What are the raw materials used during photosynthesis?

$(a)$ Bile does not contain any digestive enzyme,yet it is important for the digestion of food. Why?
$(b)$ Name the products formed after the complete digestion of carbohydrates,proteins,and fats in the small intestine.

What is the main toxic waste that the kidneys filter from the blood?

What are the final products produced after the digestion of carbohydrates, proteins, and fats?

$(a)$ How does the exchange of respiratory gases,oxygen and carbon dioxide,take place between tissues and blood in human beings?
$(b)$ Name the respiratory pigment in humans. Where is it found?

$(a)$ Draw the structure of a nephron and label the following parts on it:
$(i)$ Renal artery
$(ii)$ Bowman's capsule
$(iii)$ Glomerulus
$(iv)$ Collecting duct
$(b)$ Name four substances in the initial filtrate which are selectively reabsorbed as the filtrate flows along the tubule.