Depends on the grade you are teaching but their are a few ways I add a visual or hands on component to my Photosynthesis and Cellular Respiration lesson. The link below is just a nice intro demo that is cheap and easy, I dont frontload or tell them anything, just have them observe and come up with their own ideas to explain the phenomena.
Once I dive into the process of photosynthesis I use clay and toothpicks to have them make models of each step of the equation. You can continue this with cellular respiration if you would like too, I like to keep them together so we can talk about the importance of the reactions and products for each of the reactions to be able to happen.
Then for cellular respiration I do a yeast lab to show how organisms can turn sugars into carbon dioxide and different liquid products, in this case alcohol. You can find this lab on you tube but you basically just mix warm water, yeast and sugar in a bottle and put a balloon on top to capture, and measure, the CO2. You can even let them compare different sugars to see which one makes the biggest ballon (produces the most ATP).
Good luck and let me know if you want any more information or more detailed explanations on any of these ideas.