📚 Year 13 SQA Biology: Core Concepts Revision | Year 13 SQA 生物：核心知识点梳理
This article distills the essential core concepts for SQA Advanced Higher Biology, designed for Year 13 students aiming to consolidate their understanding across the three units: Cells and Proteins, Organisms and Evolution, and Investigative Biology. From cell cycle control and protein synthesis to population genetics and experimental statistics, mastering these topics will sharpen your exam performance and scientific thinking.
本文提炼了 SQA Advanced Higher 生物学核心知识点，专为 Year 13 学生梳理三个单元的内容：细胞与蛋白质、生物体与进化以及探究生物学。从细胞周期调控、蛋白质合成到群体遗传学和实验统计，掌握这些关键内容将助你提升考试成绩和科学思维。
1. The Cell Cycle and Checkpoints | 细胞周期与检查点
The eukaryotic cell cycle is divided into interphase (G₁, S, G₂) and mitosis (M phase). During G₁ the cell grows and synthesises proteins; DNA is replicated in S phase; G₂ prepares for division. Mitosis consists of prophase, metaphase, anaphase and telophase, followed by cytokinesis. Orderly progression is enforced by checkpoints at G₁, G₂ and metaphase, where the cell assesses DNA integrity, cell size and chromosome attachment.
真核细胞周期分为间期 (G₁ 期、S 期、G₂ 期) 和分裂期 (M 期)。G₁ 期细胞生长并合成蛋白质；S 期 DNA 复制；G₂ 期为分裂做准备。有丝分裂包括前期、中期、后期和末期，最后胞质分裂。细胞周期在 G₁ 期、G₂ 期和中期设有检查点，评估 DNA 完整性、细胞大小和染色体附着，确保有序推进。
| Checkpoint | Key events | 关键事件 |
|---|---|---|
| G₁ checkpoint | Checks for DNA damage and growth signals; p53 can halt cycle or trigger apoptosis; restriction point controlled by Rb protein | 检查 DNA 损伤与生长信号；p53 可暂停周期或触发凋亡；限制点由 Rb 蛋白控制 |
| G₂ checkpoint | Verifies DNA replication completeness and cell size; CDK1-cyclin B complex triggers mitosis | 确认 DNA 复制完整性和细胞大小；CDK1-cyclin B 复合物启动有丝分裂 |
| Metaphase checkpoint | Ensures all chromosomes are attached to spindle microtubules at kinetochores before anaphase | 确保所有染色体着丝粒与纺锤体微管连接后才进入后期 |
Cyclin-dependent kinases (CDKs) are the engine of the cell cycle. CDK levels remain constant, but their activity depends on binding to specific cyclins whose concentration oscillates. For example, CDK1-cyclin B promotes entry into mitosis by phosphorylating targets such as lamins and histone H1.
周期蛋白依赖性激酶 (CDK) 是细胞周期的引擎。CDK 浓度恒定，但其活性依赖于与浓度周期性波动的特定 cyclin 结合。例如 CDK1-cyclin B 通过磷酸化核纤层蛋白和组蛋白 H1 等靶标，促进细胞进入有丝分裂。
2. Protein Synthesis and Post-Translational Modifications | 蛋白质合成与翻译后修饰
Transcription converts a gene’s DNA sequence into mRNA. RNA polymerase II binds to the promoter with the help of general transcription factors, unwinds the DNA and synthesises pre-mRNA in the 5′→3′ direction. In eukaryotes, the pre-mRNA undergoes 5′ capping, splicing to remove introns, and 3′ polyadenylation before export to the cytoplasm.
转录将基因的 DNA 序列转变为 mRNA。RNA 聚合酶 II 在通用转录因子协助下结合启动子，解开 DNA，沿 5′→3′ 方向合成前体 mRNA。真核细胞中，前体 mRNA 经过 5′ 加帽、剪接去除内含子和 3′ 多聚腺苷酸化后输出至细胞质。
Translation on ribosomes decodes the mRNA into a polypeptide chain. tRNAs charged with amino acids match anticodons to mRNA codons. The ribosome catalyses peptide bond formation, and elongation continues until a stop codon is reached. The newly formed polypeptide folds into its three-dimensional conformation, often assisted by chaperone proteins.
核糖体上的翻译将 mRNA 解码为多肽链。携带氨基酸的 tRNA 通过反密码子与 mRNA 密码子配对。核糖体催化肽键形成，延长过程直至遇到终止密码子。新生多肽链折叠成三维构象，常需要分子伴侣协助。
Post-translational modifications (PTMs) regulate protein function, stability and localisation. Common PTMs include phosphorylation (adding phosphate groups to serine, threonine or tyrosine by kinases), glycosylation (adding carbohydrate chains), ubiquitination (tagging for proteasomal degradation) and proteolytic cleavage (e.g. activation of insulin).
翻译后修饰 (PTM) 调节蛋白质功能、稳定性和定位。常见 PTM 包括磷酸化 (激酶将磷酸基团加到丝氨酸、苏氨酸或酪氨酸上)、糖基化 (添加糖链)、泛素化 (标记蛋白质以便蛋白酶体降解) 和蛋白酶切 (如胰岛素原的激活)。
3. Membrane Proteins and Signal Transduction | 膜蛋白与信号转导
Biological membranes are fluid mosaics containing phospholipids, cholesterol and diverse proteins. Integral membrane proteins span the bilayer, while peripheral proteins are attached to the surface. Key types include channels, carriers, pumps, receptors and enzymes. The asymmetry of membrane proteins is essential for cell-to-cell communication.
生物膜是流动镶嵌结构，含有磷脂、胆固醇和多种蛋白质。整合膜蛋白贯穿脂双层，外周蛋白附着于膜表面。主要类型包括通道蛋白、载体蛋白、泵、受体和酶。膜蛋白的不对称分布对细胞间通讯至关重要。
Cell signalling proceeds through reception, transduction and response. A ligand binds to a receptor, often causing a conformational change. Common receptor families include G-protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs) and ligand-gated ion channels. GPCRs activate G-proteins that exchange GDP for GTP, leading to production of second messengers such as cAMP or IP₃/DAG.
细胞信号传导包括接收、转导和响应三个阶段。配体与受体结合引起构象变化。常见受体家族包括 G 蛋白偶联受体 (GPCR)、受体酪氨酸激酶 (RTK) 和配体门控离子通道。GPCR 激活 G 蛋白，使 GDP 交换为 GTP，进而产生第二信使如 cAMP 或 IP₃/DAG。
Receptor tyrosine kinases dimerise upon ligand binding, autophosphorylate tyrosine residues, and recruit relay proteins that trigger phosphorylation cascades, e.g. the Ras-MAP kinase pathway. Second messengers such as Ca²⁺ ions, cAMP and IP₃ amplify the signal and lead to cellular responses including changes in gene expression, metabolism or cell division.
RTK 与配体结合后二聚化，自磷酸化酪氨酸残基，并招募接头蛋白启动磷酸化级联反应，如 Ras-MAP 激酶通路。Ca²⁺、cAMP 和 IP₃ 等第二信使放大信号并引发细胞响应，包括基因表达变化、代谢调整或细胞分裂。
4. Gene Expression and Epigenetic Regulation | 基因表达与表观遗传调控
Only a fraction of the genome is transcribed at any time. Gene expression is controlled at multiple levels: chromatin structure, transcription initiation, RNA processing, mRNA stability and translation. Transcription factors bind to promoter-proximal elements or distant enhancers/silencers, interacting with mediator complexes to fine-tune RNA polymerase II activity.
基因组中只有一部分随时被转录。基因表达在多层次受控：染色质结构、转录起始、RNA 加工、mRNA 稳定性和翻译。转录因子与启动子近端元件或远端的增强子/沉默子结合，并与中介体复合物相互作用，精准调节 RNA 聚合酶 II 活性。
Epigenetic modifications change gene activity without altering the DNA sequence. DNA methylation typically occurs at CpG dinucleotides and is associated with transcriptional silencing. Histone acetylation, catalysed by histone acetyltransferases (HATs), relaxes chromatin and promotes transcription, while deacetylation by histone deacetylases (HDACs) restores tight packing.
表观遗传修饰在不改变 DNA 序列的情况下调控基因活性。DNA 甲基化通常发生在 CpG 二核苷酸上，与转录沉默相关。组蛋白乙酰化由组蛋白乙酰基转移酶 (HAT) 催化，使染色质松弛、促进转录；而组蛋白去乙酰化酶 (HDAC) 则恢复染色质紧密状态。
Non-coding RNAs, including siRNA and miRNA, can bind to complementary mRNA sequences and trigger degradation or block translation. These RNA interference pathways provide an additional layer of gene regulation and are exploited in research and medicine for gene silencing.
非编码 RNA，包括 siRNA 和 miRNA，与互补的 mRNA 序列结合，引发 mRNA 降解或阻断翻译。这些 RNA 干扰通路提供了额外的基因调控层面，并被用于研究及医学中的基因沉默。
5. Genetic Engineering and Genomics | 基因工程与基因组学
Genetic engineering involves manipulating an organism’s DNA for research, medicine or agriculture. Key tools include restriction endonucleases that cut DNA at specific recognition sites, DNA ligase for joining fragments, and vectors such as plasmids to carry recombinant DNA into host cells. Transformation, transfection or viral transduction can introduce the foreign DNA.
基因工程涉及操纵生物体 DNA，用于研究、医学和农业。关键工具包括在特定识别位点切割 DNA 的限制性内切酶、连接片段的 DNA 连接酶，以及质粒等载体将重组 DNA 导入宿主细胞。通过转化、转染或病毒转导引入外源 DNA。
CRISPR-Cas9 enables precise genome editing. A guide RNA directs the Cas9 nuclease to a target sequence, where it creates a double-strand break. Cellular repair via non-homologous end joining (NHEJ) can disrupt a gene, while homology-directed repair (HDR) can introduce a desired mutation using a donor template.
CRISPR-Cas9 实现精准基因组编辑。向导 RNA 将 Cas9 核酸酶引导至靶序列，造成双链断裂。通过非同源末端连接 (NHEJ) 进行修复可破坏基因，而通过同源定向修复 (HDR) 则可用供体模板引入预期突变。
| PCR step | Description | 描述 |
|---|---|---|
| Denaturation | Heat to ~95°C to separate DNA strands | 加热至约 95°C 使 DNA 双链解开 |
| Annealing | Cool to 50–65°C; primers bind to complementary sequences | 降温至 50–65°C；引物与互补序列结合 |
| Extension | Taq polymerase at ~72°C synthesises new strands; cycle repeated 25–35 times | Taq 聚合酶在约 72°C 合成新链；循环 25–35 次 |
Gel electrophoresis separates DNA fragments by size. DNA loaded into a gel matrix migrates towards the positive electrode; smaller fragments travel faster. Banding patterns are visualised with fluorescent dyes. Sanger sequencing uses chain-terminating ddNTPs to read nucleotide order, while next-generation sequencing technologies allow massive parallel sequencing of entire genomes.
凝胶电泳按大小分离 DNA 片段。将 DNA 加至凝胶基质中，片段向正极移动；较小片段迁移更快。用荧光染料显示条带模式。Sanger 测序利用链终止双脱氧核苷酸 (ddNTP) 读取核苷酸序列，而新一代测序技术可大规模平行测定全基因组。
6. The Immune System and Vaccination | 免疫系统与疫苗接种
The mammalian immune system provides non-specific (innate) and specific (adaptive) defence. Innate defences include physical barriers (skin, mucous), phagocytes (neutrophils, macrophages), natural killer cells and the complement system. The inflammatory response increases blood flow and recruits immune cells to the site of infection.
哺乳动物免疫系统提供非特异性 (先天) 和特异性 (适应性) 防御。先天防御包括物理屏障 (皮肤、黏膜)、吞噬细胞 (中性粒细胞、巨噬细胞)、自然杀伤细胞和补体系统。炎症反应增加血流，招募免疫细胞至感染部位。
Adaptive immunity relies on lymphocytes. B lymphocytes mature in bone marrow and produce antibodies; T lymphocytes mature in the thymus and differentiate into helper T cells (CD4⁺) and cytotoxic T cells (CD8⁺). Clonal selection ensures that only lymphocytes with receptors matching an antigen proliferate, generating effector and memory cells for long-term immunity.
适应性免疫依赖淋巴细胞。B 淋巴细胞在骨髓成熟并产生抗体；T 淋巴细胞在胸腺成熟，分化为辅助 T 细胞 (CD4⁺) 和细胞毒性 T 细胞 (CD8⁺)。克隆选择确保只有具备匹配抗原受体的淋巴细胞增殖，产生效应细胞和记忆细胞，建立长期免疫。
Antibodies are Y-shaped glycoproteins composed of two heavy and two light chains. The variable region binds a specific antigen, while the constant region can activate complement or bind to phagocytes. Monoclonal antibodies are produced from hybridoma cells and are used in diagnostics (e.g. ELISA) and therapeutics. Vaccination introduces a harmless form of the antigen to stimulate active immunity and memory cell production, providing herd protection.
抗体是由两条重链和两条轻链组成的 Y 形糖蛋白。可变区结合特定抗原，恒定区可激活补体或结合吞噬细胞。单克隆抗体由杂交瘤细胞产生，用于诊断 (如 ELISA) 和治疗。疫苗接种引入无害抗原，诱发主动免疫并产生记忆细胞，从而提供群体保护。
7. Cellular Respiration | 细胞呼吸
Respiration harvests energy from glucose in a series of controlled oxidation steps. Glycolysis occurs in the cytosol, splitting glucose (6C) into two pyruvate molecules (3C) with a net gain of 2 ATP and 2 NADH.
Published by TutorHao | Year 13 Biology Revision Series | aleveler.com
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