1. Factors That Affect Enzyme Activity
Class Work
Name: _______________________________ Date: ___________ Block:
_____________
Choose the correct answer to fill in the paragraph that describes
how enzymes work.
Enzymes belong to the (protein, lipid, carbohydrate) group of macromolecules. Enzymes
are biological (catalysts, lipids). These types of molecules (speed up, slow down) the rate
of the chemical reaction without being (used up, involved in) in the reaction. They are
able to do this by lowering the (activation energy, molecular weight, reacting
temperature) of the reactants. The molecule that enzymes work on is called the
(substrate, product). Enzyme reactions depend on the (fit, charge, size) between the
enzyme and its' substrate. The enzyme and the substrate have a specific (shape, charge,
size) that allow them to fit together like a (lock, magnet) and (key, iron). When the
enzyme bonds with the substrate to form the enzyme the enzyme-substrate complex, it
(weakens, strengthens) some chemical bonds in the (substrate, enzyme). This is one way
that enzymes reduce the activation energy. After the reaction, the (enzyme, substrate,
reactant) releases the products. The (enzyme, substrate, reactant) is unchanged by the
reaction and can be used (again, only once). Another model of enzyme action is called
the induced fit model. In this model, the (enzyme, substrate) changes shape slightly when
it comes into contact with the (substrate, product). The rest of the reaction occurs much
as described above. Some factors can affect enzyme activity. One of these factors is
enzyme concentration. If you increase enzyme concentration, the rate of the reaction will
(increase, decrease) up to a certain point and then (decrease, increase, level off). All
molecules have natural motion. If you add more enzymes, these molecules will have a
(greater, lesser) chance of bumping into a substrate molecule and catalyzing the reaction.
The rate levels off because eventually there is not enough (substrate, product) for the
enzymes to find. A second factor that affects enzyme action is substrate concentration. If
you add more substrate, the rate of the reaction will (increase, decrease) up to a certain
point and then (level off, decrease). At first, enzymes run into lots of (substrate, product)

2. molecules because they are plentiful. Eventually all of the (enzyme, substrate) molecules
are being used so the reaction rate levels off. A third factor that affects enzyme action is
temperature. If you increase the temperature, the rate of reaction (increases, decreases)
until it gets too hot and then the rate will (decrease, increase). An increase in temperature
causes the molecules to move (faster, slower). As they move (faster, slower), the
enzymes are more likely to bump into the (substrate, product) and catalyze the reaction.
At very low temperatures the enzymes move (slowly, quickly). Thus they do not bump
into the (substrate, product) as often and the rate of the reaction (decreases, increases). If
the temperature gets too high, this causes the protein structure to (break down, double in
size, decrease in size) or denature which means that it changes (shape, order). The
enzyme no longer fits the (substrate, product) exactly so the reaction (will not, will)
occur. A final factor that affects enzyme action is pH. This scale measures how acidic
and basic something is. If a substance has a pH of (0-6, 7, 8-14) it is considered an acid.
If a substance has a pH of (8-14, 7, 0-6) it is considered a base. Water, which is
considered (neutral, acidic, basic) has a pH of (7, 0-6, 8-14). All enzymes have specific
pH ranges that they work best in. Putting an enzyme in an acidic or basic pH, if it works
best at neutral pHs, causes the enzyme to (change shape, double in size, decrease in size)
or denature. When this happens the enzyme no longer fits the (substrate, product) exactly
so the reaction (will not, will) occur.