What Causes Enzyme Activity to Slow Down?

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Enzymes are susceptible to a number of different types of changes in the cell. Find out what causes enzyme activity to slow down with help from an experienced chemistry professional in this free video clip.

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Hi, I'm Dan Weisenberger and this is what causes enzyme activity to slow down. Enzymes are susceptible to a number of different types of changes in the cell. I've shown four of them here, temperature, substrate concentration, pH and the enzyme concentration itself. So let's go up to temperature. At very low temperatures, enzyme activity is slow and as we go up to exceedingly high temperatures, the protein will denature the program can then not assume its three dimensional shape and function and activity drops. As we increase substrate, we also see an increase in activity, however, at very high concentrations, the activity begins to level off. At pH which is a measure of acidity of a cell, at very low pH levels which are essentially very basic, the enzyme rate of catalysis goes down as we increase pH up into about 7.5 we get an optimal activity and then as we get to higher and higher pH levels the activity drops. And finally the activity of the enzyme is also affected by the enzyme itself or its concentration in the cell. If we look at a 0 order kinetics, it should be a 1 to 1 in which as the enzyme concentration increases, its activity goes up but in more real world examples it does tail off as we have saturated the substrate needed to convert a chemical reaction. There are some other items that could affect enzyme activity, the presence of inhibitors which if those are in proximity of the enzyme will cause it to not be able to do its job, modifications and these include phosphorylation, glycosylation, things like this that could potentially modulate the structure of the enzyme and therefore change its function. Finally, well there are two more things, one is if the enzyme needs a coenzyme, if there is no coenzyme, then the enzyme cannot function. And finally, proteins do have allosteric binding sites in which this is where a ligand binds a part of the enzyme that is outside of its active site and may change confirmation of that enzyme. If these things happen, the confirmation may affect the enzyme's active site being accessible to substrate and being able to convert that into product. I'm Dan Weisenberger and this is what changes enzyme function in cells.

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