Plants have an organelle called chloroplasts which contain the pigment chlorophyll. Chlorophyll absorbs sunlight, and the chloroplasts use the energy from the sunlight to create glucose. Stomata take carbon dioxide and roots take water for the plants. Thus by the process of photosynthesis they make their food. But Animal Cells don't have the chloroplasts nor they take carbon dioxide. So they can't perform the process of photosynthesis. That's why animals cant make their food from carbon dioxide and water.