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Higher Human 1.6
1.6- Metabolic Pathways
| Question | Answer |
|---|---|
| What is meant by a Metabolic pathway? | Integrated and controlled pathways of enzyme-catalysed reactions within a cell. |
| Do metabolic pathways all have the same steps? | No – they can have reversible steps, irreversible steps and alternative routes. |
| Name the 2 types of reactions within metabolic pathways | Anabolic or catabolic. |
| What does an anabolic pathway require? | Energy |
| What does an anabolic pathway lead to? | The synthesis of a molecule (build up large molecules from small molecules) |
| What does a catabolic pathway release? | Energy |
| What does a catabolic pathway lead to? | The breakdown of a molecule (break down large molecules into smaller molecules) |
| What are metabolic pathways controlled by? | The presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes. |
| Are genes for some enzymes continually expressed? | Yes |
| Describe what is meant by an induced fit. | When the active site changes shape to better fit the substrate after the substrate binds |
| What is the role of the active site? | Orientate reactants, lower the activation energy of the transition state and the release of products with low affinity for the active site |
| Does the affinity of the substrate / products for the active site differ? | Yes. The substrate molecule(s) have a high affinity for the active site and the subsequent products have a low affinity allowing them to leave the active site. |
| Some metabolic pathways are reversible. What can drive the sequence of reactions in a particular direction? | The presence of a substrate or the removal of a product. |
| What is the effect of increasing enzyme concentration on the rate of a reaction? | The rate of the reaction increases, until all substrate molecules are being acted upon. |
| What is the effect of increasing the substrate concentration? | Increases the rate of the reaction, until all active sites are occupied by substrate. |
| Do enzymes always work independently? | No, they can act in groups or as multi-enzyme complexes. |
| What is an inhibitor? | A substance which reduces the rate of a reaction |
| What is a competitive inhibitor? | An inhibitor which has a similar shape to the substrate. It actively competes for the active site. |
| How does a competitive inhibitor work? | It binds to the active site and blocks it so that it cannot act upon the substrate |
| Can competitive inhibition be reversed? | Yes, by increasing the substrate concentration. |
| How does a non-competitor work? | They bind away from the active site but change the shape of the active site preventing the substrate from binding. (allosteric site) |
| Can Non-competitive inhibition be reversed by increasing substrate concentration? | No, the substrate is not able to bind/ react. |
| Describe feedback inhibition. | Occurs when the end-product in the metabolic pathway reaches a critical concentration. The end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product. |
| What is the benefit of end-product inhibition? | It ensures products do not accumulate and conserves resources. |
Created by:
mackas89
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