osmosis 小問 10 分

certain substances can pass through the plasma membrane(cell) freely while others cannot. The molecules that can move freely through the plasma membrane by simple diffusion are :
1. Lipid-soluble molecules
exp: fatty acids , glycerol, vitamins A,D,E & K..
explain: this is because they can dissolve in the lipid bilayer of the plasme
membrane & move across it easily.

2. Small molecules
exp: oxygen, carbon dioxide & water
reason : small size

there r two types of diffusion too..except for simple diffusion , it is facilitated diffusion

Facilitated diffusion refers to the movement of hydrophilic molecules or ions across the plasma membrane with the help of transport proteins.
exp:amino acids, small acids, small proteins & glucose.
explain: these kind of substances do not pass readily through the phospholipid bilayer,
they diffuse passively into the cill with the help of transport proteins.

sorry that i dunno how to use Cantonese to explain these to you..hope that my explain can help u!!