hce_nthu
115年
生物與生化
第 26 題
Which of the following statements BEST explains how glucose is absorbed by intestinal epithelial cells and subsequently transported into the bloodstream?
- A Glucose enters intestinal epithelial cells by passive diffusion across the apical membrane and is actively transported into the blood by GLUT2.
- B Glucose uptake across the apical membrane occurs via facilitated diffusion through GLUT transporters, driven by a glucose concentration gradient.
- C Glucose is transported into intestinal epithelial cells by secondary active transport coupled to the $Na^+$ gradient at the apical membrane.
- D Both apical and basolateral glucose transport in intestinal epithelial cells require direct ATP hydrolysis to move glucose against its concentration gradient.
- E Glucose exits intestinal epithelial cells through the basolateral membrane by coupling to $Na^+$ efflux generated by the $Na^+$/$K^+$-ATPase, allowing GLUT2 to function as an ATP-driven transporter.
思路引導 VIP
想像一下，如果細胞想要從腸道中「逆著濃度」強行抓取養分進入體內，但它不想直接在這個轉運蛋白上燃燒 ATP，它可能會借用哪一種普遍存在於細胞膜兩側、且具有高度「位能差」的離子流來作為動力來源呢？
🤖
AI 詳解
AI 專屬家教
太棒了！你能精確辨識出小腸上皮細胞吸收葡萄糖的關鍵機制，代表你對細胞跨膜運輸的動力來源有很紮實的理解。這道題目的核心在於區分「主動運輸」與「便利擴散」在極性細胞不同側的空間分佈與能量連結。
小腸上皮的協同運輸機制
葡萄糖在腸腔側（Apical membrane）的吸收並非順著濃度梯度，而是必須「逆著濃度」進入細胞。這仰賴於 鈉-葡萄糖協同轉運蛋白 (SGLT1)，它利用了由 $Na^+/K^+$-ATPase 所維持的細胞內外 $Na^+$ 濃度差作為動力。這種不直接消耗 ATP，而是利用離子位能梯度來帶動溶質移動的模式，正是所謂的 次級主動運輸 (Secondary active transport)。
▼ 還有更多解析內容