enzymes
Post on 23-Feb-2016
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Enzymes
What are they?
Organic/Biological CatalystsProteinsReusableThere’s over 40,000 found in humansUsually end in the suffix –aseNamed after what it “eats” (ex: if an enzyme is meant to eat lactose the enzyme is lactase)
How do they work?
Enzymes possess an active site (which is like a cleft in the molecule)The active site is where its food (substrate) goes intoWhen the substrate binds to the enzyme it is called an enzyme substrate complex
A new substrate will then be synthesized (created) or the old one will be splitEnzymes DO NOT change in the process
Reactions
Enzymes CANNOT create reactions they only speed them up
Enzymes speed up reactions by lowering the activation energy (energy needed to get the reaction to take place)There are two parts to a chemical reaction: reactants (what goes in) and products (what comes out)Example: Carbonic anhydrase is an enzyme found in RBCs where it catalyzes the reaction CO2 + H2O ↔ H+ + HCO3
− this allows blood to transport CO2 from the tissues to the lungs (one molecule of this enzyme can process one million molecules of CO2 each second
Synthesis Reaction
Active site
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
Molecule GeometrySubstrate molecule fits into the enzyme like a lock & key.Enzyme shape distorts or changes other factors to make the reaction happenHowever certain substances canbind to the enzyme at sites other than the active site and modify its activity (inhibitors/co-factors)Idea that the enzyme is flexible (induced fit)
Activation Energy
In a ‘natural’ reaction the product has a lower energy than the substrate so equilibrium will take it in the direction of the product.However there is an energy ‘barrier’ to be overcomeEnzymes lower the activation energy required to bring about a reaction.Activation energy- the minimum amount of energy needed to start a reaction
Energy
Progress of reaction
Substrates Products
High energy intermediate
Activation energy
Enzyme activity
Four Variables
Temperature
pH
Enzyme Concentration
Substrate Concentration
Optimum ConditionEnzymes function best or are most active in specific
conditions known as optimum
conditions.
Rat
e of
Rea
ctio
n
Temperature
0 20 30 5010 40 60
40oC - denatures
5- 40oC Increase in Activity
<5oC - inactive
Rat
e of
Rea
ctio
n
pH
1 3 42 5 6 7 8 9
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at activesite
Rat
e of
Rea
ctio
n
Enzyme Concentration
Enzyme Concentration
Rat
e of
Rea
ctio
n
Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover
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