Enzymes
Higher Human Biology
Lesson Aims
• To revise purpose of enzymes
• To revise how enzymes work
• To examine factor affecting rate of enzymecatalysed reactions
Enzymes video clip
Structure
• Globular proteins
• One or more polypeptide
chains
• Function determined by
structure
• Reaction occurs at active site
• Specific for one reaction due
to shape of active site – “lock
and key” hypothesis
amylase
Function
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•
•
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Biological catalysts - increase reaction rates
Approx 40,000 different types in human cells
Intracellular (inside cell) e.g. catalase
Extra-cellular (outside cell) e.g. pepsin
Needed for respiration, photosynthesis,
digestion, motors, membrane pumps, receptors
Reaction Mechanism
Inborn errors of metabolism
• Metabolism – all the
chemical reactions
that occur in an
organism
• Error in gene coding
for enzyme results in
blockage in pathway
• May result in health
problems
Factors Affecting Enzyme Activity
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pH
Temperature
Enzyme concentration
Substrate concentration
pH
Temperature
Enzyme Concentration
Substrate Concentration
Activation of Enzymes
• Cofactors (coenzymes) required
• metal ions – iron (Fe2+), magnesium
(Mg2+), copper (Cu2+)
• organic molecules e.g. haem, NAD,
coenzyme A
Inhibition
• Substrate can’t fit into
active site of enzyme
• Reaction rate lowered
2 types:
• Competitive
• Non-competitive
The Facts You Need To Know
• page 1
• from “enzymes are biological catalysts….”
• to “e.g. iron in catalase…”
Outcome 3
• Assessed practical
• “Effect of enzyme concentration
enzyme action”
• Submit write-up by:- Mon 28th June
on