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PH level and enzymes
- Thread starter Votorx
- Start date
Ok, first thing to learn about biology is that "Why?" is just about the stupidest question to ask, given that you're going to be given the equally stupid answer of "It just does." As far as how proteins/enzymes are affected by pH, a lot of the amide groups in the chemical structure of proteins (NH2) can pick up an extra proton and become NH3+ groups. In acidic conditions, where there are a lot of extra H+ ions, this "proton pickup" is facilitated. In basic conditions, where there are a lot of OH- ions, the OH- will tend to pull the H+ off of NH3+ groups to reform the NH2 (and a H2O molecule in the process).
As to how this affects the whole protein, almost all of what a protein does is dependent on how it is folded. And how it is folded depends on electrostatic interactions between different chemical groups on the chain of polypeptides in the protein. Say an amide group with an extra proton (NH3+) is interacting with a carboxyl group (COO-) by the "opposites attract" theorem. If you increase the pH, and concentration of OH- ions, the NH3+ will tend to become an NH2 group and the interaction will stop. This will tend to make the protein not hold together as well and thus, with a large number of proteins, increasing the pH outside the normal range will make the proteins not function as well.
-Oh, and by the way, of course this explanation contains a number of very simplifying posits.
As to how this affects the whole protein, almost all of what a protein does is dependent on how it is folded. And how it is folded depends on electrostatic interactions between different chemical groups on the chain of polypeptides in the protein. Say an amide group with an extra proton (NH3+) is interacting with a carboxyl group (COO-) by the "opposites attract" theorem. If you increase the pH, and concentration of OH- ions, the NH3+ will tend to become an NH2 group and the interaction will stop. This will tend to make the protein not hold together as well and thus, with a large number of proteins, increasing the pH outside the normal range will make the proteins not function as well.
-Oh, and by the way, of course this explanation contains a number of very simplifying posits.
By the bazillions, our body builds big molecules out of little ones, and it breaks big ones into little ones. There are ideal temperatures in which these reactions happen. If you get too cold, then these reactions happen slower. If you get too hot, then the molecules sort of unravel and just do not want to cooperate. In the middle, 37 degrees Celsius, or 98.6 Fahrenheit, the temperature is just right and these reactions can go both ways. Enzymes are molecules that tell the other molecules which way to go.Votorx said:On the molecular level, why and how does the ph level effect enzymatic activities?
The ph concentration needs the same sort of balance. If the solution is too acid, meaning that there are too many free protons (H+), then some of the chemical reactions will not take place. If the solution is too alkaline, meaning too many hydroxyl ions (OH-), then again, some of the reactions will not happen.
The enzyme is a biological catalyst. Technically, it lowers the activation energy needed for a reaction. The idea is that before a reaction takes place, you first have to pump some energy into the reactants before they will combine. The act of combining may consume or release energy. It can even release much more energy than the activation energy needed to get it started. However, without first supplying the activation energy, the reaction will not take place. With a catalyst, that enzyme, the reactants do not need as much activation energy, so the reactions happen more often.
The catalyst or enzyme is changed in the reaction, but reverts to its original shape immediately afterwards. The net result is that the enzyme does not change because of the reaction. It just stays the same, ready to speed up another reaction. If the solution containing the enzyme and reactants has the wrong ph, then the enzyme, or the reactants, bind to free protons or hydroxyl ions instead of each other. The result is that the reaction slows or does not happen at all.
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