Temperature: That's a good one. Proteins change shape as temperatures change. Because so much of an enzyme's activity is based on its shape, temperature changes can mess up the process and the enzyme won't work. High enough temperatures will cause the enzyme to denature and have its structure start to break up. Activators: Sometimes you need an enzyme to work faster. Your body can then create activators. At other times, you might eat something that plays the role of an activator. Activators make enzymes work harder and faster. If you're running in a race and you need more energy, get those enzymes to work! Hormones can trigger responses that activate enzymes.
Inhibitors: These are the opposite of activators. Inhibitors either slow down or stop the activity of an enzyme. They often bond to the protein, changing the overall shape of the enzyme. Remember, when the shape changes, the enzyme will not work the same way. A nasty example of an inhibitor is snake venom or maybe nerve gas from World War I.
Enzyme Molecules as Nanomotors (American Chem Society Video)
The pH scale is used to measure the acidity or alkalinity of a sample and describes how many hydrogen ions or hydroxides are present in the sample. The change of pH will lead to the ionization of amino acids atoms and molecules, change the shape and structure of proteins, thus damaging the function of proteins. Enzymes are also proteins, which are also affected by changes in pH. Very high or very low pH will lead to the complete loss of the activity of most enzymes. The pH value at which the enzyme is most active is called the optimal pH value.
pH Effects Enzyme Activity The structure of the enzyme has a great influence on the activity of the enzyme. In other words, changes in the structure of the enzyme affect the rate of chemical reactions. When the pH value of the reaction medium changes, the shape and structure of the enzyme will change. For example, pH can affect the ionization state of acidic or basic amino acids. There are carboxyl functional groups on the side chain of acidic amino acids. There are amine-containing functional groups in the side chain of basic amino acids. If the ionized state of amino acids in the protein is changed, the ionic bonds that maintain the three-dimensional shape of the protein will change. This may lead to changes in protein function or inactivation of enzymes. pH Effects Substrates PH not only affects the activity of the enzyme, but also affects the charge and shape of the substrate, so that the substrate cannot bind to the active site, or cannot be catalyzed to form a product. In a narrow range of pH, the structural and morphological changes of enzymes and substrates may be reversible. However, if the level of pH changes significantly, the enzyme and substrate may be denatured. In this case, the enzyme and the substrate do not recognize each other, so there will be no reaction. Optimal pH All enzymes have an ideal pH value, which is called optimal pH. Under the optimum pH conditions, each enzyme showed the maximum activity. For example, the optimum pH of an enzyme that works in the acidic environment of the human stomach is lower than that of an enzyme that works in a neutral environment of human blood. When the pH value deviates from the ideal conditions, the activity of the enzyme slows down and then stops. The enzyme has an active site at the substrate binding site, and the shape of the active site will change with the change of pH value. Depending on the extreme extent of the enzyme and pH changes, these changes may permanently "destroy" the enzyme, or once the conditions return to the desired range of the enzyme, the enzyme will return to normal. Related Services Enzyme Kinetics To discuss more service details, please contact us.
The effect of substrate concentration on the rate of enzyme-controlled reactions Remember that in biology or biochemistry, the reactant in an enzyme reaction is known as the "substrate". What follows is a very brief and simple look at a very complicated topic. Anything beyond this is the stuff of biochemistry degree courses! A reminder about the effect of concentration on rate in ordinary chemical reactions If you have done any work on rates of reaction (especially if you have done orders of reaction), you will have come across cases where the rate of reaction is proportional to the concentration of a reactant, or perhaps to the square of its concentration. You would discover this by changing the concentration of one of the reactants, keeping everything else constant, and measuring the initial rate of the reaction. If you measure the rate after the reaction has been going for a while, the concentration of the reactant(s) will have changed and that just complicates things. That's why initial rates are so useful - you know exactly how much you have of everything. If you plotted a graph of initial reaction rate against the concentration of a reactant, then there are various possibilities depending on the relationship between the concentration and the rate. If the rate is independent of the concentration This is called a zero order reaction. If the rate is proportional to the concentration This is called a first order reaction. If the rate is proportional to some power of the concentration greater than one In this case, you get a curve. If the rate was proportional to the square of the concentration, that's a second order reaction. With reactions controlled by enzymes, you get a completely different type of graph. Plotting initial rates of enzyme-controlled reactions against substrate concentration The graph for enzyme controlled reactions looks like this: Two minor things to notice before we discuss it . . .
So why is the graph the shape it is? For very, very low substrate concentrations, the graph is almost a straight line - like the second chemistry rate graph above. In other words, at very, very low concentrations, the rate is proportional to the substrate concentration. But as concentration increases, increasing the concentration more has less and less effect - and eventually the rate reaches a maximum. Increasing the concentration any more makes no difference to the rate of the reaction. If you know about orders of reaction, the reaction has now become zero order with respect to the substrate. The reason for this is actually fairly obvious if you think about it. After a certain concentration of substrate is reached, every enzyme molecule present in the mixture is working as fast as it can. If you increase the substrate concentration any more, there aren't any enzyme molecules free to help the extra substrate molecules to react. Is this unique to enzyme-controlled reactions? No! It can happen in some ordinary chemistry cases as well, usually involving a solid catalyst working with gases. At very high gas pressures (in other words, very high concentrations of gas molecules), the surface of the catalyst can be completely full of gas molecules. If you increase the amount of gas any more, there isn't any available surface for it to stick to and react. Vmax and KM The maximum rate for a particular enzyme reaction is known as Vmax. (That's V for velocity - a bit confusing for chemists where V is almost always used for volume!) This is easily measured by drawing a line on the graph: This is sometimes reported as a "turnover number", measured as the number of molecules of substrate processed by a single enzyme molecule per second, or per minute. KM is known as the Michaelis constant or the Michaelis-Menten constant (for reasons which needn't concern us), and is a useful measure of the efficiency of an enzyme. KM is the concentration of the substrate in mol dm-3 which produces a reaction rate of half Vmax. So it is found like this . . . A low value of KM means that the reaction is going quickly even at low substrate concentrations. A higher value means the enzyme isn't as effective. |
What would happen if the structure of an enzyme changed and under what circumstances might this happen?
Pos Terkait
Copyright © 2024 membukakan Inc.
