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Enzyme Regulation
Bio 2 Lecture 6
| Question | Answer |
|---|---|
| What does enzyme rate reactions reveal? | Affinity (Km) for the substrate, the condition of the protein (enzyme shape), the enzyme saturation and the presence of an inhibitor |
| How does enzymes work? | The action of an enzyme fundamentally relies on its ability to bind to its substrate, this occurs through molecular collisions |
| What is binding affinity? | It's a measure of how strong the non-covalent bonds of 2 molecules is |
| What happens when there's a higher affinity (enzyme kinetics)? | Higher affinity means less substrate is needed to saturate the enzyme. |
| Why is less substrate needed when their's higher affinity? | Bc the binding is more efficient |
| What does Km represent? How do we read it? | It measures the affinity of an enzyme has for the substrate. The smaller the Km, the higher the affinity. |
| What does a low Km mean? | It means that it has a bigger affinity, meaning that only a small amount of sustrate will be required to saturate. |
| What does Vmax represent in term of enzyme? | Maximum velocity (Vmax ) represents the maximum rate the enzyme is capable of working to convert substrate to product, and occurs when the reaches saturation by substrate |
| Know how to interpret a Binding affinity graph with Vm and substrate concentration | slide 2? |
| What is the mathematical definition of Km? | Concentration of substrate= 1/2 Vmax |
| What are the 2 regulating mechanisms? | There's negative feedback inhibition and allosteric regulation |
| What is negative feedback inhibition? | Known as inhibitory loop, it's a type of self-regulating system. Increased output from system inhibits future production by system. Ex: The body reduces amount of certain proteins/hormones it creates when the levels get too high |
| What is allosteric regulation? | It's the speeding up or slowing down of enzyme activity to ensure that pathways produce just what is needed at that moment (not more than needed) |
| What are the variables of a metabolic pathways? | 1)Initial substrate: It starts the pathway 2)Intermediates: in between initial substrate and final product 3)End-product: the product of the last conversion in a pathway. |
| In what way does feedback inhibition regulates a pathway? Consider the initial substrate, the end-product and enzyme 1 | In negative feedback control, the end-product and initial substrate have a similar structure thus both recognize the enzyme (E1). But EP blocks E1. See slide 10 for visual representation |
| Does the shape of end-product resemble the initial substrate? | sì |
| What are the 3 characteristics of inhibitors? | 1) Inhibitors resemble an earlier substrate 2)Inhibitor may either slow down the enzyme or block it altogether 3)Inhibition must be reversible |
| It slows the pathway down, so what kinda effect does it have? | a negative effect :) |
| What are the 2 ways an enzyme can bin inhibitors? | 1) Competitive inhibitors 2)Noncompetitive inhibitors |
| How does competitive ihibitors work? | Competitive inhibitors block the active site so the substrate can't bind, which decreases the affinity. |
| How does noncompetitive ihibitors work? | Noncompetitive binds to the allosteric site (site other than active site), which changes the shape of the enzyme. When the allosteric site is bound by an inhibitor, the active site will still bind the normal substrate but cannot convert the product as |
| How can the effect of a competitive inhibitor be reduced? | Because the inhibitor is in competition with the substrate, a higher substrate concentration can reduce the effects of the inhibitor. |
| What are the effects of competitive inhibition on Km? | Km (affinity) changes (but Vmax stays the same). |
| Why must competitive inhibition be reversible? | To regulate pathway, the controlling enzyme must be able to slow down or to speed up the pathway. If the regulating molecule binds to the active site irreversibly, then that enzyme can no longer be used. In critical pathways, that could kill an organism |
| Why doesn't the Vmax get affected by competitive inhibition? | If the substrate binds to the active site, the enzyme functions normally thus the rate it converts S to P is unaffected. Aka, Vmax is calculated once the inhibitor is gone and it's the substrate that is binded to the active site! |
| Recognize a graph showcasing competitive enzyme inhibition | Basically, the graph will show 2 curves. One will look steeper than the other, bc it'll have a higher Km (inhibited!). However, you'll observe that the Vm is the same for both slopes. |
| Why does the Vmax changes with noncompetitive inhibition? | We know the Km doesn't change, so the affinity is untouched. The enzyme has the same attraction for the active site, but the enzyme takes longer to convert substrate to product due to the shape change of the enzyme. The Vmax decreases! |
| Recognize a graph showcasing noncompetitive enzyme inhibition | You'll see the km are the same, but the Vm aren't. This is showcased by putting the slope of the inhibited enzyme lower than the normal one. |
| What happens to the enzyme when a molecule binds to the allosteric site? | The shape of the ACTIVE SITE changes! so the properties/affinity of the protein changes |
| Allosteric enzymes can be .... or .... | incativated or activated |
| What are the 2 types of allosteric enzymes? | There's allosteric inhibitors and allosteric activators |
| What do allosteric inhibitors do? | Allosteric inhibitors bind to the allosteric site to inactivate the enzyme |
| What do allosteric activators do? | Allosteric activators bind to the allosteric site to activate the enzyme |
| You can compare allosteric regulation to a light switch bc ... | allosteric regulation can turn a reaction on or off |
| Recognize allosteric inhibition | wth slide 25 ? |
| [Recap] Where does the competitive inhibitor binds? Where does the non-competitive inhibitor bind? | Competitive binds at active site. Non-competitive binds away from active site (allosteric site) |
| [Recap] Are inhibitors similar in structure to the substrate for competitive and non-competitive inhibitors? | Competitive is similar in structure to substrate. Non-competitive has different structure to substrate. |
| [Recap] What happens to Vmax for competitive and non-competitive? | Unchanged for competitive and lowered for non-competitive. |
| [Recap] What happens to Km for competitive and non-competitive? | Increased for competitive and unchanged for con-competitive. |
| [Recap] Does substrate concentration have an effect on competitive and non-competitive? | Increasing the [substrate] has an effect on competitive but no effect on non-competitive. |
| How do enzymes help control metabolic pathways? | Using processes like feedback regulation; competitive and non-competitive inhibition you can control the pathway and when/how much product is produced (or just stop the production lol) |
Created by:
Malayka
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