📚 GCSE OCR Biology: End-of-Term Revision Guide | GCSE OCR 生物：期末复习提纲
As you approach the end of term, this revision guide consolidates the key topics from the GCSE OCR Biology specification, helping you focus on what matters most for your assessments. Refresh your understanding of cell biology, organisation, bioenergetics, homeostasis, inheritance and ecology.
随着学期接近尾声，这份复习提纲汇总了 GCSE OCR 生物的核心课题，帮助你聚焦考试重点。重温细胞生物学、机体构成、生物能量学、稳态、遗传和生态等内容，为评估做好准备。
1. Cell Structure | 细胞结构
Eukaryotic cells (plant and animal) contain membrane-bound organelles such as the nucleus, mitochondria, ribosomes and, in plants, chloroplasts and a permanent vacuole.
真核细胞（植物和动物）含有膜包被的细胞器，如细胞核、线粒体、核糖体，植物细胞还有叶绿体和中央大液泡。
Prokaryotic cells (bacteria) are much smaller, lack a nucleus, and have a single circular chromosome, plasmid DNA, a cell wall and sometimes flagella.
原核细胞（细菌）小得多，没有细胞核，具有单环状染色体、质粒 DNA、细胞壁，部分有鞭毛。
Microscopy technique: light microscopes allow viewing of living cells at low magnification; electron microscopes have much higher resolution and reveal ultrastructure.
显微镜技术：光学显微镜可观察活细胞，放大倍数较低；电子显微镜分辨率高得多，能显示亚细胞结构。
2. Cell Division | 细胞分裂
Mitosis produces two genetically identical daughter cells for growth and repair. The cell cycle includes interphase (DNA replication), mitosis and cytokinesis.
有丝分裂产生两个遗传上完全相同的子细胞，用于生长和修复。细胞周期包括间期（DNA 复制）、有丝分裂和胞质分裂。
Meiosis occurs in reproductive organs to produce gametes with half the chromosome number (haploid). It introduces genetic variation through crossing over and independent assortment.
减数分裂发生在生殖器官，产生染色体数目减半的配子（单倍体）。通过交叉互换和自由组合引入遗传变异。
In mitosis, chromosome number remains diploid (2n) and daughter cells are identical; in meiosis, chromosome number halves to haploid (n) and cells are genetically varied.
在有丝分裂中，染色体数保持二倍体（2n），子细胞相同；在减数分裂中，染色体数减半为单倍体（n），细胞遗传多样。
3. Organisation in Animals and Plants | 动植物组织层次
Cells are organised into tissues, tissues into organs, and organs into organ systems. Examples include the digestive system, circulatory system, and plant transport system.
细胞构成组织，组织构成器官，器官构成器官系统。例如消化系统、循环系统和植物输导系统。
Animal tissues: muscular, nervous, epithelial and connective tissues. Plant tissues: epidermal, palisade mesophyll, spongy mesophyll, xylem and phloem.
动物组织：肌肉组织、神经组织、上皮组织和结缔组织。植物组织：表皮组织、栅栏组织、海绵组织、木质部和韧皮部。
The leaf is an organ; its tissues are adapted for photosynthesis: palisade cells have many chloroplasts, stomata allow gas exchange, xylem brings water.
叶是一个器官；其组织适应光合作用：栅栏细胞含许多叶绿体，气孔进行气体交换，木质部输送水分。
4. Enzymes | 酶
Enzymes are biological catalysts that speed up chemical reactions without being used up. They have an active site with a specific shape complementary to the substrate.
酶是生物催化剂，能加速化学反应而自身不被消耗。其活性位点具有与底物互补的特定形状。
The lock-and-key model describes how the substrate fits into the active site. Factors affecting enzyme activity include temperature, pH and substrate concentration.
锁钥模型描述底物如何嵌入活性位点。影响酶活性的因素包括温度、pH 和底物浓度。
High temperatures or extreme pH denature the enzyme by breaking bonds that maintain its tertiary structure, permanently changing the active site shape.
高温或极端 pH 会使酶变性，破坏维持其三级结构的键，永久改变活性位点形状。
Digestive enzymes: amylase breaks down starch into maltose; protease breaks down protein into amino acids; lipase breaks down lipids into glycerol and fatty acids.
消化酶：淀粉酶分解淀粉为麦芽糖；蛋白酶分解蛋白质为氨基酸；脂肪酶分解脂质为甘油和脂肪酸。
5. Photosynthesis and Respiration | 光合作用与呼吸作用
Photosynthesis is the process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (light energy).
光合作用是植物利用光能将二氧化碳和水转化为葡萄糖和氧气的过程：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂（光能）。
Limiting factors: light intensity, CO₂ concentration and temperature. The rate is limited by the factor in shortest supply.
限制因素：光照强度、CO₂ 浓度和温度。光合速率受最缺乏的那个因素限制。
Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP). Anaerobic respiration in animals produces lactic acid; in plants and yeast, ethanol and CO₂.
有氧呼吸：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O（+ ATP）。动物无氧呼吸产生乳酸；植物和酵母无氧呼吸产生乙醇和 CO₂。
Metabolism includes all chemical reactions, with respiration providing energy for many processes (e.g., active transport, muscle contraction).
新陈代谢包括所有化学反应，呼吸作用为许多过程提供能量（如主动运输、肌肉收缩）。
6. The Digestive System | 消化系统
The digestive system breaks down large insoluble food molecules into small soluble molecules for absorption. Organs: mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine, rectum and anus. Accessory organs: salivary glands, liver, gallbladder and pancreas.
消化系统将大块不溶性食物分子分解为小的可溶性分子以便吸收。器官：口腔、食管、胃、小肠（十二指肠和回肠）、大肠、直肠和肛门。辅助器官：唾液腺、肝、胆囊和胰腺。
Digestion of carbohydrates begins in the mouth with amylase; proteins are digested in the stomach by pepsin; lipids are emulsified by bile and digested by lipase in the small intestine.
碳水化合物的消化始于口腔中的淀粉酶；蛋白质在胃中被胃蛋白酶消化；脂质被胆汁乳化并在小肠中被脂肪酶消化。
The small intestine is adapted for absorption: large surface area (villi and microvilli), thin epithelium, rich blood supply and lacteal for fatty acid absorption.
小肠适于吸收：巨大的表面积（绒毛和微绒毛）、薄上皮、丰富的血液供应以及用于吸收脂肪酸的乳糜管。
7. The Circulatory System | 循环系统
The human circulatory system consists of the heart, blood vessels and blood. It is a double circulatory system: pulmonary circulation to the lungs, systemic circulation to the body.
人体循环系统由心脏、血管和血液组成。是双循环系统：肺循环至肺，体循环至全身。
The heart has four chambers: left and right atria, left and right ventricles. The left ventricle has thicker muscle wall to pump blood around the body at high pressure.
心脏有四个腔室：左、右心房和左、右心室。左心室肌肉壁较厚，以高压将血液泵往全身。
Arteries carry blood away from the heart, have thick muscular walls; veins carry blood to the heart, contain valves; capillaries are thin-walled for exchange.
动脉将血液从心脏运出，管壁厚实有弹性；静脉将血液送回心脏，含有瓣膜；毛细血管壁薄，利于物质交换。
Blood components: red blood cells (haemoglobin, transport O₂), white blood cells (defence), platelets (clotting), plasma (transports CO₂, hormones, nutrients).
血液成分：红细胞（含血红蛋白，运输 O₂）、白细胞（防御）、血小板（凝血）、血浆（运输 CO₂、激素、营养物质等）。
8. Health and Disease | 健康与疾病
Health is a state of physical, mental and social well-being. Communicable diseases are caused by pathogens (bacteria, viruses, fungi, protists) and can be spread; non-communicable diseases are not infectious.
健康是身体、心理和社会的完好状态。传染病由病原体（细菌、病毒、真菌、原生生物）引起并可传播；非传染性疾病无传染性。
Body defence: skin, nose hairs, mucus, stomach acid, and the immune system (phagocytes engulf pathogens; lymphocytes produce antibodies). Vaccination trains the immune system.
身体防御：皮肤、鼻毛、黏液、胃酸，以及免疫系统（吞噬细胞吞噬病原体；淋巴细胞产生抗体）。疫苗接种可训练免疫系统。
Drugs: antibiotics kill bacteria but not viruses. Painkillers relieve symptoms but do not kill pathogens. Development of antibiotic resistance is a major concern.
药物：抗生素杀死细菌却对病毒无效。止痛药缓解症状但不杀灭病原体。抗生素耐药性的产生令人担忧。
Cardiovascular disease: risk factors include smoking, high-fat diet, lack of exercise. Stents and statins are treatments.
心血管疾病：风险因素包括吸烟、高脂饮食、缺乏运动。可使用支架和他汀类药物治疗。
9. Nervous System and Hormones | 神经系统与激素
The nervous system uses electrical impulses for rapid, short-lived responses. A reflex arc involves receptor → sensory neurone → relay neurone → motor neurone → effector.
神经系统利用电信号实现快速、短暂的反应。反射弧包括感受器→感觉神经元→中间神经元→运动神经元→效应器。
Hormones are chemical messengers released into the blood, producing slower but longer-lasting effects. Key hormones: insulin (lowers blood glucose), glucagon (raises it), adrenaline (fight or flight).
激素是分泌入血液的化学信使，作用慢但持久。关键激素：胰岛素（降低血糖）、胰高血糖素（升高血糖）、肾上腺素（应激反应）。
Endocrine glands: pituitary (master gland), thyroid, pancreas, ovaries, testes and adrenal glands. Negative feedback maintains homeostasis (e.g., blood glucose regulation).
内分泌腺：垂体（主腺）、甲状腺、胰腺、卵巢、睾丸和肾上腺。负反馈维持稳态（如血糖调节）。
10. Homeostasis | 稳态
Homeostasis is the maintenance of a constant internal environment. Key examples: thermoregulation (skin, hypothalamus), osmoregulation (kidneys, ADH) and blood glucose control.
稳态是指维持恒定的内环境。关键实例：体温调节
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