(a) Write the name and one function of respiratory pigment found in human beings.

(b) Why do lungs always contain a residual volume of air?

(c) Why is ATP known as energy currency of the living beings?

(a) The respiratory pigment found in human beings is haemoglobin. One of its functions is to transport oxygen from the lungs to the body cells.

(b) Lungs always contain a residual volume of air because the lungs can never be completely emptied of air due to the depression that will be created. If the lungs were completely emptied, the lungs would collapse.

(c) ATP is known as the energy currency of the living beings because it is the energy that is immediately available for various activities like muscle contraction, protein synthesis, membrane transport etc.