In the second half of the 1700s, a scientist by the name of Joseph Priestley conducted a groundbreaking experiment that nicely demonstrates the tight relationship that exists between cellular respiration and photosynthesis. His experiment was quite simple. He placed a mouse in a sealed container, and the end result was that the mouse would suffocate to death. Priestley's next step was to place a green plant into the same jar with a new mouse. What he discovered was that the mouse didn't suffocate to death. Priestly realized that the plant was somehow "refreshing" the air within the sealed container. Today we know that this refreshment of air was due to the fact that the plant was gathering the carbon dioxide released by the mouse and releasing oxygen back into the jar. This process is called photosynthesis.

The equation is a fairly simple equation:

carbon dioxide + water `->` glucose + oxygen

Light energy is the fuel source for that reaction. The items on the left are the raw materials, and the glucose and oxygen are the products of photosynthesis.

Cellular respiration is quite similar. In fact, you could flip the arrow around, and that would be the equation for cellular respiration, but equations are written from left to right.

glucose + oxygen `->` carbon dioxide + water

That means the products of photosynthesis become the raw materials for cellular respiration, and cellular respiration's products are the raw materials needed for photosynthesis.

Let me start by answering the final question. Yes, cellular respiration without photosynthesis is possible as long as the oxygen and glucose that cellular respiration requires are supplied via some alternative mechanism.

As the question indicates, photosynthesis and cellular respiration are closely related to each other. The equation for cellular respiration is essentially the equation for photosynthesis backwards.

Photosynthesis occurs within a chloroplast and uses chlorophyll to absorb the light energy that is necessary to fuel the following equation.

carbon dioxide + water → glucose + oxygen

Cellular respiration's equation is the following equation.

glucose + oxygen → carbon dioxide + water

As you can see, the products of photosynthesis are the raw materials for cellular respiration, and cellular respiration's products are the raw materials necessary for photosynthesis.

Cellular respiration occurs in the mitochondria of a cell, and that organelle is often called the powerhouse of the cell. The goal of cellular respiration isn't the production of carbon dioxide and water. The goal of cellular respiration is to use the oxygen and glucose to produce another form of energy called adenosine triphosphate (ATP). ATP is an organic chemical that provides the energy that living organisms need to drive processes within cells and organs. Things like muscle contractions and nerve impulse propagation are dependent on ATP energy.