[F.3 biology] osmosis

樓上果位人兄=-= starch 又點會有solution--starch唔係insoluble既咩=-= so that 唔會affect到water potential 丫麻--
仲有要搞清楚咩叫osmosis ~ for instance, 張一個potato 浸落 high concentration既
glucose solution到 個potato一陣就會淋左 由於potato入面既 cell 既water potential 高過出面 所以d水份子就出左去d 糖水到

conclusion

要有2 osmosis 要有兩種唔同water potential 既soution 同 埋要有 一個 selectively membrane

sucrose sloution 可以睇到osmosis 係因為佢夠大粒 pass 唔過個membrane 所以
所發生既一定係osmosis而唔係diffusion 但係 glucose d份子細..可以穿過個membrane so that diffusion同 osmosis同時發生 如果你只係要睇osmosis 咁就唔得了 因為diffusion of glucose solution 會影響到個osmosis既速度嫁

2010-06-17 14:10:18 補充：
仲有 一d disaccharide 既糖水都做得到 但係你要分到個water potential 一定要有gradient

osmosis要用sucrose solution,not glucose solution 因爲glucose 的 molecular size 太小, 比dialysis tubing 的pores 細，所以glucose molecules will move from the more concentrated glucose solution to the region of lower glucose concentration by diffusion.

As diffusion occurs, the water potential of the 2 regions will become the same. Since there's no water potential difference, osmosis cannot occur. So, glucose solution cannot be used to show osmosis.

但sucrose molecules size is larger, water molecules move instead of sucrose. water molecules move from a region of higer water potential to a region of lower water potential by osmosis. 所以sucrose solution可以show 到osmosis.

除了sucrose solution，starch solution 都可以show 到osmosis因爲它的molecular size 比 d pores 大。