📚 GCSE OCR Biology: Biotechnology Key Points | GCSE OCR 生物：生物技术 考点精讲
Biotechnology harnesses living organisms and biological systems to create useful products. In GCSE OCR Biology, you need to understand both traditional techniques like fermentation and modern methods such as genetic engineering and cloning, including their applications, benefits, and ethical considerations.
生物技术利用生物体和生物系统来制造有用的产品。在 GCSE OCR 生物学中，你需要理解传统技术（如发酵）和现代方法（如基因工程和克隆），包括它们的应用、益处和伦理考量。
1. What is Biotechnology? | 什么是生物技术？
Biotechnology is the use of living organisms (such as bacteria, yeast, fungi, and plants) or their enzymes to make products for human use. It spans from ancient practices like bread-making to cutting-edge gene therapy.
生物技术是利用生物体（如细菌、酵母、真菌和植物）或其酶来制造供人类使用的产品。它涵盖了从古代实践（如制作面包）到前沿的基因疗法。
There are two main branches: traditional biotechnology, which relies on natural processes like fermentation, and modern biotechnology, which involves genetic modification and cloning.
主要分为两个分支：传统生物技术，依赖于发酵等自然过程；以及现代生物技术，涉及基因改造和克隆。
2. Traditional Biotechnology: Fermentation Basics | 传统生物技术：发酵基础
Fermentation is a metabolic process where microorganisms convert sugars into acids, gases, or alcohol in the absence of oxygen (anaerobic respiration). The key equation for yeast fermentation is:
发酵是一种代谢过程，微生物在缺氧（厌氧呼吸）条件下将糖类转化为酸、气体或酒精。酵母发酵的关键方程式为：
Glucose → Ethanol + Carbon dioxide (+ energy)
葡萄糖 → 乙醇 + 二氧化碳（+ 能量）
This process is exploited to make bread, alcoholic drinks, and biofuels. For yoghurt and cheese, bacteria carry out lactic acid fermentation:
这一过程被用于制作面包、酒精饮料和生物燃料。制作酸奶和奶酪时，细菌进行乳酸发酵：
Glucose → Lactic acid (+ energy)
葡萄糖 → 乳酸（+ 能量）
3. Making Yoghurt and Cheese | 制作酸奶和奶酪
Yoghurt production involves two species of bacteria: Lactobacillus bulgaricus and Streptococcus thermophilus. They ferment lactose (milk sugar) into lactic acid, which lowers the pH and causes milk proteins (casein) to coagulate, thickening the milk into yoghurt. The acidic environment also prevents the growth of harmful pathogens, acting as a natural preservative.
酸奶生产涉及两种细菌：保加利亚乳杆菌和嗜热链球菌。它们将乳糖（牛奶中的糖）发酵成乳酸，降低 pH 值，使牛奶蛋白（酪蛋白）凝固，牛奶因此变稠成为酸奶。酸性环境还能抑制有害病原体的生长，起到天然防腐剂的作用。
Cheese making uses similar bacterial fermentation but adds rennet (an enzyme) to separate curds (solid casein) from whey (liquid). The curds are pressed and ripened by other microbes to develop flavours.
奶酪制作使用类似的细菌发酵，但会加入凝乳酶（一种酶）来分离凝乳（固体酪蛋白）和乳清（液体）。凝乳经压榨后由其他微生物熟化，从而形成独特的风味。
4. Bread Making | 面包制作
Bread dough is mixed with yeast (Saccharomyces cerevisiae). The yeast ferments the sugars released from starch by the enzyme amylase, producing carbon dioxide and ethanol. The CO₂ bubbles get trapped in the gluten network of the dough, causing it to rise and giving bread a light, spongy texture. Ethanol evaporates during baking.
面包面团中加入酵母（酿酒酵母）。酵母发酵由淀粉酶从淀粉中释放出的糖类，产生二氧化碳和乙醇。二氧化碳气泡被困在面团的麸质网络中，使其膨胀，赋予面包轻盈、多孔的结构。乙醇在烘烤过程中蒸发。
Optimum conditions for yeast activity are warm temperatures (around 30–35 °C) and moisture. Too high a temperature will denature the enzymes and kill the yeast.
酵母活动的最佳条件是温暖的环境（约 30–35 °C）和水分。温度过高会使酶变性并杀死酵母。
5. Alcoholic Beverages and Biofuels | 酒精饮料与生物燃料
Alcoholic drinks such as beer and wine are produced by yeast fermentation. In beer, barley grains are malted (allowed to germinate) to activate amylase, which breaks starch into maltose. Yeast then ferments maltose into ethanol and CO₂. In wine, naturally occurring sugars from grapes are fermented.
啤酒和葡萄酒等酒精饮料通过酵母发酵生产。在啤酒中，大麦发芽（让其发芽）以激活淀粉酶，将淀粉分解为麦芽糖。然后酵母将麦芽糖发酵为乙醇和二氧化碳。在葡萄酒中，葡萄中天然存在的糖类被发酵。
Biofuels like bioethanol are produced on an industrial scale using yeast to ferment sugar cane or corn starch. The ethanol is distilled and used as a renewable fuel, reducing reliance on fossil fuels. However, large-scale production raises concerns about land use for food crops versus fuel.
生物燃料（如生物乙醇）在工业规模上使用酵母发酵甘蔗或玉米淀粉进行生产。乙醇经过蒸馏，用作可再生燃料，减少对化石燃料的依赖。然而，大规模生产引发了关于粮食作物与燃料争夺土地的担忧。
6. Industrial Fermenters | 工业发酵罐
Large-scale production of enzymes, antibiotics, or biofuels uses industrial fermenters. These vessels are designed to provide optimal conditions for microorganism growth:
酶、抗生素或生物燃料的大规模生产使用工业发酵罐。这些容器旨在为微生物生长提供最佳条件：
- Temperature control: A water jacket circulates warm or cool water to maintain the optimum temperature for enzyme action.
- 温度控制：水套循环温水或冷水，以保持酶作用的最佳温度。
- pH probes and control: Acids or alkalis are added to maintain the ideal pH.
- pH 探头与控制：添加酸或碱以维持理想的 pH 值。
- Nutrient supply: A sterile nutrient medium is provided; glucose or other sugars are often fed continuously.
- 营养供应：提供无菌营养培养基；葡萄糖或其他糖类通常连续供给。
- Oxygen supply: Sterile air is pumped in if aerobic respiration is needed; for anaerobic fermentation, oxygen must be excluded.
- 氧气供应：如需有氧呼吸，则泵入无菌空气；对于厌氧发酵，必须排除氧气。
- Aseptic technique: The fermenter is sterilised before use to prevent contamination by unwanted microorganisms that could compete for nutrients or produce toxins.
- 无菌技术：发酵罐在使用前需灭菌，以防止杂菌污染，因为它们会竞争养分或产生毒素。
- Stirring paddles: Keep the contents evenly mixed and help maintain uniform temperature and gas exchange.
- 搅拌桨：使内容物均匀混合，有助于维持均匀的温度和气体交换。
7. Modern Biotechnology: Genetic Engineering | 现代生物技术：基因工程
Genetic engineering involves modifying the genome of an organism by introducing a gene from another organism to give it a desirable characteristic. The organism is then said to be genetically modified (GM) or transgenic.
基因工程涉及通过引入另一个生物的基因来修改生物的基因组，使其获得理想的特性。这样的生物被称为基因改造生物（GM）或转基因生物。
Key tools include restriction enzymes, which cut DNA at specific sequences to leave 'sticky ends', and ligase enzymes, which join the fragments together. Vectors, usually plasmids (small circles of DNA from bacteria), are used to carry the target gene into the host cell.
关键工具包括限制酶，它能识别特定序列切割DNA，留下“黏性末端”；以及连接酶，将DNA片段连接起来。载体通常是质粒（来自细菌的小型环状DNA），用于将目的基因导入宿主细胞。
| Enzyme / Tool | 酶 / 工具 | Function | 功能 |
|---|---|---|---|
| Restriction enzyme | 限制酶 | Cuts DNA at specific base sequences to isolate the desired gene and open the plasmid | 在特定碱基序列处切割DNA，分离所需基因并切开质粒 |
| Ligase | 连接酶 | Joins the sticky ends of the target gene and the plasmid together to form recombinant DNA | 将目的基因的黏性末端与质粒的黏性末端连接，形成重组DNA |
| Plasmid vector | 质粒载体 | Carries the recombinant DNA into the host cell (often a bacterium) | 将重组DNA带入宿主细胞（通常是细菌） |
| Marker gene | 标记基因 | Often inserted alongside the target gene to identify successful uptake (e.g., antibiotic resistance) | 常与目的基因一同插入，用于识别是否成功转入（例如抗生素抗性基因） |
8. Steps in Genetic Engineering (Insulin Example) | 基因工程步骤（以胰岛素为例）
Producing human insulin via genetic engineering is a classic example. The steps are:
通过基因工程生产人胰岛素是一个经典范例。步骤如下：
- Isolate the human insulin gene: Use a restriction enzyme to cut the insulin gene out of human DNA, leaving sticky ends.
- 分离人胰岛素基因：使用限制酶从人类DNA中切下胰岛素基因，留下黏性末端。
- Prepare the plasmid: Cut open a bacterial plasmid with the same restriction enzyme to create complementary sticky ends.
- 准备质粒：用相同的限制酶切开细菌质粒，产生互补的黏性末端。
- Ligation: Mix the insulin gene and the cut plasmid with DNA ligase, which seals the gene into the plasmid, forming recombinant DNA.
- 连接：将胰岛素基因和切开的质粒与DNA连接酶混合，连接酶将基因封入质粒，形成重组DNA。
- Transformation: Insert the recombinant plasmid into a host bacterium, often E. coli. The bacteria are then grown in a fermenter.
- 转化：将重组质粒导入宿主细菌（通常是大肠杆菌）。然后将细菌在发酵罐中培养。
- Selection: Use marker genes (e.g., antibiotic resistance) to identify bacteria that have taken up the plasmid. Those that survive on agar containing an antibiotic have picked up both the resistance marker and the insulin gene.
- 筛选：使用标记基因（如抗生素抗性）来识别已摄取质粒的细菌。那些在含抗生素的琼脂上存活的细菌同时获得了抗性标记和胰岛素基因。
- Production and purification: The bacteria multiply, produce human insulin, which is then extracted and purified for medical use.
- 生产与纯化：细菌大量繁殖，产生人胰岛素，然后提取并纯化，用于医疗。
This method has advantages over the older practice of extracting insulin from animal pancreases: human insulin is less likely to cause allergic reactions, is free from animal pathogens, and can be produced in large quantities.
这种方法优于过去从动物胰腺提取胰岛素的做法：人胰岛素较少引起过敏反应，不含动物病原体，并且可以大量生产。
9. Genetically Modified (GM) Crops | 转基因作物
Crops can be genetically engineered to express traits that improve yield, nutritional content, or resistance to pests, diseases, and herbicides. Common examples include:
农作物可以通过基因工程来表达提高产量、营养成分或增强对病虫害和除草剂抗性的性状。常见示例包括：
- Bt crops: Carry a gene from the bacterium Bacillus thuringiensis that produces a toxin lethal to insect pests, reducing the need for chemical pesticides.
- 抗虫作物（Bt 作物）：携带来自苏云金芽孢杆菌的基因，产生对害虫致命的毒素，减少化学杀虫剂的使用。
- Herbicide-resistant crops: Engineered to survive application of specific herbicides (e.g., glyphosate), allowing farmers to control weeds without harming the crop.
- 抗除草剂作物：经工程改造后可耐受特定除草剂（如草甘膦），农民可在不伤害作物的前提下除草。
- Golden Rice: Modified to produce beta-carotene (provitamin A) to address vitamin A deficiency in developing countries.
- 黄金大米：经改造后可产生β-胡萝卜素（维生素A原），以解决发展中国家的维生素A缺乏问题。
Benefits include higher productivity, enhanced nutritional value, and lower pesticide use. Concerns involve potential allergenicity, impact on wild species (gene flow), and corporate control of seed supplies.
益处包括提高生产力、增强营养价值以及减少农药使用。担忧包括潜在的致敏性、对野生物种的影响（基因漂移）以及企业对种子供应的控制。
10. Cloning: Tissue Culture (Plant Cloning) | 克隆：组织培养（植物克隆）
Cloning produces genetically identical copies of an organism. In plants, micropropagation (tissue culture) is widely used to mass-produce desirable varieties. Steps:
克隆产生遗传上完全相同的生物副本。在植物中，微体繁殖（组织培养）被广泛用于大规模生产理想的品种。步骤：
- Take small pieces of tissue (explants) from a parent plant, ideally from the shoot tip (meristem) because it is virus-free and rapidly dividing.
- 从亲本植物上取一小块组织（外植体），最好取自茎尖（分生组织），因为它无病毒且分裂迅速。
- Surface-sterilise the explants to kill any microbes.
- 对外植体进行表面灭菌，以杀死任何微生物。
- Place the explants on a sterile agar growth medium containing nutrients, plant hormones (auxins and cytokinins) to stimulate cell division and root/shoot development.
- 将外植体放置在含有营养物质和植物激素（生长素和细胞分裂素）的无菌琼脂培养基上，以刺激细胞分裂和根/芽发育。
- Grow in controlled conditions (light, temperature, humidity) until plantlets form, then transfer to soil.
- 在受控条件（光照、温度、湿度）下生长，直到形成小植株，然后移入土壤。
Advantages: rapid propagation of many plants with identical characteristics, can be done year-round, saves rare species, and produces disease-free plants if meristem tissue is used.
优点：快速繁殖大量特性相同的植株，可全年进行，拯救稀有物种，并使用分生组织可生产无病植株。
11. Animal Cloning: Embryo Transplants and Adult Cell Cloning | 动物克隆：胚胎移植与成体细胞克隆
In livestock, embryo transplants allow high-yielding females to produce more offspring. A superior female is treated with hormones to produce many eggs (superovulation). The eggs are fertilised by sperm from a desirable male either naturally or via artificial insemination. The developing embryos are flushed from the uterus and implanted into surrogate mothers. All offspring share the superior parents' genes but are not fully identical unless split earlier.
在家畜中，胚胎移植使高产雌性能产生更多后代。对优质雌性使用激素处理以产生多个卵子（超数排卵）。这些卵子通过自然交配或人工授精与理想雄性的精子受精。发育中的胚胎从子宫中冲出，植入到代孕母亲体内。所有后代都共享优良父母的基因，但除非在早期分裂，否则并不完全一致。
Adult cell cloning (somatic cell nuclear transfer) was made famous by Dolly the sheep. The process:
- Remove the nucleus from an unfertilised egg cell (enucleation).
- 从一个未受精的卵细胞中移除细胞核（去核）。
- Take a diploid nucleus from a body cell (e.g., skin or udder cell) of the adult animal to be cloned.
- 从待克隆的成年动物体细胞（如皮肤或乳腺细胞）中取出二倍体细胞核。
- Insert the donor nucleus into the enucleated egg cell.
- 将供体细胞核插入去核的卵细胞中。
- Stimulate the egg with an electric shock to start cell division, forming an embryo.
- 用电击刺激卵细胞，使其开始分裂，形成胚胎。
- Implant the embryo into the uterus of a surrogate mother.
- 将胚胎植入代孕母亲的子宫。
- The offspring is genetically identical to the donor of the body cell nucleus.
- 后代与提供体细胞核的供体在遗传上完全相同。
Uses include preserving endangered species, producing herds of animals with desirable traits, and potentially producing human stem cells for therapeutic purposes. However, the process is inefficient, often leading to health problems in clones, and raises serious ethical concerns.
用途包括保护濒危物种，培育具有理想性状的动物群体，以及潜在用于生产人类干细胞以进行治疗。然而，该过程效率低下，常导致克隆体出现健康问题，并引发严重的伦理关切。
12. Ethical and Social Issues | 伦理与社会问题
Genetic engineering and cloning provoke debate. Arguments for GM crops include increased food security, reduced chemical usage, and improved nutrition. Arguments against include potential environmental risks, such as genes transferring to wild relatives, and long-term health effects that are not fully understood.
基因工程和克隆引发了争论。支持转基因作物的论点包括增加粮食安全、减少化学品使用和改善营养。反对的论点包括潜在的环境风险，如基因转移至野生近缘种，以及尚未完全了解的长期健康影响。
Animal cloning raises welfare issues: many cloned embryos fail to develop, and cloned animals can suffer from premature ageing and organ defects. Human cloning is broadly condemned for ethical and safety reasons, though therapeutic cloning for producing stem cells remains a subject of regulation.
动物克隆引发了福利问题：许多克隆胚胎无法发育，克隆动物可能患有早衰和器官缺陷。人类克隆因伦理和安全原因而受到广泛谴责，但用于生产干细胞的治疗性克隆仍然是监管的议题。
Aseptic techniques in biotechnology also carry responsibility: preventing the release of genetically modified microorganisms into the environment is critical, so fermenters and disposal methods are carefully controlled.
生物技术中的无菌操作也负有责任：防止转基因微生物释放到环境中至关重要，因此发酵罐和处置方法受到严格控制。
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