CE BIO diffusion 問題

I would answer your questions in English.

1. Membranes contains pores (holes). A fully permeable membrane have holes large enough for any substances to pass through, while a differentially permeable membrance have holes that is large enough for small particles to pass through only, such as water and metal ions. It usually has nothing to do with carrier molecules.

2. Yes, the substances will pass through the membrance through carrier molecules, and also by simple diffusion through the pores on the membrane.

3. I have answered you in question 2.

Diffusion, osmosis and active transport are very important in Biology. You must ensure that you are familiar with these concepts, in order to study high-level Biology.

2009-05-29 16:42:12 補充：
As a comment on the answer of 唐王, this appears in the Certificate Examinations, and probably a very important topic in the NSS system.
From what I know, many schools in HK teaches the concepts of questions 2 and 3, please don't conclude blindly.

rain lee 唔好吹水喎 diffusion由低conc去高conc?

想問一下differentially permeable membranes 之所以係不一樣的穿透性係咪因為有carrier molecules的關係?!?!
> 不, permeability是因為膜的特性關係, 簡單而言:
分子體積/質量大、帶電荷、帶極性皆不容易穿過細胞膜。
無電荷、油溶性的則較易穿過。
此兩種方法皆屬直接穿過膜的, 不需carrier, 另外有部分特定particles(例如potassium ions)則有特制的carrier, 屬個別例子。
另外, 人工的Dialysis tubing則比較似一個筲箕或篩, 細分子能過大分子不能過, 『所以係不一樣的穿透性』, 很簡單。
　
Also,diffusion時,,,D substances係咪經過carrier molecule 而入去cell 裡面?!?!
> 有小部分是, 大部分不是, 不過即使AL此concept 亦屬out of syllabus, 若不吹毛求疵, 不如就當無carrier 好了。
　
有active transprt 時,,點解同時都可以有diffusion?!?!佢地唔係經過同一樣野既咩?!?!
> Active transport 是必需有carrier 的, 主要是耗用能量將物質由低濃度運輸至高濃度, 而diffusion 是由高濃度走向低濃度, 豈非前功盡廢, 互相抵消?
對此問題, 我有幾種想法
第一, 你誤解了diffusion必需要carrier, 以致有此一問。
第二, Active transport將物質由低濃度運輸至高濃度, 但物質以diffusion型式由膜內洩漏出來。
第三, 以Active transport作diffusion的增速, 所以兩者皆由高濃度運向低濃度。
但第二第三點皆不屬任何中學課程範疇。

2009-05-31 17:38:08 補充：
回樓下 cheung_donald
是嗎? Facilitated diffusion不是out-of-syllabus? 可否請你找一條半條past paper分享一下。

想問一下differentially permeable membranes 之所以係不一樣的穿透性係咪因為有carrier molecules的關係?!?!


係因為個permeable membranes　既成份唔一樣～正如玻璃既係光既穿透性都係唔一樣咁解


D substances係咪經過carrier molecule 而入去
cell 裡面?!?!

係由低ｃｏｎｃ去到高ｃｏｎｃ　佢係自然發生的


有active transprt 時,,點解同時都可以有diffusion?!?!佢地唔係經過同一樣野既咩?!?!

active transprt 時係個ｃｅｌｌ格硬搵ｄ　ｓｕｂｓｔａｎｃｅ　入去既diffusion係由低ｃｏｎｃ去到高ｃｏｎｃ　佢係自然發生的正如你拉緊人去果時果個人都可以沖去你到