA codons to assemble a polypeptide chain.
蛋白质合成包括转录和翻译。在转录中，一条DNA链作为模板合成前体mRNA，然后经过剪接形成成熟的mRNA。翻译发生在核糖体上，tRNA的反密码子与mRNA的密码子配对，组装多肽链。
Gene expression can be regulated at the transcriptional level by transcription factors, or post-transcriptionally through mRNA processing and modification.
基因表达可以在转录水平受转录因子调控，或在转录后通过mRNA加工和修饰来调控。
Mutations are changes in the DNA base sequence. Substitution mutations may be silent, mis-sense, or non-sense; insertion or deletion mutations cause frameshifts, altering the entire downstream amino acid sequence.
突变是DNA碱基序列的改变。替换突变可能是沉默、错义或无义突变；插入或缺失突变引起移码，改变下游整个氨基酸序列。
Continuous variation, such as height, is polygenic and influenced by the environment, whereas discontinuous variation, such as blood group, is controlled by a single gene with distinct phenotypes.
连续变异如身高，是多基因遗传并受环境影响；不连续变异如血型，由单一基因控制，具有截然不同的表型。
9. Gas Exchange and Circulatory Systems | 气体交换与循环系统
Efficient gas exchange surfaces have a large surface area, are thin, moist, and have a rich blood supply to maintain steep concentration gradients. Mammalian alveoli exemplify these adaptations.
高效的气体交换表面具有大的表面积、薄、湿润并有丰富的血液供应以维持陡峭的浓度梯度。哺乳动物肺泡体现了这些适应特征。
In bony fish, water flows unidirectionally over the gill filaments, and a countercurrent flow system ensures that blood always meets water with a higher oxygen concentration, maximising oxygen uptake.
在硬骨鱼中，水单向流过鳃丝，逆流交换系统确保血液始终与氧浓度更高的水流相遇，从而最大限度摄取氧气。
Insects ventilate via a tracheal system: air enters through spiracles and flows through tracheae and tracheoles delivering oxygen directly to tissues. Rhythmic body movements assist ventilation.
昆虫通过气管系统换气：空气通过气门进入，流经气管和微气管，直接向组织输送氧气。有节奏的身体运动辅助通风。
The mammalian circulatory system is a closed, double circulation. The heart pumps deoxygenated blood to the lungs (pulmonary circuit) and oxygenated blood to the rest of the body (systemic circuit).
哺乳动物的循环系统是闭管式双循环。心脏将缺氧血泵入肺部（肺循环），将富氧血泵送至全身（体循环）。
Haemoglobin is a quaternary protein with four haem groups, each binding one O₂ molecule. Cooperative binding produces a sigmoidal oxygen dissociation curve. The Bohr effect describes how increased CO₂ (lower pH) shifts the curve to the right, promoting oxygen unloading in respiring tissues.
血红蛋白是一种具有四个血红素基团的四级结构蛋白质，每个可结合一个O₂。协同结合产生S形氧解离曲线。玻尔效应描述了CO₂增加（pH降低）如何使曲线右移，促进氧气在呼吸组织中的释放。
10. Transport in Plants and Immune Defenses | 植物中的运输与免疫防御
Xylem vessels transport water and mineral ions from roots to shoots. The cohesion–tension theory explains how transpiration from leaves pulls water up the continuous column due to the cohesive and adhesive properties of water.
木质部导管将水和矿质离子从根部运输到地上部分。内聚力-张力学说解释了叶片蒸腾作用如何利用水的内聚力和附着力，拉动连续水柱向上运输。
Phloem translocates sucrose (and amino acids) from sources to sinks. The mass-flow hypothesis proposes that active loading of solutes lowers water potential in the phloem at the source, causing water to enter by osmosis and generate a pressure gradient.
韧皮部将蔗糖（和氨基酸）从源运输到库。集流学说认为，源端主动装载溶质降低了韧皮部的水势，导致水通过渗透作用进入，产生压力梯度。
The body's first line of defence includes physical barriers such as skin and mucous membranes. The second, non-specific line includes phagocytosis by neutrophils and macrophages, plus the inflammatory response.
人体的第一道防线包括物理屏障，如皮肤和粘膜。第二道非特异性防线包括中性粒细胞和巨噬细胞的吞噬作用，以及炎症反应。
Specific immune responses involve T lymphocytes (cell-mediated immunity) and B lymphocytes (humoral immunity). Helper T cells activate phagocytes, cytotoxic T cells, and B cells.
特异性免疫应答涉及T淋巴细胞（细胞免疫）和B淋巴细胞（体液免疫）。辅助性T细胞能激活吞噬细胞、细胞毒性T细胞和B细胞。
B cells produce antibodies that are specific to antigens. Clonal selection and expansion generate plasma cells that secrete large quantities of antibody. Memory cells enable a faster, stronger secondary response upon re-exposure to the same pathogen.
B细胞产生针对特定抗原的抗体。克隆选择和增殖产生可分泌大量抗体的浆细胞。记忆细胞使机体在再次接触同一病原体时产生更快、更强的二次应答。
Vaccination introduces antigens in a harmless form, stimulating immunity without causing disease. Herd immunity protects vulnerable individuals when a high percentage of the population is immunised.
疫苗接种以无害形式引入抗原，在不会致病的情况下激发免疫。当人群中免疫比例很高时，群体免疫保护了易感个体。
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