Energy and Life

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Energy comes in many forms on this planet, including light, heat, and electricity. Energy can also be stored in chemical molecules as well.

When we refer to energy in living organisms, we are referring to a molecule called ATP. ATP = adenosine triphosphate.

ATP is a nucleic acid. You can see that it looks similar to a nucleotide. ATP Nucleotide

ATP consists of: 1) a nitrogen base called adenine 2) a sugar called ribose, and 3) three phosphate groups.

It is the phosphate groups that are key to ATP’s ability to store and release energy.

ADP or adenosine diphosphate is similar to ATP but has 2 phosphate groups instead of 3.

Living things can store energy by adding a phosphate to ADP, turning it into ATP. ADP is like a rechargeable battery that powers a cell. Cells can then release the energy in ATP by breaking the bonds between the second and third phosphate.

So, ATP can easily release and store energy by breaking and re-forming the bonds between its phosphate groups. This makes it exceptionally useful as an energy source for cells.

Cells are not “born” with a supply of ATP Cells are not “born” with a supply of ATP. So where do we, humans, get ATP? From food. Because we must consume living things to obtain energy, we are known as heterotrophs (“different-feeders”).

Originally, all the energy in all food comes from the sun Originally, all the energy in all food comes from the sun. Organisms that are able to use the sun to synthesize their own food molecules are called autotrophs (“self-feeders”). This is done by the process of photosynthesis.