3.28. Catalysts http://www.ck12.org
http://www.scs.sk.ca/cyber/elem/learningcommunity/sciences/chemistry30/curr_content/chem30/modules/module4/l
esson5/explainingcatalysts.htm
FIGURE 3.43
Q:In theFigure3.43, look at the energy needed in the catalytic and non-catalytic pathways of the reaction. How
does the amount of energy compare? How does this affect the reaction rate along each pathway?
A:The catalytic pathway of the reaction requires far less energy. Therefore, the reaction will occur faster by this
pathway because more reactants will have enough energy to react.
Catalysts in Living Things
Chemical reactions constantly occur inside living things. Many of these reactions require catalysts so they will occur
quickly enough to support life. Catalysts in living things are called enzymes. Enzymes may be extremely effective.
A reaction that takes a split second to occur with an enzyme might take many years without it!
More than 1000 different enzymes are necessary for human life. Many enzymes are needed for the digestion of food.
An example is amylase, which is found in the mouth and small intestine. Amylase catalyzes the breakdown of starch
to sugar. You can see how it affects the rate of starch digestion in theFigure3.44.
Q:If you chew a starchy food such as a soda cracker for a couple of minutes, you may notice that it starts to taste
slightly sweet. Why does this happen?
A:The starches in the cracker start to break down to sugars with the help of the enzyme amylase. Try this yourself
and see if you can taste the reaction.
Summary
- A catalyst is a substance that increases the rate of a chemical reaction.
- A catalyst provides an alternate pathway for the reaction that has a lower activation energy. When activation
energy is lower, more reactant particles have enough energy to react, so the reaction occurs faster. - Chemical reactions constantly occur inside living things, and many of them require catalysts to occur quickly
enough to support life. Catalysts in living things are called enzymes.