Enzymes
- Created by: ebcrankomills
- Created on: 23-05-19 11:16
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- Enzymes
- Mechanism of Enzyme action
- Induced Fit
- Active site changes shape slightly when the substrate enters
- initial interaction between enzyme and substrate is week
- Interactions rapidly induce changes in the enzymes tertiary structure
- This can weaken a bond which will lower the Ea of the reaction
- Lock and Key
- Enzyme and substrate are complimentary in shape
- Enzyme- substrate complex formed when substrate binds to active site
- Enzyme-product complex formed after the substrate has reacted
- R-groups of the active site will also interact with the substrate
- Induced Fit
- Intracellular enzymes
- Hydrogen Peroxide is a toxic product of many metabolic pathways.
- Catalase ensures that it is broken down into oxygen and water quickly
- Hydrogen Peroxide is a toxic product of many metabolic pathways.
- Extracellular Enzymes
- they can be used to break down polymers for nutritional purposes
- this is done through digestion
- Multicellular organisms need enzymes to digest and break down food
- examples are: amylase and trypsin
- Unicellular organisms need enzymes to break down larger molecules so that they can be absorbed
- they can be used to break down polymers for nutritional purposes
- Factors affecting enzymes
- Temperature
- Temperature coefficient Q10
- Increasing the temperature of a reaction increases the kinetic energy of the particles
- Denaturation- As temperature increases vibrations increase untuk the bonds strain and break completely.
- this changes the tertiary structure of the protein. It is denatured.
- Most bodily enzymes have an optimum temperature of around 40 degress.
- Thermophilic bacteria have enzymes with much higher optimum temperatures
- Psychrophilic organisms have enzymes with much lower optimum temperatures.
- pH
- The active site will only be the right shape at certain H+ concentration
- Substrate and Enzyme concentration
- Increasing the concentration of substrate, increases the collision frequency. More enzyme-substrate complexes are formed. The rate of reaction is faster
- The same thing happens when the concentration of the enzyme increases
- Rate will continue to increase up to its Vmax.
- Increasing the concentration of substrate, increases the collision frequency. More enzyme-substrate complexes are formed. The rate of reaction is faster
- Temperature
- Inhibition
- Competitive
- Inhibitor binds to the Active Site
- Inhibitor is of similar shape to the substrate
- Blocks substrate from entering the active site, prevents it catalysing the reaction
- Reduces rate of reaction but does not change the Vmax.
- Example: Statins are competitive inhibitors of cholesterol synthetics and are often prescribed to help reduce blood cholesterol levels
- Non-competitive
- Inhibitor binds to the allosteric sight
- Causes the tertiary structure of the active sight to change, so its shape changes
- Active site is no longer complimentary to substrate
- Increasing the concentration of enzyme or substrate won't overcome its effect. Increasing the concentration of the inhibitor will further decrease the rate of reaction
- Example: Organo-phosphates used as insecticides and herbicides irreversibly inhibit acetyl cholinesterase responsible for nervous transmission
- End-product
- The product of a reaction acts as n=an inhibitor for the enzyme that made it
- Example of negative feedback
- Competitive
- Cofactors and Coenzymes
- Cofactors = non-protein 'helper,' components.
- Coenzyme = A cofactor which is an organic molecule
- Prosthetic groups are cofactors, they are required by certain enzymes to carry out their catalytic function.
- Precursor Activation
- precursor enzymes need to undergo a change in shape to be activated. the addition of a cofactor can do this
- Before the cofactor is added the precursor protein is called an apoenzyme
- After the cofactor is added it is called a holoenzyme
- precursor enzymes need to undergo a change in shape to be activated. the addition of a cofactor can do this
- Mechanism of Enzyme action
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