📚 5.4 Hormonal Communication Exam Practice | 5.4 激素通讯真题精练
Welcome to this focused revision session on 5.4 Hormonal Communication. Hormones are chemical messengers that travel in the blood to coordinate slow, long‑lasting responses throughout the body. In this article, we work through a series of exam‑style questions and clear explanations covering the pancreas, blood glucose regulation, the second messenger model, and the role of adrenaline. Each section alternates between English and Chinese to support bilingual learners and deepen understanding of key A‑level concepts.
欢迎来到 5.4 激素通讯的专项精练。激素是在血液中运输的化学信使，协调全身缓慢而持久的反应。本文将带领大家通过一系列真题风格的问题和清晰讲解，覆盖胰腺、血糖调节、第二信使模型以及肾上腺素的作用。每部分均以中英双语交替呈现，帮助双语学习者加深对 A‑level 核心概念的理解。
1. Hormones and Cell Signalling Overview | 激素与细胞信号概述
Hormones can be classified by their chemical nature. Peptide hormones (e.g. insulin, glucagon) are water‑soluble and bind to receptors on the cell surface membrane, triggering a second messenger cascade inside the cell. Steroid hormones (e.g. oestrogen) are lipid‑soluble and can cross the plasma membrane to bind to intracellular receptors, directly influencing gene transcription.
激素可按化学性质分类。肽类激素（如胰岛素、胰高血糖素）为水溶性，与细胞表面膜上的受体结合，在细胞内引发第二信使级联反应。类固醇激素（如雌激素）为脂溶性，可穿过质膜与胞内受体结合，直接影响基因转录。
Example question: Which of the following hormones acts via an intracellular receptor?
A. Adrenaline B. Insulin C. Testosterone D. Glucagon
例题：下列哪种激素通过胞内受体发挥作用？
A. 肾上腺素 B. 胰岛素 C. 睾酮 D. 胰高血糖素
Answer: C. Testosterone is a steroid hormone. It diffuses through the phospholipid bilayer and binds to a receptor in the cytoplasm or nucleus. Adrenaline, insulin and glucagon are peptide‑derived or amino‑acid‑derived hormones that bind to membrane receptors.
答案：C。睾酮属于类固醇激素，能够扩散通过磷脂双分子层并与细胞质或细胞核中的受体结合。肾上腺素、胰岛素和胰高血糖素均为肽类或氨基酸衍生物，需与膜受体结合。
2. The Pancreas and Blood Glucose Regulation | 胰腺与血糖调节
The pancreas has both exocrine and endocrine functions. The islets of Langerhans contain α‑cells that secrete glucagon and β‑cells that secrete insulin. These hormones work antagonistically to keep blood glucose concentration within a narrow range, typically around 90 mg per 100 cm³ of blood.
胰腺兼具外分泌和内分泌功能。胰岛中的 α 细胞分泌胰高血糖素，β 细胞分泌胰岛素。这两种激素相互拮抗，使血糖浓度维持在一个较窄的范围内，通常约为每 100 cm³ 血液 90 mg。
Question: Describe how the β‑cells in the pancreas detect an increase in blood glucose and respond by secreting insulin.
问题：描述当血糖升高时，胰腺 β 细胞如何感知变化并通过分泌胰岛素作出响应。
Model answer: Glucose enters β‑cells via facilitated diffusion through GLUT2 transporters. Inside the cell, glucose is phosphorylated and metabolised, producing ATP. The rise in ATP closes ATP‑sensitive K⁺ channels, depolarising the membrane. This opens voltage‑gated Ca²⁺ channels, causing an influx of Ca²⁺ ions. The increase in intracellular Ca²⁺ triggers the exocytosis of insulin‑containing vesicles.
参考答案：葡萄糖经 GLUT2 转运蛋白的易化扩散进入 β 细胞。在细胞内，葡萄糖被磷酸化并代谢，产生 ATP。ATP 的增加关闭 ATP 敏感的 K⁺ 通道，使膜去极化。这一变化打开电压门控 Ca²⁺ 通道，导致 Ca²⁺ 内流。胞内 Ca²⁺ 浓度升高触发含胰岛素的囊泡发生胞吐。
3. Insulin: Mechanism and Effects | 胰岛素：作用机制与效应
Insulin lowers blood glucose by binding to receptor tyrosine kinases on target cells such as hepatocytes and muscle cells. This triggers a signalling cascade that increases the translocation of GLUT4 glucose transporters to the cell membrane, enhancing glucose uptake. Insulin also activates enzymes for glycogenesis (glucose → glycogen) and stimulates the conversion of glucose to fat in adipose tissue.
胰岛素通过结合靶细胞（如肝细胞和肌细胞）上的受体酪氨酸激酶来降低血糖。这一结合触发信号级联反应，增加 GLUT4 葡萄糖转运蛋白向细胞膜的移位，从而增强葡萄糖摄取。胰岛素还激活糖原生成（葡萄糖 → 糖原）相关的酶，并刺激脂肪组织中葡萄糖转化为脂肪。
Exam tip: Always link insulin to an increase in the number of GLUT4 proteins in the membrane, not just to ‘making membranes more permeable’. The phrase ‘translocation of GLUT4’ scores the highest marks.
考试提示：务必将胰岛素与膜上 GLUT4 蛋白数量的增加联系起来，而不仅仅是“使膜通透性增大”。使用“GLUT4 的移位”这一表述能够获得最高分数。
Practice statement: Explain why a person with untreated type 1 diabetes may lose weight despite a high‑calorie diet.
练习题：请解释为何未经治疗的 1 型糖尿病患者即使饮食热量高仍可能体重下降。
English explanation: Without insulin, cells cannot take up glucose efficiently. The body turns to fat and protein reserves for energy, causing muscle wasting and loss of adipose tissue. Glucose is also excreted in urine, taking water and calories with it.
中文解释：缺乏胰岛素时，细胞无法有效摄取葡萄糖，身体转而消耗脂肪和蛋白质储备供能，导致肌肉萎缩和脂肪组织减少。此外，葡萄糖随尿液排出，带走水分和热量。
4. Glucagon: Mechanism and Effects | 胰高血糖素：作用机制与效应
When blood glucose falls, α‑cells secrete glucagon. Glucagon binds to membrane receptors on hepatocytes, activating adenylate cyclase. The resulting increase in cyclic AMP (cAMP) activates protein kinase A, which in turn phosphorylates enzymes involved in glycogenolysis (breakdown of glycogen to glucose) and gluconeogenesis (synthesis of glucose from non‑carbohydrate sources such as amino acids and glycerol).
当血糖降低时，α 细胞分泌胰高血糖素。胰高血糖素与肝细胞膜受体结合，激活腺苷酸环化酶。随之升高的环腺苷酸 (cAMP) 激活蛋白激酶 A，该激酶继而磷酸化参与糖原分解（糖原分解为葡萄糖）和糖异生（由氨基酸和甘油等非碳水化合物合成葡萄糖）的酶。
Key equation for glycogenolysis:
Glycogen(n) + Pi → Glycogen(n‑1) + Glucose‑1‑phosphate
糖原分解的关键方程式：
糖原(n) + 磷酸 → 糖原(n‑1) + 葡萄糖‑1‑磷酸
Question: The hormone glucagon only affects liver cells. Explain why liver cells respond to glucagon but muscle cells do not.
问题：胰高血糖素仅影响肝细胞。解释为何肝细胞对胰高血糖素作出响应而肌细胞不响应。
Answer: Muscle cells lack glucagon receptors. The liver expresses glucagon receptors and also contains glucose‑6‑phosphatase, the enzyme needed to release free glucose into the blood. Muscle cells cannot release free glucose because they lack this enzyme; glycogen in muscle is used locally for contraction.
答案：肌细胞缺乏胰高血糖素受体。肝细胞表达胰高血糖素受体，并含有葡萄糖‑6‑磷酸酶，该酶是将游离葡萄糖释放入血所必需的。肌肉细胞因缺乏此酶而无法释放游离葡萄糖；肌糖原仅用于局部供能收缩。
5. The Second Messenger Model (cAMP) | 第二信使模型 (cAMP)
The second messenger model explains how a water‑soluble hormone (the first messenger) can bring about a cellular response without entering the target cell. Adrenaline and glucagon both use this pathway. The hormone binds to a complementary receptor, causing the associated G‑protein to activate adenylate cyclase. This enzyme converts ATP to cyclic AMP (cAMP), which then activates a cascade of phosphorylation events.
第二信使模型解释了水溶性激素（第一信使）如何在不进入靶细胞的情况下引发细胞响应。肾上腺素和胰高血糖素均利用此途径。激素与互补受体结合，使关联的 G 蛋白激活腺苷酸环化酶。该酶将 ATP 转化为 cAMP，随后激活一系列磷酸化事件。
The central reaction:
ATP → cAMP + PPᵢ
核心反应：
ATP → cAMP + PPᵢ
Exam question: Outline the role of cAMP in the action of glucagon.
考试题：概述 cAMP 在胰高血糖素作用中的角色。
Model answer: cAMP acts as a second messenger. It activates protein kinase A, which phosphorylates and activates glycogen phosphorylase, leading to glycogenolysis. cAMP also modulates enzymes for gluconeogenesis. Its effects are amplified at each step of the cascade.
参考答案：cAMP 作为第二信使，激活蛋白激酶 A，该激酶磷酸化并激活糖原磷酸化酶，导致糖原分解。cAMP 还调节糖异生相关酶。级联放大的每一步都能增强信号效应。
Common pitfall: Some students confuse cAMP with the hormone itself or with ATP. Remember: cAMP is the intracellular second messenger; the hormone remains outside the cell.
常见错误：部分学生将 cAMP 与激素本身或 ATP 混淆。请记住：cAMP 是胞内第二信使；激素始终留在细胞外。
6. Adrenaline as a Hormone | 肾上腺素作为激素
Adrenaline is produced by the adrenal medulla in response to stress or low blood glucose. Like glucagon, it activates glycogenolysis in the liver, but it does so via a slightly different receptor (adrenergic receptor). Adrenaline also promotes lipolysis in adipose tissue and increases heart rate, preparing the body for ‘fight or flight’.
肾上腺素由肾上腺髓质在应激或低血糖时分泌。与胰高血糖素类似，它激活肝糖原分解，但通过稍有不同的受体（肾上腺素能受体）实现。肾上腺素还促进脂肪组织中的脂肪分解并加快心率，使机体做好“战或逃”的准备。
Compare and contrast: Adrenaline and glucagon both raise blood glucose, but adrenaline has a broader range of targets and effects because its receptors are present on many cell types, including those of the cardiovascular system.
比较与对比：肾上腺素和胰高血糖素均能升高血糖，但肾上腺素的作用靶点和效应更为广泛，因为其受体存在于包括心血管系统在内的多种细胞类型。
Data‑based question: An experiment measures blood glucose after injection of adrenaline in a healthy volunteer. Explain the shape of the resulting curve (rapid rise followed by a gradual decline).
数据题：测量健康志愿者注射肾上腺素后的血糖变化。解释所得曲线形状（快速上升后逐渐下降）。
Explanation: Adrenaline rapidly stimulates glycogenolysis in the liver, causing a quick rise in blood glucose. As adrenaline is metabolised and its signal fades, insulin secretion increases in response to the elevated glucose, promoting glucose uptake and glycogenesis, which brings glucose levels back down.
解释：肾上腺素迅速刺激肝糖原分解，导致血糖快速上升。随着肾上腺素被代谢、信号衰减，胰岛素因高血糖而分泌增加，促进葡萄糖摄取和糖原生成，使血糖水平回落。
7. Comparing Hormonal and Nervous Communication | 激素通讯与神经通讯对比
It is essential to be able to compare the endocrine and nervous systems. The table below summarises the key differences.
能够比较内分泌系统与神经系统至关重要。下表概述了主要区别。
| Feature | Hormonal Communication | Neuronal Communication |
|---|---|---|
| Transmission | Chemical signal via blood | Electrical and chemical (synapse) |
| Speed | Slow (seconds to hours/days) | Very fast (milliseconds) |
| Duration | Long‑lasting | Short‑lived |
| Target | Cells with specific receptors (may be widespread) | Specific cells at synapse (localised) |
尽管激素作用较慢，但其效应持久且可同时影响遍布全身的多个靶组织。神经通讯则精确、快速，适合即时反应。
Exam question: Explain one advantage of hormonal over neuronal communication.
考试问题：解释激素通讯相较于神经通讯的一个优势。
Sample answer: Hormonal signals can reach virtually all cells in the body via the bloodstream, provided those cells possess the correct receptor. This allows a single chemical messenger to coordinate a widespread, long‑term response such as growth or reproduction.
示例答案：激素信号可通过血流几乎到达全身所有（带有合适受体的）细胞。这使得单个化学信使能够协调如生长或繁殖这样广泛而长期的响应。
8. Multiple‑Choice Question Practice | 选择题练习
Try these quick questions to test your recall.
尝试以下快速问题，检验你的记忆。
Q1. Which statement about the second messenger model is correct?
A. The hormone enters the cell and binds to DNA.
B. The hormone‑receptor complex activates a G‑protein.
C. ATP is converted directly to glucose.
D. cAMP acts as the first messenger.
Q1. 关于第二信使模型的哪项陈述是正确的？
A. 激素进入细胞并与 DNA 结合。
B. 激素‑受体复合物激活 G 蛋白。
C. ATP 直接转化为葡萄糖。
D. cAMP 作为第一信使。
Q2. Which hormone is released when blood glucose drops below normal?
A. Insulin B. Glucagon C. Oestrogen D. Thyroxine
Q2. 当血糖低于正常值时释放哪种激素？
A. 胰岛素 B. 胰高血糖素 C. 雌激素 D. 甲状腺素
Answers: Q1 – B; Q2 – B. Review the earlier sections if you missed either answer.
答案：Q1 – B；Q2 – B。若答错请回顾前面小节。
9. Structured Question: Type 1 Diabetes and Insulin Therapy | 结构化问题：1 型糖尿病与胰岛素治疗
Extended response question: Type 1 diabetes results from the autoimmune destruction of pancreatic β‑cells. Discuss how this condition is managed using insulin therapy and explain why insulin must be injected rather than taken orally.
扩展问答题：1 型糖尿病源于胰腺 β 细胞的自身免疫性破坏。讨论此病如何通过胰岛素疗法管理，并解释为何胰岛素必须注射而不能口服。
Guidance for answer (English): Patients monitor blood glucose and inject recombinant human insulin before meals. The dosage is adjusted based on carbohydrate intake and activity level. Insulin is a peptide hormone; if swallowed, it would be digested by proteases in the stomach and small intestine, losing its biological activity. Therefore, injection bypasses the digestive system and delivers functional insulin directly into the bloodstream.
答题指导（中文）：患者监测血糖，并在餐前注射重组人胰岛素。剂量根据碳水化合物摄入量和活动水平调整。胰岛素是肽类激素，若口服会被胃和小肠中的蛋白酶消化，失去生物活性。因此注射可绕过消化系统，将功能性胰岛素直接输送到血液中。
Examiner’s tip: Always link protein digestion to the inactivation of peptide hormones. A common mistake is simply saying ‘stomach acid destroys insulin’ — acid denatures proteins but the key point is proteolytic enzymes.
考官提示：务必将蛋白质消化与肽类激素的失活关联起来。常见错误是简单地说“胃酸破坏胰岛素”——酸会使蛋白质变性，但核心要点在于蛋白酶的水解作用。
10. Data Analysis: Glucose Tolerance Test | 数据分析：葡萄糖耐量试验
An oral glucose tolerance test (OGTT) is used to diagnose diabetes. A patient fasts overnight, then drinks a solution containing 75 g of glucose. Blood glucose is measured at intervals. The graph below represents typical results for a healthy individual and a person with untreated type 1 diabetes.
口服葡萄糖耐量试验 (OGTT) 用于诊断糖尿病。患者禁食过夜后饮用含 75 g 葡萄糖的溶液，再间隔测定血糖浓度。下图代表健康个体与未经治疗的 1 型糖尿病患者典型结果。
(Imagine a graph: healthy curve rises to ~140 mg/dL at 30 min and returns to baseline by 2 h; diabetic curve starts higher, rises steeply above 200 mg/dL and remains elevated.)
（想象曲线：健康者 30 min 上升至约 140 mg/dL，2 h 回到基线；糖尿病者起点更高，陡升至 200 mg/dL 以上且持续偏高。）
Question: Explain why the blood glucose of the diabetic person remains high two hours after ingestion.
问题：解释为何糖尿病患者在摄入葡萄糖两小时后血糖依然居高不下。
Answer: Lack of insulin prevents the uptake of glucose into liver and muscle cells, and fails to promote glycogenesis. Moreover, without insulin, gluconeogenesis continues unopposed. Consequently, glucose entering the blood from the gut is not removed efficiently.
答案：缺乏胰岛素阻止了葡萄糖进入肝细胞和肌细胞，也无法促进糖原生成。此外，缺乏胰岛素时糖异生过程不受抑制。因此，从肠道入血的葡萄糖无法被有效清除。
11. Common Misconceptions and Key Terminology | 常见误解与关键术语
Clarify these points before your exam:
考前请厘清以下几点：
Misconception: ‘Glucagon converts glycogen to glucose.’
Correction: Glucagon triggers a signalling cascade that activates glycogen phosphorylase. The enzyme, not the hormone, breaks down glycogen. Describe it as ‘glucagon stimulates glycogenolysis’.
误解：“胰高血糖素将糖原转化为葡萄糖。”
纠正：胰高血糖素触发信号级联反应，激活糖原磷酸化酶。分解糖原的是酶而非激素。应表述为“胰高血糖素刺激糖原分解”。
Misconception: ‘All hormones use the second messenger model.’
Truth: Only water‑soluble hormones that cannot cross the plasma membrane rely on second messengers. Steroid and thyroid hormones enter cells and bind to intracellular receptors.
误解：“所有激素都采用第二信使模型。”
事实：只有不能穿越质膜的水溶性激素依赖第二信使。类固醇和甲状腺激素可进入细胞并与胞内受体结合。
Essential terms: glycogenolysis, gluconeogenesis, glycogenesis, adenylate cyclase, protein kinase A, translocation of GLUT4, glucose‑6‑phosphatase, islets of Langerhans.
必要术语：糖原分解、糖异生、糖原生成、腺苷酸环化酶、蛋白激酶 A、GLUT4 的移位、葡萄糖‑6‑磷酸酶、胰岛。
最后冲刺：在回答中若用到“磷酸化级联反应”，请解释其含义为酶的顺序激活，导致信号放大。
12. Final Exam‑Style Challenge | 终极真题挑战
Combined question: A lab mouse is injected with a toxin that selectively destroys α‑cells in the pancreas. Predict and explain the effect on the mouse’s blood glucose concentration after a 24‑hour fast. Use the following terms in your answer: glucagon, glycogenolysis, gluconeogenesis, blood glucose homeostasis.
综合题：一只实验小鼠被注射能选择性破坏胰岛 α 细胞的毒素。预测并解释禁食 24 h 后小鼠血糖浓度的变化，在答案中请使用：胰高血糖素、糖原分解、糖异生、血糖稳态。
Model answer: With α‑cells destroyed, the mouse cannot secrete glucagon in response to low blood glucose. During fasting, glucagon normally stimulates glycogenolysis and gluconeogenesis in the liver to release glucose. Without glucagon, these pathways are not activated, and blood glucose will fall to dangerously low levels, impairing brain function. Homeostasis fails because the antagonistic pair (insulin and glucagon) is unbalanced.
参考答案：α 细胞被破坏后，小鼠无法针对低血糖分泌胰高血糖素。禁食期间，胰高血糖素通常刺激肝糖原分解和糖异生以释放葡萄糖。缺乏胰高血糖素时，这些通路不被激活，血糖将降至危险水平，影响脑功能。由于拮抗激素对（胰岛素与胰高血糖素）失衡，稳态崩溃。
This type of question tests your ability to apply knowledge of negative feedback and the specific roles of pancreatic cells. Practice linking cell function to endocrine communication.
此类题目考查你对负反馈知识以及胰腺细胞特定角色的应用能力。练习将细胞功能与内分泌通讯联系起来。
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