The parts P and Q are present only in plant cells, they are not present in animal cells. The part P contains a green pigment called R whereas part Q is made of a tough material S. The part P takes part in the food making process whereas part Q gives shape and support to the plant cell.
P is chloroplast
R is chlorophyll
Q is Cell wall
S is cellulose
Chloroplast contains green pigments which take part in the food making process called photosynthesis. Whereas the cell wall is made up of cellulose which gives shape and support to the plant cell.