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HNC Biochemistry
LO2
| Question | Answer |
|---|---|
| describe what happens in an enzyme catalysed reaction as the concentration of substrate increases. | As the concentration of substrate increases so does the velocity of the reaction. At the point when all the active sites on the available enzyme are occupied the maximum reaction velocity(Vmax) is reached. |
| What are the two types of enzyme inhibitor? | competitive and non competitive |
| Where does the competitive inhibitor bind on the enzyme? | At the active site |
| Where does the non competitive inhibitor bind on the enzyme? | Not on the active site but elsewhere on the enzyme. |
| What is the name for binding to the enzyme that is not to the active site? | Allosteric binding |
| What effect does competitive inhibitor have on Vmax? | Vmax remains the same |
| What effect does non competitive inhibitor have on Vmax? | Vmax decreases |
| What is Km? | Km is the substrate concentration at which enzyme works at half Vmax. It is a measure of affinity of active enzyme for its substrate |
| What effect does competitive inhibitor have onenzyme Km value? | Km increases |
| What effect does a non competitive inhibitor have on enzyme Km value? | Km remains the same |
| What is Vmax? | Vmax is the maximum rate of enzyme activity |
| Why does enzyme Vmax not change in presence of competitive inhibitor? | Given sufficient concentration of substrate competitive inhibitor can be out-competed from the active site. |
| Why does enzyme Km increase in presence of competitive inhibitor? | Concentration of substrate required to achieve half a Vmax increases as competitive inhibitor interferes with substrate binding the active site. |
| Why does enzyme Vmax decrease in presence of non competitive inhibitor? | Non competitive inhibitor binding to the enzyme permanently destroys the enzyme. This effectively reduces enzyme concentration and therefore Vmax. |
| Why does enzyme Km not change in presence of non competitive inhibitor? | Non competitive binding destroys the enzyme. Enzyme not bound to non competitive inhibitor is unchanged, so its affinity for substrate (Km) remains the same |
| How specific is enzyme for its substrate? | Shape of the enzyme active site is perfectly compatible with the shape of the substrate |
| How does enzyme help catalyze chemical reactions? | It reduces activation energy required for chemical reaction to proceed. |
| What is a co-enzyme? | A small organic molecule that helps complex enzymes catalyze chemical reactions. |
| Are co-enzymes true catalysts? | Co-enzymes are not true catalysts as they are spent in the reaction. They have to be regenerated by a different reaction. |
| What is a co-factor? | A metal ion that helps complex enzyme catalyze chemical reactions. It is held in place by the protein part of the enzyme. |
| What is the relationship between Km and enzyme substrate affinity? | Larger the Km value, LOWER the enzymes affinity for substrate |
| What effect does temperature have on enzyme activity? | at low temperatures enzyme works slowly. As temperature rises enzyme works faster until it reaches optimum. If temperature keeps rising past optimum enzyme becomes denatured. |
| What effect does pH have on enzyme activity? | Each enzyme has a narrow range of pH at which it works. Changing pH up or down away from the enzymes optimum denatures the enzyme |
| What does protein denaturation mean? | Denatured protein has altered 3-D shape, and can no longer catalyze chemical reactions |
Created by:
dr.prorocic