section 3 (4) explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms

Question 1

What is diffusion?

Answer 1

the movement of a substance from a place of high concentration to low concentration

Question 2

What is osmosis?

Answer 2

The movement of water across a semi-permeable membrane to a place of lower concentration

Question 3

Why is diffusion inadequate in the removal of dissolved nitrogenous wastes in some organisms?

Answer 3

• passive transport: SLOW
• more useful over short distances (between cells)
• wastes are only able to move down a concentration gradient and movement would slow as equilibrium is approached. this may mean that, for example, urea would not be able to be excreted from the bloodstream

Question 4

Why is osmosis inadequate in the removal of dissolved nitrogenous wastes in some organisms?

Answer 4

• does not enable the removal of nitrogenous wastes; only able to dilute them
• may cause too much water to be lost from the body in urine; if the urine has a high concentration of nitrogenous wastes, more water is drawn into the urine through osmosis