Photosynthesis vs. Respiration

Photosynthesis literally means to make with light. It is the process by which plants and some other organisms convert light energy from the sun into chemical energy stored in molecules like glucose, a simple sugar. Photosynthesis takes place in an organelles called chloroplasts. The chloroplasts contain chlorophyll, the pigment that gives plants their green color. Chlorophyll is also the catalyst in the chemical reaction to convert sunlight to chemical energy. It speeds up the chemical reaction. Only organisms with chloroplasts can make their own food. They are called autotrophs. Heterotorphs must obtain energy from an outside source. Animals are examples of heterotrophs.

Photosynthesis and respiration are reversible chemical reactions, meaning that the products of one process are the exact  reactants for the opposite process.

This is the cellular respiration equation.(Image from Gottfried, 1993).

This is the photosynthesis equation (Image from Gottfried, 1993).

Notice that the products from respiration, 6 carbon dioxide molecules and 6 water molecules are the exact reactants and the correct number of them to start the photosynthesis equation.  This clearly demonstrates the balance of life on earth and their interdependence of all life on other organisms.