Basics of Biology

Molecules and Biology

What are some common energy sources for cells?

Various molecules have certain energy, and those can be used by cells (the kilocalorie/gram is also expressed as kilogram calorie, or the amount of heat required to raise the temperature of water one degree Celsius). The following chart lists the energy source and the kilocalorie per gram energy yield for the cells:







Energy source

Energy yield








4 kilocalories/gram







Fat (lipids)

9 kilocalories/gram








4 kilocalories/gram


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