SR.BIOCHEM.3A
BIOLOGY CURRICULUM 2006
ENZYMES – YOU CAN’T LIVE WITHOUT THEM!
Background Information
All living things have mechanisms that allow them to maintain a stable internal
environment. Without these mechanisms organisms can die. The maintenance of internal
conditions is known as homeostasis. Organisms have regulatory systems that maintain internal
conditions, a large part of which are enzymes that reduce the amount of energy needed by cells
for chemical reactions to take place. Without the aid of enzymes, chemical reactions would
occur too slowly to sustain life.
Enzymes are a class of proteins, which are able to aid in the completion of chemical
reactions. Enzymes are known as catalysts. Catalysts increase the rate of chemical reactions.
Without them, reactions would occur very slowly. Enzymes are highly specific in their catalytic
activity, meaning that certain enzymes work with certain substrates. The reason they are so
specific is because the enzyme and substrate fit closely together. The three-dimensional fit of the
enzyme-substrate complex helps chemical reactions occur by lowering the energy needed to
complete the joining or breaking of the substrate to make the desired product. Once the chemical
reaction is complete, the enzyme and substrate separate. The substrate has changed during the
reaction, but the enzyme remains the same allowing it to react with another substrate until all the
substrate has been changed into the desired product.
Enzymes are very sensitive proteins and can be affected by changes in
temperature and pH. An enzyme’s three-dimensional shape is the result of weak
bonds between amino acids. The weak bonds cause folding and twisting of the amino
acid chain that makes up the enzyme. These weak bonds can be broken by changes
in pH and temperature. Under harsh conditions such as extreme temperatures or
pH levels, enzyme becomes denatured, or inactive. Once denaturing occurs and
the shape of the enzyme changes, it is no longer able to fit together with its substrate and its
catalytic function is lost. Depending on its location in the body, each enzyme has an optimum
pH and optimum temperature at which it works best.
Vocabulary Check: Using the reading from above, define each of the following words.
Homeostasis –
Enzyme –
Catalyst –
Substrate –
Denatured –
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SR.BIOCHEM.3A
BIOLOGY CURRICULUM 2006
Enzymes are in your Saliva!
Starches are complex carbohydrates that are found in food such as rice,
potatoes, bread and crackers. Digestion of carbohydrates, such as starches,
begins in your mouth when it mixes with your saliva. The digestive
process is completed in the small intestine. Amylase is an enzyme found in
saliva that breaks down starches into simple sugars. (Just as with amylase,
most enzymes end in the suffix “ase”). Amylase is a catalyst, because it
causes a chemical reaction to take place quickly without being changed by the
reaction. That very same enzyme will do the same thing the next time a starchy
food is eaten. Without enzymes such as amylase, our metabolism would occur too slowly to
sustain life.
Check your Understanding: Using the information above, answer the following questions.
1. What type of macromolecules are enzymes?
2. Enzymes are catalysts. What does this mean?
3. The amylase enzyme found in _________________________ breaks
_________________________ down into _________________________.
4. What can cause an enzyme to become denatured?
5. How could our metabolism be affected if there were no enzymes?
252
SR.BIOCHEM.3A
BIOLOGY CURRICULUM 2006
Demonstration
Using indicators, you will observe the effect of the enzyme amylase on the starch in a
cracker. Iodine is an indicator that turns dark blue in the presence of starch and glucose test
strips change color in the presence of sugar. Fill in the chart below as instructed by your teacher.
Color of iodine: __________________________________
Color of glucose test strip: _________________________
Beaker A
(Cracker + saliva)
Beaker B
(Cracker + water)
Reaction to iodine
Reaction to
glucose test strip
Answer in complete sentences.
1. What does the data suggest about the action of enzymes in your body?
2. What temperature and pH does amylase work best at?
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