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Joe Wright
Enzymes
Joe Wright
What are Enzymes?
• Globular proteins
• Biological catalysts
• Do not change after reaction
• They are found in small quantities
• Specific
• Reactions are reversible
Joe Wright
How Enzymes Work
• Enzymes lower the energy required for a chemical reaction to occur (activation energy)
Joe Wright
How Enzymes Work
Joe Wright
Enzyme Structure
• Tertiary Structure of enzyme determines its unique shape.
• Forms its ACTIVE SITE
Active Site
Joe Wright
Enzyme Action
• Enzymes work on specific substrates• Substrate(s) has to fit in the active site• Lock and key hypothesis
Enzyme
Substrate
Enzyme / Substrate Complex
Enzyme unchanged
Products
Active site
Joe Wright
Enzyme Action
• Active site is sometimes flexible
• When substrate(s) enter active site enzyme changes shape
• Induced Fit Theory
Enzyme
Substrates
Active site Enzyme / Substrate
ComplexEnzyme unchanged
Product
Joe Wright
Enzyme Action
• Rate of an enzyme reaction can be affected by:– Temperature– pH– Enzyme Concentration– Substrate Concentration
Joe Wright
Monitoring Enzyme Action
• In an experiment enzyme action can be timed by:
Formation of Products e.g. gas
Disappearance of Substrate e.g. starch
Joe Wright
Enzyme Activity and Temperature
Joe Wright
Enzyme Activity and pH
Joe Wright
Enzyme Activity and Substrate Concentration
Joe Wright
Enzyme Activity and Enzyme Concentration
Joe Wright
What to do now
• Read Key Biological Principle box page 77-79
• Answer Checkpoints 2.3 and 2.4