Cellular respiration is the process by which cells break down glucose (a simple sugar) in the presence of oxygen to produce energy in the form of ATP (adenosine triphosphate). Here are the main molecules needed for cellular respiration:

1. Glucose (C6H12O6): This is the primary fuel source for cellular respiration. It is broken down into smaller molecules, releasing energy.

2. Oxygen (O2): Oxygen is the final electron acceptor in the electron transport chain, the last stage of cellular respiration. It is essential for the production of ATP.

3. Water (H2O): Water is a product of cellular respiration, produced during the electron transport chain.

4. ADP (adenosine diphosphate) and Phosphate (Pi): These molecules are combined to form ATP, the energy currency of the cell.

5. Enzymes: A variety of enzymes are required to catalyze the different chemical reactions in cellular respiration.

6. NAD+ (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide): These are electron carriers that shuttle electrons during the electron transport chain. They are reduced to NADH and FADH2, respectively, and play a crucial role in energy production.

7. Carbon dioxide (CO2): This is a byproduct of cellular respiration, released as a waste product.

It's important to remember that cellular respiration involves a complex series of reactions divided into four main stages: glycolysis, pyruvate oxidation, the Krebs cycle, and oxidative phosphorylation. Each stage requires specific molecules and enzymes to function properly.