Chemical Reactions

Cornell Notes

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Metabolism An incredibly large

number of chemical reactions happen in your body every second of your life.

Metabolism is a term used to describe all of the chemical reactions in a person’s body.

Reactants and Products

In chemical reactions, molecules are changed in some way. The beginning molecule(s) are the reactants and the resulting molecule(s) are the products.

R E A C T A N T S P R O D U C T S

This is an example of a chemical reaction:

H2O2 H2O + O2

 

Hydrogen is broken down Water and Oxygen

Peroxide in your cells into

R E A C T A N T S P R O D U C T S

Hydrogen peroxide is made in your cells all the time. However, it is toxic if it is not quickly broken down into water and oxygen, which are not toxic.

Chemical reactions don’t happen spontaneously though. Every chemical reaction requires a certain amount of energy in order for it to happen.

For a chemical reaction to take place, it has to “get over the hump,” as far as energy is concerned.

The amount of energy a chemical reaction requires is called its activation energy. A chemical reaction will not occur until it has this amount of energy. The activation energy corresponds to the top of the “hump” on the graph.

Label graph

The activation energy of most chemical reactions is too high for them to happen on their own. Luckily your body has enzymes to help.

Enzymes are proteins your body has that work by binding to a specific molecule and lowering its activation energy. The graph below represents the chemical reaction from above with an enzyme lowering its activation energy:

The “hump,” or activation energy, has been lowered so not as much energy is required for it to occur.

For example, your body has an enzyme called catalase that helps the cells break down hydrogen peroxide so it doesn’t poison you.

CATALASE

+

When the activation energy is lowered, the chemical reaction happens much faster. Another word for an enzyme is a catalyst.

A catalyst speeds something up (enzymes speed up chemical reactions).