I'm kinda confused about the size of the active site of enzymes. Enzymes are proteins made up of thousands of amino acids right? So how do they catalyze reactions with reactants that are much, much smaller than they are (example: hydrogen peroxide, how does Catalase catalyze the decomposition of hydrogen peroxide when hydrogen peroxide is really small compared to itself)? Is the active site really small or something? Can it fit multiple molecules?
Also my textbook says altering the pH level of the solution surrounding an enzyme can denature the enzyme and substrate. Doesn't that imply that substrates can be proteins? But why would a protein need to bind to an enzyme if the role of an enzyme is to speed up chemical reactions?
I'm afraid I don't know enough to comment on the size of an active site. However, most models I've seen (example below) show the enzyme as being significantly larger than the substrate, so I assume they are quite small. I'll wait for somebody else to comment on this.
You are correct. Substrates can indeed be proteins. Proteins can undergo reactions too. It's a bit hard to explain without an example, so I'll use one. When some animals (typically young ruminants like sheep) drink liquid milk, they need it to form into a solid (coagulation), because if it's a liquid it'll leave the body too quickly and thus not allow the nutrients to be absorbed. If it's more of a solid, it'll pass slowly through the body. The digestive acids in the stomach will coagulate this, but it'll do it rather slowly, so it needs to speed up the process. This is where an enzyme dedicated to a specific protein (these are called 'proteases'. Enzymes for carbs are called carbohydrases and enzymes for lipids are called lipases) called 'chymosin'. The chymosin speeds up the reaction and converts the liquid milk to a solid, called curd.
The protein needs to undergo a chemical reaction. The enzyme is there to do that.
god i hope that make sense i'm horrid at this
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