Cells of all organisms are capable in acquiring the energy necessary to fuel chemical reactions for growth, repair, survival, and reproduction. Photosynthesis & cellular respiration are the main pathways of energy flow in living things. Photosynthesis is a process by which plants and some other organisms convert, light energy from the sun, CO2 from the air & H2O from the earth, into chemical energy stored in molecules like glucose. Cellular respiration is a process in which O2 is delivered to cells in an organism & metabolic process in cells leads to the production of ATP by the breakdown of organic substances.

Cellular Respiration is the process in which glucose is broken down in the presence of oxygen to supply a cell with energy. During cellular respiration the energy stored in organic molecules (glucose) may be released during cellular respiration. This energy is temporarily stored in ATP molecules. In many organisms, the process of cellular respiration is concluded in the mitochondria, in which ATP is produced more efficiently. Oxygen is used and carbon dioxide and water are released as wastes. Cellular respiration does not just occur in humans it occurs in all living things and is important to everything because it is vital. It provides us all with energy to perform work, everyday tasks and body functions. Thus in essence, Cell respiration is responsible for sustaining and maintaining life itself.

Photosynthesis is the process of converting light energy to chemical energy and storing it in bonds of sugar. This process occurs in plants and some algae (Kingdom Protista). Plants need only light energy, CO2 and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts, specifically using chlorophyll, the green pigment involved in photosynthesis. Photosynthesis occurs during times of light. Light is essential for