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EnzymesLearning objective: to examine what enzymes are anddescribe how they work.
16th October
Enzymes
What are they?
Why do we need them?
Name some examples ?
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
Specific
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
Specific
Increase rate of the reaction
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
Specific
Increase rate of the reaction
Unchanged at the end of the reaction
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
Specific
Increase rate of the reaction
Unchanged at the end of the reaction
Need them
EnzymesGlobular proteins that catalyse chemical reactions in living organisms
Properties
Specific
Increase rate of the reaction
Unchanged at the end of the reaction
Need themReactions too slow to maintain life
Can’t increase temperatures/pressure in cells (fatal)
Enzymes Are ProteinsThe enzyme binds to the substrates by its active site
The active site is a pocket formed by the folding of the proteinwhere the substrates bind.
Enzymes Are ProteinsThe enzyme binds to the substrates by its active site
The active site is a pocket formed by the folding of the proteinwhere the substrates bind.
Active site
The active site involves a small number of key residues that actually bind thesubstrates
The rest of the protein structure is needed to maintain these residues in position
How do enzymes work?
An Example
An Example
Sucrose + H2O
Glucose + Fructose
An Example
Sucrose + H2O
Glucose + Fructose
Substrates
Products
For a reaction to occur the sucroseand water would have to collide with
enough energy to break and form bonds
For a reaction to occur the sucroseand water would have to collide with
enough energy to break and form bonds
This is the activation energy
Sucrose + H2O Glucose + Fructose
++
Substrates Products
Energy
Progress of reaction
Energy
Progress of reaction
Substrates
Energy
Progress of reaction
Substrates Products
Energy
Progress of reaction
Substrates Products
High energy intermediate
Energy
Progress of reaction
Substrates Products
High energy intermediate
Activation energy
The minimum amount of energy needed to start the reaction, leading to the formation of a high
energy intermediate
= The Activation energy
Energy
Progress of reaction
Substrates Products
High energy intermediate
Activation energy
Enzymes reduce the height of the energy
barrier
Questions
1. Write a definition for the following: Active SiteSubstrateProducts
2. Explain how the structure of the protein is linked to its ability to actas an enzyme?
3. How does heating a mixture increase the chance that a chemical reaction Will occur? Why can’t this approach be used in cells?
4. Write a paragraph in your own words describing how enzymes act as catalysts by lowering activation energy.
Read page 57-60
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