Photosynthesis and cellular respiration are a part of the same energy flow through the food chain among plant and animal life on Earth. Energy from the Sun is brought to Earth via sunlight. The plants absorb this light energy and use it to make simple sugars as food in a process called photosynthesis. So the light energy from the Sun is converted to chemical energy (food). Plants and animals that eat the plants then consume this energy in a process called cellular respiration where the simple carbohydrate energy is converted into ATP, which is the basic energy storage unit of all animals. So the plant energy is converted to ATP and stored until it is needed by the organism. But this all originated as energy from the sunlight that was converted into different forms along the way.