Photosynthesis takes the carbon dioxide and water to produce carbohydrates and oxygen, while cellular respiration uses carbohydrates and oxygen to obtain energy and has carbon dioxide and water as produce.
This means that both processes have an important role in the carbon cycle.
Carbon is found in the atmosphere as carbon dioxide, and it passes to the biosphere via photosynthesis, in the form of carbohydrates. Then carbon returns to the atmosphere via cellular respiration.
In the hydrosphere, the carbon is also found as carbon dioxide, just dissolved in the water from the atmosphere. This means that a similar process to the one between the atmosphere and biosphere occurs between the hydrosphere and biosphere.
Carbon is found in the geosphere as part of the rocks, and it passes to the atmosphere as carbon dioxide when volcanoes erupt or fossil fuels are burnt.
When organisms (biosphere) decompose, part of the carbon forms the soil, and eventually rocks (geosphere), while part is released into the atmosphere as carbon dioxide.