Enzymes
- Created by: farahh24
- Created on: 10-09-18 19:37
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- Enzymes
- Factors affecting enzyme reaction rates
- Temperature
- Increased temperature
- Increased kinetic energy
- Increased movement of substrate and enzymes
- Greater chance of collision, greater rate of reaction
- Increased movement of substrate and enzymes
- Increased kinetic energy
- Temperatures that are too high can break the bonds in the tertiary structure of the enzyme
- This changes the shape of the active site, making it no longer specific to the substrate
- Increased temperature
- pH
- A change in the amount of hydrogen ions available causes the tertiary structure to change
- This is because there are hydrogen bonds in the tertiary structure that may alter in the presence of more hydrogen ions
- This changes the shape of the active site, making it no longer specific to the substrate
- This is because there are hydrogen bonds in the tertiary structure that may alter in the presence of more hydrogen ions
- A change in the amount of hydrogen ions available causes the tertiary structure to change
- Substrate and enzyme concentration
- Greater number of substrates, increased likelihood of collision with enzymes, increased rate of reaction
- Greater number of enzymes, increased available active sites, greater likelihood of collision, increased rate of reaction
- Temperature
- Competitive inhibition
- A molecule or part of a molecule that is the same shape as the substrate attaches to active site of enzymes.
- This reduces the availability of active sites for the substrate, and reduces the rate of reaction.
- A molecule or part of a molecule that is the same shape as the substrate attaches to active site of enzymes.
- Non-competitive inhibition
- Inhibitor binds to allosteric site.
- This changes the tertiary structure and the active site changes shape. This means it is no longer specific to the substrate, and the enzyme is inhibited.
- Example of a irreversible non-competitive inhibitor
- PPIs - proton pump inhibitors, used to treat long term indigestion. Irreversibly block enzymes responsible for secreting hydrogen ions into stomach. This reduces the amount of hydrochloric acid in the stomach
- Can be reversible or irreversible
- Inhibitor binds to allosteric site.
- End-product inhibition
- Product of a reaction acts as an inhibitor to enzyme that produced it.
- Negative feedback
- E.g. in respiration, ATP is produced. When ATP levels are high, more ATP binds to the allosteric site on the PFK enzyme, preventing addditin of second phosphate group to lcuose
- Product of a reaction acts as an inhibitor to enzyme that produced it.
- Co-factors
- Non-protein 'helper' component. Inorganic.
- Inorganic: obtained through diet, calcium, iron, etc.
- Amylase - catalyses breakdown of starch - requires cofactor of chloride.
- Inorganic: obtained through diet, calcium, iron, etc.
- Non-protein 'helper' component. Inorganic.
- Coenzymes
- Non-protein 'helper' component. Organic. Derived from vitamins.
- Vitamin B3 used to synthesise NAD coenzyme. This coenzyme is required for alcohol dehydrogenase to break down ethanol.
- Non-protein 'helper' component. Organic. Derived from vitamins.
- Prosthetic groups
- Precursor activation
- Many enzymes produced in inactive form, especially with enzymes that may harm the cell producing them.
- Pepsinogen - originally inactive, the low pH activates enzyme.
- Many enzymes produced in inactive form, especially with enzymes that may harm the cell producing them.
- Factors affecting enzyme reaction rates
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