Define osmosis and explain why osmosis is a special form of diffusion.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

1. [7] movement + molecules ;
2. [7] water;
3. [7] water potential;
4. [7] high to low;
5. [7] until concentrations equal either side / equilibrium / force applied to prevent it ;
6. [7] (osmosis) partially permeable AW membrane ;
7. [7] (diffusion) membrane not required;
8. [7] energy not required AW ;
9. [3] by villi;
10. [3] absorption / uptake;
11. [3] of digested carbohydrate / glucose / amino acids / fatty acids / glycerol / minerals / ions or salts or named ;
12. [3] faster than diffusion;
13. [3] against a concentration gradient ;
14. [3] to prevent wastage / egestion AW ;