Biochemistry & Metabolism — Common Exam Question Types

1.Common question: given experimental data on Km and Vmax changes, identify the type of enzyme inhibition.

常見問法：給定實驗數據（Km 和 Vmax 的變化），判斷酵素抑制類型。

2.Strategy. If Km increases and Vmax stays unchanged, it is competitive inhibition — the inhibitor competes with substrate for the active site, but high substrate can overcome it.

解題策略。若 Km 增大、Vmax 不變，是競爭性抑制——抑制劑與受質競爭活性位點，但高受質濃度可克服。

3.If Km stays unchanged and Vmax decreases, it is noncompetitive inhibition — the inhibitor binds elsewhere, reducing effective enzyme count, cannot be overcome by adding substrate.

若 Km 不變、Vmax 降低，是非競爭性抑制——抑制劑結合在他處，減少有效酵素數量，加受質無法克服。

4.If both Km and Vmax decrease, it is uncompetitive inhibition — the inhibitor only binds the enzyme-substrate complex.

若 Km 和 Vmax 都降低，是非拘束性抑制——抑制劑只結合酵素受質複合物。

5.If you see a sigmoidal velocity curve in a multi-subunit enzyme, it is allosteric regulation, often with cooperative binding.

若看到 S 形速率曲線且為多亞基酵素，是異位調控，通常伴隨協同結合。

6.Common question: how many ATP are produced from complete oxidation of one glucose molecule? How many if a certain step is blocked?

常見問法：一分子葡萄糖完全氧化產生多少 ATP？某步驟阻斷後產生多少？

7.Strategy. Memorize direct products of each stage: ATP, NADH, FADH2. Conversion: each NADH yields about two point five ATP via the electron transport chain. Each FADH2 yields about one point five ATP. Note the shuttle system loss for cytoplasmic NADH from glycolysis.

解題策略。記住每階段的直接產物：ATP、NADH、FADH2。換算：每個 NADH 經電子傳遞鏈產生約 2.5 個 ATP，每個 FADH2 產生約 1.5 個 ATP。注意醣解產生的細胞質 NADH 有穿梭系統的能量損耗。

8.Common question: given a metabolic toxin, identify which step it blocks and the consequence.

常見問法：給定代謝毒物，問它阻斷哪個步驟、後果為何。

9.Cyanide blocks Complex IV — stops electron transport chain, no ATP, lethal. Rotenone blocks Complex I — blocks NADH electron entry, major ATP reduction. Antimycin A blocks Complex III — between coenzyme Q and cytochrome c.

氰化物 cyanide 阻斷 Complex IV——停止電子傳遞鏈，無 ATP，致死。Rotenone 阻斷 Complex I——阻斷 NADH 電子進入，ATP 大減。Antimycin A 阻斷 Complex III——介於輔酶 Q 和細胞色素 c 之間。

10.Oligomycin blocks ATP synthase — H plus return is stopped, no ATP synthesis. DNP, dinitrophenol, is an uncoupler — H plus freely crosses membrane, proton gradient dissipates, energy lost as heat.

Oligomycin 阻斷 ATP 合成酶——H 質子無法回流，ATP 合成停止。DNP 解偶聯劑——H 質子自由穿膜，質子梯度消散，能量以熱散失。

11.Fluoride blocks enolase in glycolysis step nine. Arsenic replaces phosphate in glycolysis step seven, causing arsenolysis with no ATP yield.

Fluoride 阻斷醣解步驟 9 的 enolase。砷 arsenic 取代磷酸進入醣解步驟 7，造成 arsenolysis，無 ATP 產生。

12.Common question: what metabolic pathways do insulin or glucagon promote or inhibit?

常見問法：胰島素或升糖素促進或抑制哪些代謝路徑？

13.One principle: Insulin equals STORE — lowers blood glucose by promoting glycolysis, glycogen synthesis, and lipogenesis.

一個原則：胰島素等於儲存——降低血糖，促進醣解、肝醣合成、脂肪合成。

14.Glucagon equals RELEASE — raises blood glucose by promoting glycogen breakdown (glycogenolysis), gluconeogenesis, and lipolysis.

升糖素等於釋放——升高血糖，促進肝醣分解、糖質新生、脂肪分解。