Enzymes Overview

Unlock the power of enzymes! Learn how these biological catalysts work and what affects their function.

What are Enzymes? A catalystis a substance that speeds up a chemical reaction.Enzymesare biological molecules (typically proteins) act as a catalyst for chemical reactions that take place within cells. They are vital for life and serve a wide range of important functions in the body, such as aiding in digestion and metabolism.Some enzymes help break large molecules into smaller pieces that are more easily absorbed by the body. Other enzymes help bind two molecules together to produce a new molecule. Enzymes are highly selective catalysts, meaning that each enzyme only speeds up a specific reaction.The specific action of an enzyme with a single substrate can be explained using aLock and Keyanalogy first postulated in 1894 by Emil Fischer. In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sizedkey (substrate) fitsinto thekeyhole (active site)of thelock (enzyme).Smaller keys, larger keys, or incorrectly positioned teeth on keys (incorrectly shaped or sized substrate molecules) do not fit into the lock (enzyme). Only the correctly shaped key opens a particular lock. This is illustrated in the graphic below: Label the parts! Enzyme, Substrate, Active site, Product Substrate Enzyme Active Site Product Product How does an enzyme-substrate-complex resemble a lock and key? How Enzymes Affect Activation Energy Remember that enzymes are catalysts. Activation energyis the energy needed to activate a chemical reaction.Enzymes speed up reactions by lowering the activation energy of a reaction. They do this by binding to a substrate and holding it in a way that allows the reaction to happen more easily.In the chart above, the blue line represents the reaction WITHOUT enzymes and the green line represents the reaction WITH enzymes. As you can see the reaction WITH the enzymes requires much less energy. Activation Energy The red line represented the chemical reaction without the enzyme, and the black line represents the activation energy with the enzyme. In what way does the addition of the enzyme effect the chemical reaction? Optimal Conditions Enzyme activity can be affected by a variety of factors, such as temperature, pH, and concentration. Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions can cause an enzyme to denature, or lose its ability to bind to a substrate.Temperature (Chart a): Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. However, extremely high temperatures can cause an enzyme to lose its shape (denature) and stop working. The optimal temperature is the highest temperature that makes enzymes better before they start getting bad, so the TOP of the curve. The optimal temperature in the chart below is 35 degrees.pH (Chart b): Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity. Extreme pH values can cause enzymes to denature. As with temperature, the optimal pH range is when the enzyme is performing at its best. The optimal pH in the chart below is a pH of 7.Concentration (Chart c): Concentrationis just how much of something you have in one place. Increasing enzyme or substrate concentration will speed up the reaction, as long as there is not to many. If the concentration gets too high, it will not hurt the enzyme, it just will not become any more productive. As the chart shows below, the production just balances, it does not go back down. Enzyme Practice 1 An experiment was performed to test the effect of temperature and pH on the activity ofEnzyme X. The following data was collected during the experiment:Use the data to answer the following questions: 1) What is the optimum pH of enzyme X? 7 8 9 10 2) What is the optimum temperature of enzyme X? 10 20 30 40 3) Enzyme X performs critical life functions. Use the data above to explain why a fever of 40 degrees may be dangerous: It will make the enzyme move too fast, which will burn the person. It will cause the enzyme to denature, which means it will get bigger. It will cause the enzyme to denature, which means it will stop working. I will turn the enzyme into DNA, which will make it stop working. Using the 2 graphs above, at what pH do the following enzymes work best?Sucrase: 4Lipase: 8Pepsin: 3Trypsin: 8 Vocabulary Enzyme A protein that is a catalyst for chemical reactions. Catalyst A substance that speeds up a chemical reaction Denature When the active site of an enzyme changes so that the substrate no longer fits. Substrate the substance on which an enzyme acts. Active Site the specific region of an enzyme where a substrate binds Product the substance that enzymes turn substrates into