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14 Cards in this Set
- Front
- Back
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Definition of an Enzyme |
Enzymes catalyses reactions that affect metabolism at both a cellular and whole organism level. |
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Enzymes in Reactions |
Anabolic: Chemical reactions where simple molecules are combined to form more complex molecules. Catabolic: Chemical reactions where complex molecules are broken down to form more simple molecules. |
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Enzymes in Reactions |
Catalase: Hydrogen peroxide = Water + Oxygen (intracellularly) Trypsin: Breaks down protein (extracellularly) Amylase: Hydrolyses starch into sugars. (extracellularly) |
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How enzymes work |
They need to successfully collide and that requires: Activation energy Correct Orientation |
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Lock and Key Hypothesis |
Within the tertiary structure of an enzyme is a shape that compliementary to shape of a specific substrate molecule. This area is called the active site |
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Lock and Key Hypothesis |
A large substrate molecule is split into smaller product molecules that are then released from the active site. Two smaller substrate molecules attach to the active site and bonds form between them, making a larger product molecule. The enzyme is able to form a ES complex (enzyme-substrate complex) with another substrate molecule and catalyse another reaction. |
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Induced-Fit Hypothesis |
The intial interaction between the enzyme and substrate is relatively weak, but these weak interactions rapidly induce changes in the enzyme's tertiary structure that strengthen binding, putting strain on the substrate molecule. This can weaken a particular bond, or bonds, in the substrate therefore lowering the activation energy for the reaction. |
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Factors Affecting Enzyme Activity |
pH Temperature Enzyme Concentration Substrate Concentration |
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pH |
pH is a measure of the Hydrogen ion concentration. H ions carry + charge so are attracted towards - charged ions, also will be repelled by positively charged areas. H ions interfere with the H bonds and ionic bonds holding the tertiary structure in place so a change in pH can cause changes to the active site so can change the rate of an enzyme-controlled reaction. All enzymes have their own optimum pH. |
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Temperature
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Optimum temperature Increase temp, increases kinetic energy, increases number of collisions between substrate and active sites. Above optimum temp, leads to denaturation, H and disulphide bonds are broken and they maintain active site. |
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Substrate Concentration |
At low S.C. slow rate of reaction, not enough substrate molecules. As S.C. increases the rate increases until a certain point as all active sites will be occupied. |
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Enzyme Concentration
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At low E.C. more substrate than active sites. Increase no. of active sites by increasing E.C. increases rate of reaction. At a certain point, increasing E.C. has no affect on reaction rate as S.C. is limiting factor. |
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Q10 |
Q10 is the measure of the rate of change of a reaction when the temperature is increased by 10 degrees Celsius. Q10 = Rate of reaction at (x+10) / Rate of reaction at x |
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Q10
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Many enzymes have a Q10 of between 2 and 3. An increase in temperature by 10C will speed up reaction by a factor of 2-3 |
