问题 单项选择题 A型题

关于药物通过生物膜转运的特点的正确表述是

A.被动扩散的物质可由高浓度区向低浓度区转运,转运的速度为一级速度

B.促进扩散的转运速率低于被动扩散

C.主动转运借助于载体进行,不需消耗能量

D.被动扩散会出现饱和现象

E.胞饮作用对于蛋白质和多肽的吸收不是十分重要

答案

参考答案:A

解析:
本题考查药物通过生物膜的转运机理。
药物通过生物膜的转运机理:(1)被动扩散(passive diffusion)。被动扩散的特点是:从高浓度区(吸收部位)向低浓度区域(血液)顺浓度梯度转运,转运速度与膜两侧的浓度差成正比。扩散过程不需要载体,也不消耗能量,故也称为单纯扩散。膜对通过的物质无特殊选择性,即无饱和现象和竞争抑制现象,一般也无部位特异性。药物大多数以这种方式吸收。被动扩散有二条途径:①溶解扩散,②限制扩散。(2)主动转运 (active transport)。一些生命必需物质(如K+,Na+,I-,单糖,氨基酸,水溶性维生素)和有机酸、碱等 弱电解质的离子型等。主动转运有如下特点:①逆浓度梯度转运,②需要消耗机体能量,能量的来源主要由细胞代谢产生的ATP提供,③主动转运药物的吸收速度与载体数量有关,可出现饱和现象,④可与结构类似的物质发生竞争现象,⑤受代谢抑制剂的影响,⑥主动转运有结构特异性,如 举糖、氨基酸、嘧啶及某些维生素都有本身独立的主动转运特性;⑦主动转运还有部位特异性。(3)促进扩散(facilitateddiffusion)。促进扩散又称中介转运(meadiated transport)或易化扩散,由膜的高浓度一侧向低浓度一侧扩散或转运的过程。促进扩散具有载体转运的各种特征:有饱和现象,与被动扩散不同之处在于:促进扩散不消耗能量,而且是顺浓度梯度转运,转运的速率大大超过被动扩散。(4)胞 饮 作用。胞饮作用是细胞摄取药物的另一种形式,主动变形而将某些物质摄入细胞内或从细胞内释放到细胞外,称为胞饮。某些高分子物质,如蛋白质、多肽类、脂溶性维生素和重金属等,可按胞饮方式吸收。

阅读理解

“This one’s for you,” Sergeant (警官) Barstow shouted and left quickly through the back door. I was a little puzzled. I looked out a window of the Ashfordly Police Station and saw an elderly woman come into the building.

“Good morning, Madam,” I said.

“Good morning,” she said pleasantly. “You’re new, aren’t you?”

“Yes, Madam.”

“It’s about that man who’s been annoying me,” she said. “I’ve been here about him before.”

“Could I have your name and address, please?”  

“Miss Fraser. Josephine Fraser. I live at 43 Prince Terrace. Now, can you please do something about Jackson?”

“What’s he done, Miss Fraser?”

“Done? He’s thrown garbage all over my stairs again. He must be stopped.”

“Where does he live?”

“Next door, Number 41,” she said.  

“I’ll go and see later and warn him off, Miss Fraser.”

“I would be most grateful.” With that she left.

Half an hour later, I reached Prince Terrace. NO. 41 was in a bad state of repair. I knocked. No reply. I entered. The place was deserted. I wondered if the Jackson was a tramp (流浪者). Anyway, it seemed he had left, possibly because of Miss Fraser’s threatening police action. I decided to visit her.

I knocked on her door and it was opened almost immediately. “Ah!” she said gladly. “You’re just in time for coffee.” I followed her inside. Miss Fraser told me more about her battle with Jackson. But when I asked specific questions, it clearly showed that she had never seen Jackson. Finally, I managed to leave.

Sergeant Barstow smiled kindly as I returned. “Nick, did you kick(踢出) Jackson out of that house?”

“Jackson!” I cried. “Who is he?”

“There is no Jackson,” he said. “Miss Fraser is lonely and she likes company. We always let the new young men deal with Miss Fraser. It gives her deep satisfaction. That’s what we are here for, isn’t it — to satisfy the public?”

小题1:Why did Sergeant Barstow leave quickly when Miss Fraser came?

A.Because he wanted to let Nick deal with her alone.

B.Because he had to go and catch Jackson at once.

C.Because he was tired of the elderly woman.

D.Because he knew she would tell a lie.小题2:Miss Fraser told Nick that _____.

A.her neighbor had often caused her trouble

B.it was her first visit to the police station

C.she was looking for Sergeant Barstow

D.someone had broken into her house小题3:Miss Fraser made up the story of Jackson because _____.

A.she liked to play jokes on the policemen

B.she wanted to have someone to talk with

C.she loved to show others her nice coffee

D.she hated Jackson very much

综合题