Enzymes
Chapter 2: Section 2.5
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Objectives
• SWBAT explain the effect of a catalyst on
activation energy.
• SWBAT describe how enzymes regulate
chemical reactions and maintain homeostasis.
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Vocabulary
• Catalyst
• Enzyme
• Substrate
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Starter: How can this be possible
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Catalyst
• A catalyst lowers activation energy.
• Catalysts are substances that speed up chemical reactions.
– decrease activation energy
– increase reaction rate (speed up reactions).
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Enzymes are catalysts in living things
• Enzymes allow chemical reactions to occur
under tightly controlled conditions.
– Like inside of a cell or intercellular space.
• Enzymes are catalysts in living things.
– Enzymes are needed for almost all processes.
– Enzymes are proteins.
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Detailed Definition Enzymes
• UC Davis Site:
http://chemwiki.ucdavis.edu/Biological_Chem
istry/Catalysts
• When we think about information and its
reliability, the source is important. If you
would like to read in detail about enzymes (at
a college level) check out this website.
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Point of Review
•
•
•
•
•
•
Enzymes are proteins.
Proteins are what kind of Molecule?
Answer: a carbon-based molecule.
Proteins are made up of what?
Answer: they are made up of amino acids.
Proteins are polymers of amino acids (making
amino acids monomers).
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Reactions with and without enzyme
Substrate
refers to
your
reactants
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Reactions without Enzymes
• Chemical reactions in biological systems would
occur very slowly if at all without enzymes.
• Enzymes are essential for maintaining
homeostasis.
– Homeostasis is the equilibrium that exists among
all of the physiological processes occurring in a
living organism at any given time.
– When homeostasis is compromised, the organism
is unwell – Ex. viruses can disrupt homeostasis.
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An enzyme’s function depends on its structure.
• An enzyme’s structure allows only certain reactants to bind to
the enzyme.
substrates
(reactants)
– substrates
– active site
enzyme
Substrates bind to an
enzyme at certain places called
active sites.
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An enzyme’s function depends on its
structure.
• The lock-and-key model helps illustrate how enzymes
function.
– substrates brought together
– bonds in substrates weakened
Substrates bind to an
enzyme at certain places
called active sites.
The enzyme brings
substrates together and
weakens their bonds.
The catalyzed reaction forms
a product that is released
from the enzyme.
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Example of Enzyme and Substrate
• Enzyme + Reactant
Product + Enzyme
• Example: Starch (carbohydrate + Amylase
Maltose (C12H22O11) + Amylase
– NOTE: The amylase, being an enzyme, is never
used up. It catalyzes the reaction.
• In your large intestine, maltose is further
broken down by amylase into glucose.
– Amylase + Maltose
Glucose + Amylase.
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Examples
• Protease + Protein
Amino Acids +
Protease.
• Lipase + Lipids
Fatty Acids + Lipase
• Again NOTE: The enzymes are not consumed
by the chemical reactions. They catalyze
them!
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Examples of Enzymes
• Tryptophan hydroxylase (an enzyme) takes
tryptophan (the substrate) and facilitates the
synthesis of serotonin.
– Serotonin is a steroid that is a neurotransmitter (a
chemical substance that transmits nerve impulses
across synapses).
– It is involved in mood, appetite, sleep, memory,
learning and depression (upping levels tends to
relieve depression).
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