What are the two chemicals that make up a cell?

Question

and what is cellular respiration?

Answer 1

There are HUNDREDS of chemicals that make up even the simplest cell.

Answer 2

There are far more than two chemicals that make up a cell.
But a simplified list would probably look like:
DNA in the nucleus.
RNA in both the nucleus and cytoplasm.
Phospholipids in all the membrane systems.
Proteins everywhere (in membranes and in solution).
Individual amino acids free in the cytoplasm.
Carbohydrates as energy stores, and as accessory moeties on plasma membrane proteins.
Water as the solvent throughout the whole cell.
Mononucleotides (ADP/ATP, GTP/GDP, etc.) dissolved in the cytoplasm and in the nucleus.

And cellular respiration is the process of breaking down sugars (principally glucose) by oxidation, creating water and carbon dioxide, and providing chemical energy in the process.