The organisms attain the energy they require from food. Food offers living organisms with the chemical building elements they require to develop and reproduce. The molecules of the food comprise chemical energy, which is discharged when its chemical bonds get dissociated.
The energy stored in the food is articulated in the terms of calories. A calorie refers to the concentration of energy required to elevate the temperature of 1 gram of water by 1 degree Celcius.
The cells break down molecules of food slowly and utilize the energy accumulated in the chemical bonds to generate compounds, like ATP, which power the activities in the cell.