Enzymes
Enzymes are ____________________. They ____________ the rate of
Metabolic reactions. Almost all Biological Reactions involve Enzymes. All
enzymes are ______________ proteins. They are usually ___________ to
only one reaction.
The part of the Enzyme that acts a Catalyst is called the ______________.
The rest of the Enzyme is much larger and is involved in maintaining the
specific shape of of the Enzyme.
When a reaction involving an Enzyme occurs, a _____________ is turned into
a ____________. The Substrate can be one or more molecules. The Active
Site of an Enzyme is Complementary to the Substrate is catalyses.
Some examples of Enzymes are:
Lactase: Breaks down Lactose into Glucose and Galactose.
Catalase: Breaks Hydrogen Peroxide down into Water and Oxygen.
Glycogen Synthase: Catalyses the formation of Glycosidic Bonds
between Glucose molecules.
ATP-ase: Breaks down ATP into ADP, producing energy.
Enzymes in the Real World
Since Enzymes are Proteins, which are affected by their _______________,
organisms that live in varying conditions have adapted by producing
Enzymes more suitable to their environments. Endotherms (animals that
maintain their body temperature) keep the temperature of the Enzymes
within their bodies constant to ensure optimum rates of reaction.
Enzymes are used for a wide variety of purposes, such as in _____________.
The action of an Enzyme may be _________________ (the Enzymes are
attached to the cell membrane or are in the Cytoplasm, and reactions occur
inside the cell) or __________________ (Enzymes work outside cells, and
their products may be absorbed into the cell)
Enzymes are also used in protection against Pathogens. They can be used to
destroy invading Microorgansims. For example, Phagocytes engulf
Pathogens and the Endocytosed Vesicle then fuses with Lysosomes which
contain enzymes that destroy the Pathogen's cell membrane.
How Enzymes Work
Most reactions in a cell require ___________ temperatures to get going,
which would destroy the cell. Enzymes work by lowering the
__________________ of a reaction.
The Lock-and-key Hypothesis
The Lock-and-key Hypothesis is a model of how Enzymes catalyse
Substrate reactions. It states that the shape of the Active Sites of Enzymes are
exactly Complementary to the ___________ of the Substrate.
The Induced-Fit Hypothesis
A more recent model, which is backed up by evidence and is widely
accepted as describing the way enzymes work is the Induced-Fit
Hypothesis. It states that the shape of Active Sites are not exactly
Complementary, but ___________ in the presence of a specific substrate to
become Complementary.
Competitive Inhibition
In competitive inhibition, a similar-shaped molecule _____________ with the
substrate for active sites.
Noncompetitive Inhibition
Another form of inhibition involves an inhibitor that binds to an _____________
site of an enzyme. An allosteric site is a different location than the active site.
The binding of an inhibitor to the allosteric site alters the shape of the enzyme,
resulting in a distorted active site that does not function properly.