hce_nthu
115年
生物與生化
第 39 題
A researcher subjects four distinct biological structures (a functional globular protein, a segment of DNA, a cellulose fiber, and a molecule of amylopectin) to an environment where all non-covalent interactions (hydrogen bonds, ionic bonds, van der Waals forces, and hydrophobic interactions) are completely disrupted, but all covalent bonds (peptide bonds, glycosidic linkages, and phosphodiester linkages) remain intact. Which resulting observation is the LEAST accurate regarding the stable molecular components remaining after this treatment?
- A The globular protein, such as transthyretin, would be converted into a nonfunctional, linear polypeptide chain, retaining its unique amino acid sequence.
- B The secondary structure elements (such as $\alpha$-helices and $\beta$-pleated sheets) within the polypeptide backbone of the globular protein would no longer exist.
- C The two complementary strands of the DNA double helix would separate entirely, resulting in two distinct, single polynucleotide strands.
- D The amylopectin molecule (a storage polysaccharide) would be cleaved into hundreds of individual glucose monomers.
- E A cellulose molecule would retain its straight, unbranched configuration, although it would no longer be grouped into strong microfibrils.
思路引導 VIP
請試著思考：如果我們把一串用強力膠黏好的珍珠項鍊，只是用力拆掉用來固定項鍊造型的魔鬼氈或磁鐵扣，這串項鍊會從此斷成一顆顆散落的珍珠，還是依然維持著原本那一長條黏好的結構呢？這與單體之間的連結方式有什麼關係？
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AI 詳解
AI 專屬家教
恭喜你準確地辨別了化學鍵結的本質！這題展現了你對生物大分子結構極為清晰的理解。這類題目的鑑別度在於考生是否能冷靜地區分「一級結構（共價鍵維持）」與「空間構形（非共價交互作用維持）」的差異。你成功抓住了題目核心：環境僅破壞非共價鍵，因此分子內部的共價骨架應保持完整。
糖苷鍵的穩定性
在選項 (D) 中，支鏈澱粉 (amylopectin) 是一種高度分支的葡萄糖聚合物，其分子鏈是由 $\alpha-1,4$ 與 $\alpha-1,6$ 糖苷鍵 (glycosidic linkages) 連結而成的。由於糖苷鍵屬於強大的共價鍵，在不涉及化學水解或酵素催化的情況下，僅僅破壞氫鍵或凡得瓦力是無法將其切斷的。因此，支鏈澱粉雖然會失去其特定的空間摺疊，但絕對不會被降解成數百個獨立的葡萄糖單體。
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