📚 GCSE Edexcel Biology: Last-Minute Revision Notes | GCSE Edexcel 生物：考前冲刺笔记
Last-minute revision can be stressful, but focusing on key concepts and exam techniques will help you succeed. This guide summarises the essential GCSE Edexcel Biology topics, from cell biology to ecosystems, with clear explanations and bilingual support. Use these notes to consolidate your knowledge and tackle those tricky exam questions with confidence.
考前冲刺可能令人紧张，但专注于关键概念和考试技巧将助你取得成功。这份指南总结了GCSE Edexcel生物必考的核心主题，从细胞生物学到生态系统，配有清晰的解释与中英双语支持。利用这些笔记巩固知识，自信地应对棘手的考题。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are made of cells. Eukaryotic cells (in animals, plants, fungi, and protists) have a nucleus containing genetic material, while prokaryotic cells (bacteria) have a single loop of DNA floating freely in the cytoplasm and no membrane-bound organelles.
所有生物都由细胞构成。真核细胞（存在于动物、植物、真菌和原生生物）具有含有遗传物质的细胞核，而原核细胞（细菌）只有一条裸露的DNA在细胞质中游离，没有膜结合的细胞器。
| Feature (特征) | Animal Cell (动物细胞) | Plant Cell (植物细胞) | Bacterial Cell (细菌细胞) |
|---|---|---|---|
| Nucleus (细胞核) | Yes | Yes | No |
| Cell Wall (细胞壁) | No | Yes, made of cellulose | Yes, made of peptidoglycan |
| Chloroplasts (叶绿体) | No | Yes | No |
| Plasmid DNA (质粒DNA) | No | No | Often present |
Specialised cells have adaptations to carry out specific functions. Sperm cells contain many mitochondria for energy and a streamlined head to penetrate the egg. Root hair cells have a large surface area to absorb water and minerals efficiently.
特化的细胞具有适应其特定功能的结构。精子细胞含有很多线粒体提供能量，并具有锥形头部便于穿透卵子。根毛细胞具有很大的表面积以高效吸收水分和矿物质。
Magnification is calculated using the formula: Magnification = size of image / actual size of object. Always convert measurements the same unit before calculation (1 mm = 1000 µm, 1 µm = 1000 nm).
放大倍数计算公式为：放大倍数 = 图像大小 / 实物实际大小。计算前务必将所有量度转换为相同单位（1 毫米 = 1000 微米，1 微米 = 1000 纳米）。
2. Enzymes and Biological Reactions | 酶与生物反应
Enzymes are protein molecules that act as biological catalysts, speeding up metabolic reactions without being changed or used up. Each enzyme has an active site with a shape complementary to its substrate – the lock-and-key model explains this specificity.
酶是起生物催化剂作用的蛋白质分子，能够加速代谢反应而不被改变或消耗。每种酶都有一个与底物形状互补的活性位点——锁钥模型可以解释这种专一性。
Enzyme activity is affected by temperature and pH. As temperature rises, activity increases until an optimum is reached; beyond this, the enzyme denatures, and the active site shape is permanently altered. Similarly, each enzyme works best at a specific pH.
酶的活性受温度和pH影响。随温度升高，活性增加直至最适温度；超过此温度酶会变性，活性位点形状被永久改变。同样地，每种酶都有最适pH值。
Key digestive enzymes: amylase (produced in salivary glands and pancreas) breaks starch into maltose; protease (stomach, pancreas) breaks proteins into amino acids; lipase (pancreas) breaks lipids into fatty acids and glycerol. Bile emulsifies fats but is not an enzyme.
关键消化酶：淀粉酶（由唾液腺和胰腺分泌）将淀粉分解为麦芽糖；蛋白酶（胃、胰腺）将蛋白质分解为氨基酸；脂肪酶（胰腺）将脂肪分解为脂肪酸和甘油。胆汁能乳化脂肪，但不是酶。
3. Cell Division and Genetics | 细胞分裂与遗传学
Mitosis produces two genetically identical diploid daughter cells, used for growth, repair, and asexual reproduction. The cell cycle includes interphase (DNA replication) and mitosis (prophase, metaphase, anaphase, telophase – remember PMAT), followed by cytokinesis.
有丝分裂产生两个遗传上相同的二倍体子细胞，用于生长、修复和无性生殖。细胞周期包括间期（DNA复制）和有丝分裂（前期、中期、后期、末期——记住PMAT），随后是胞质分裂。
Meiosis produces four genetically varied haploid gametes (sperm or egg). It involves two divisions; in the first division, homologous chromosomes pair up and crossing over occurs, leading to new combinations of alleles and increasing genetic diversity.
减数分裂产生四个遗传上不同的单倍体配子（精子或卵子）。该过程包含两次分裂；在第一次分裂中，同源染色体配对并发生交叉，由此产生新的等位基因组合，增加遗传多样性。
Monohybrid inheritance can be shown using a Punnett square. For example, crossing two heterozygous individuals (Aa × Aa) produces offspring with genotype ratio 1 AA : 2 Aa : 1 aa and, if A is dominant, phenotype ratio 3 dominant : 1 recessive.
单基因遗传可以用庞纳特方格表示。例如，两个杂合个体（Aa × Aa）杂交，后代的基因型比例为 1 AA : 2 Aa : 1 aa，若 A 为显性，表型比例为 3 显性 : 1 隐性。
| A | a | |
| A | AA | Aa |
| a | Aa | aa |
Some disorders are inherited: cystic fibrosis is caused by a recessive allele, so sufferers must inherit two copies. Huntington’s disease is caused by a dominant allele, meaning only one copy is needed to develop the condition.
某些疾病是遗传的：囊性纤维化由隐性等位基因引起，患者必须遗传到两个拷贝。亨廷顿舞蹈症由显性等位基因引起，只需一个拷贝即可患病。
4. DNA and Protein Synthesis | DNA与蛋白质合成
DNA is a polymer made of two strands forming a double helix. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a base (adenine, thymine, cytosine, guanine). Complementary base pairing holds the strands together: A pairs with T, C pairs with G.
DNA是由两条链组成的双螺旋聚合物。每个核苷酸包含一个脱氧核糖、一个磷酸基团和一个含氮碱基（腺嘌呤、胸腺嘧啶、胞嘧啶、鸟嘌呤）。互补碱基配对将两条链维系在一起：A与T配对，C与G配对。
Protein synthesis occurs in two stages. Transcription: a gene’s DNA is used as a template to make mRNA, which carries the code out of the nucleus. Translation: at a ribosome, tRNA molecules bring specific amino acids matching the mRNA codons, linking them to form a polypeptide.
蛋白质合成分两个阶段。转录：以基因的DNA为模板制造mRNA，mRNA携带遗传密码离开细胞核。翻译：在核糖体上，tRNA携带与mRNA密码子对应的特定氨基酸，将它们连接起来形成多肽链。
Mutations are changes in the DNA sequence. A substitution may change just one amino acid (or none, due to degeneracy), while an insertion or deletion can cause a frameshift, altering every amino acid after the mutation, often producing a non-functional protein.
突变是DNA序列的改变。替换可能只改变一个氨基酸（或由于简并性而不改变），而插入或缺失可导致移码突变，改变突变之后的所有氨基酸，常产生无功能的蛋白质。
5. Natural Selection and Evolution | 自然选择与进化
Charles Darwin proposed the theory of evolution by natural selection. Individuals with characteristics better suited to their environment are more likely to survive, reproduce, and pass on the advantageous alleles. Over many generations, these alleles become more common.
查尔斯·达尔文提出了自然选择进化论。具有更适应环境特征的个体更可能存活、繁衍并将有利等位基因传递给后代。经过很多代，这些等位基因在种群中变得更加普遍。
Antibiotic resistance in bacteria is a clear example of natural selection. Random mutations can produce resistance; when antibiotics are used, non-resistant bacteria die, but resistant ones survive and multiply, passing the resistance gene to their offspring.
细菌的抗生素耐药性是自然选择的明显实例。随机突变可产生耐药性；当使用抗生素时，非耐药细菌死亡，而耐药细菌存活并大量繁殖，将耐药基因传递给子代。
Fossils provide evidence for evolution. They show how species have changed over time, and the fossil record documents increased complexity over geological eras. Evidence also comes from DNA analysis and comparing the anatomy of different species.
化石为进化提供了证据。它们展示了物种如何随时间变化，化石记录记录了各地质年代生物复杂性的增加。证据还来自DNA分析及比较不同物种的解剖结构。
6. Health and Disease | 健康与疾病
Pathogens cause communicable diseases. Viruses (e.g., measles, HIV) invade host cells and reproduce inside them. Bacteria (e.g., Salmonella, tuberculosis) release toxins. Fungi and protists (e.g., rose black spot, malaria) also cause disease. The body’s first line of defence includes skin, mucus, and stomach acid.
病原体引起传染性疾病。病毒（如麻疹、HIV）侵入宿主细胞并在其内部繁殖。细菌（如沙门氏菌、肺结核）释放毒素。真菌和原生生物（
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