Transcript Characteristics of enzymes

What are enzymes made of?
Enzymes are protein molecules, and so are made up
of amino acids.
These amino acids are joined together in a long chain, which
is folded to produce a unique 3D structure.
Why are enzymes so specific in their reactions?
Characteristics of enzymes
• Enzymes speed up chemical reactions
• Enzymes are required in minute amounts
• Enzymes are specific
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Lock and key hypothesis
Enzymes speed up chemical reactions
• Enzymes speed up a chemical reaction by
lowering the activation energy needed to
start the reaction.
Enzymes are required in minute amounts
• Enzymes are very efficient molecules.
• Remain unchanged in the reactions they
catalyse, the same enzyme molecules can
be used over and over again.
Enzymes are specific
• Each chemical reaction inside a cell is
catalysed by a unique enzyme
• Specific due to 3D shape
• Lock and key hypothesis
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Lock and key hypothesis
Enzyme specificity means that each chemical
reaction inside a cell is catalysed by a unique
enzyme.
Why are enzymes so specific?
Enzymes are very specific about which reactions they
catalyze. Only molecules with exactly the right shape will
bind to the enzyme and react.
These are the reactant, or substrate, molecules.
The part of the enzyme to
which the reactant binds is
called the active site.
Active sites
What happens at the active site?
•In the same way that a key fits into a lock, so a substrate
is thought to fit into an enzyme’s active site.
•The enzyme is the lock, and the reactant is the key.
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enzyme
+
substrate
↔
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enzyme-substrate
complex
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↔
enzyme
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products
Lock and key hypothesis
• The substances on which enzymes act are
called substrates.
• Active sites are depressions or ‘pockets’
on the surface of an enzyme molecule into
which the substrate molecule(s) can fitjust like a lock and key.
Effects of temperature on enzyme activity
Optimum temperature for
typical human enzyme
Optimum temperature for
thermophilic bacteria
Effects of pH on enzyme activity
Optimum pH
for pepsin
Optimum pH
for trypsin
Yesterday, Sharon wanted to
make pineapply jelly for her
mother’s birthday.
So, she used fresh pineapple
for the 1st tray and canned
pineapple for the 2nd tray.
However, her jelly using the
fresh pineapple did not set
and was too runny!
What went wrong with her
preparation?
Fresh pineapples could
not set jelly because
of the acids that
digest gelatin.
Probably, she did not put
it in the fridge after
boiling the gelatin.
The presence of fruits
does not affect jelly at
all.
Vivek
Kim
Eve
Canned
pineapple did
not digest
gelatin
because very
few active
enzymes were
present.
What I have learned today?
Mind splatter
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