Energy Storage in the Body

The Molecules Involved:

	Adenosine Triphosphate (ATP)
Because you don't eat 24 hours a day, your body must have some way to store the chemical potential energy found in your food so that you can use it later. The primary energy storage molecule is Adenosine Triphosphate or ATP. It looks like the molecule you see to the right (try dragging it around for a better look):

It is formed from Adenosine Diphosphate or ADP and Phosphate or P_i:

Adenosine Diphosphate (ADP)	Phosphate (Pi)

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Chemical potential energy is stored when ADP bonds to Pi forming ATP and Water:

ADP	+	Pi	--->	ATP	+	H2O
Let's represent this symbolically as: ADP-OH + Pi-H ---> ATP + H2O Color code the molecules Reset the colors. Show the bonds that break Show the bonds that form

As you can see above, two bonds are broken and two bonds form. Because the bonds that form have more chemical potential energy, some other form of energy was stored in the ATP and H₂O. This means that the new bond formed between ADP and P_i is weaker and less stable than the previous bond between ADP and OH. This formed the more unstable ATP molecule with greater chemical potential energy.

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When the above reaction runs in the reverse so that ATP combines with Water to form ADP and P_i, chemical potential energy is reduced by being converted to other forms of energy:

ATP	+	H2O	--->	ADP	+	Pi
Let's represent this symbolically as: ATP + H2O ---> ADP-OH + Pi-H Color code the molecules Reset the colors. Show the bonds that break Show the bonds that form

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Questions:

1) Below is a chart depicting how much chemical potential energy and heat energy molecules have. Determine where ADP-OH, Pi-H, ATP, and H₂O would go in this chart and explain why you put them where you did.

Place the following molecules in the chart to the right: ADP-OH Pi-H ATP H2O Use the reactions above and the idea of chemical vs. heat energy to determine which molecules should be placed over which column.

Explanation of your choices:

 

 

 

 

2) Your body maintains a constant temperature despite the temperature of your surroundings. When standing outside on a cold day, which reaction listed below will help to keep you warm and why?

ADP-OH + P_i-H ---> ATP + H₂O
or
ATP + H₂O ---> ADP-OH + P_i-H

 

 

 

 

 

3) Which chemical bond is stronger the one between ADP and OH or the one between ADP and P_i? How do you know?