Excretion

Question 1

A substance that is excreted by plants is oxygen.
State the source of this excreted oxygen [1]

Answer 1

Photosynthesis; [1 mark]

Question 2

One waste product that is excreted from the human body is urea.
Urea is made from excess proteins that can’t be stored in the body.
Excess carbohydrates and lipids do not need to be excreted,
Suggest why excess carbohydrates and lipids do not need to be excreted. [2]

Answer 2

Any two of the following:

Carbohydrates are stored as/converted into glycogen; [1 mark]
Lipids are stored under the skin / around the organs; [1 mark]
Carbohydrates/lipids can be broken down to release energy; [1 mark]