The Effect of Certain Conditions on the Efficiency of Enzymes - Biology Essay Example

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To investigate the best conditions for the breakdown of H202 (Hydrogen Peroxide) by enzymes.


If the enzymes in liver and potato break down H202 in various conditions of pH, temperature, and surface area, then the fastest reaction will be with neutral pH, warm temperature, and ground up (surface area).

Procedure Guidelines

In this lab, all the reactions are done in a 24-spot spot plate. Each spot is filled about halfway with H202, and then the substrate is added. The temperature and pH were then measured as needed. To see the outcomes of all the reactions, look at the attached data chart.

For results see attached diagrams and graphs.


An enzyme is an organic substance that increases the speed of a reaction. In this lab the enzymes have 3 conditions: pH, temperature, and surface area. Both the liver and the potato contain catalase. A substrate is the substance that the enzyme is reacting upon. The substrate fits into the enzyme’s active site, where it is helped along. If an enzyme denatures, it loses its shape, which means that the substrate will not fit anymore, so the enzyme becomes useless. The substrate of the enzyme being tested is H202. Here is the reaction: H202 –>H20 + O2. This certain enzyme, catalase, would not work on any other chemical because its active site is specifically shaped for H202. Any other chemical would not fit into the active site. Catalysts are a more general category than enzymes. Catalysts are substances that reduce the activation energy of a reaction. Enzymes are catalysts made out of proteins. Not all catalysts are organic, but all enzymes are.

MnO2 was a catalyst because it speeded up the reaction. Sand was not a catalyst because it did nothing. Neither are enzymes because they are not organic. Sand shows how the reaction would go all by itself. Anything faster than that would show some improvement from the conditions.

The chunk of liver and potato were the basic reactions in this lab. They are the control for many of the other conditions. The chunk of liver did quite well with a score of 3. The chunk of potato however only got 1.5.

In the ground vs. chunk reactions, the ground potato did very well compared with the chunk of potato. However, the ground liver did not do as well as the chunk of liver. This was probably because there was more liver in the chunk of liver reaction than in the ground liver. The ground enzyme substance did better because more of the enzyme could meet the substrate at one time.

In the temperature reactions, the warm liver did the best, followed by room temp, cold, and then boiled. While each enzyme has a preferred working temperature, warm usually is a good one for most. Room temperature and cold ranked based on how close they were to warm. The boiled one did not do well at all. In fact it did nothing. This is because after about 98?, the enzymes in a substance denature, the lose their shape, therefore rendering them useless. The boiled liver had already reached this point, and therefore had no potent enzymes left to speed up the reaction.

In the pH reactions, the pH of 12 did the best with 2, followed by pH 1 and 6 with scores of 1.5. All of the reactions in this group did worse than the control that had nothing added. All enzymes have their own favorite pH to work at, and according to records, the optimum pH for catalase is around 7. However, these reactions did not show that because the pH of 6 would have done the best. The reason for this is probably that the pH that the reaction is already good enough that adding more substances takes away from the concentration of the substrate, hampering efficiency.

In the reusability reactions, the reused liver scored almost as well as the basic chunk of liver, but the reused H202 did not work so well. This is because while catalysts (the liver in this reaction) can be used over and over again because they are not affected by the reaction, the substrate cannot, because it has already been reacted. In reality, the H202 was less H202 and more just water (the oxygen having dissipated). Liver and water do nothing, so no bubbles were seen.

Peroxisomes are organelles found in the liver and kidneys that break down things that are bad for your body like alcohol and Hydrogen Peroxide. Catalase is one of the enzymes inside peroxisomes that does the breaking down of H202. H202 only bubbles when poured on the blood instead of on the skin because blood contains peroxisomes carrying catalase, which react with the H202.


In the chunk reactions, the liver did well but the potato did not. However, in the ground up reactions, the ground liver was about the same as the chunk liver, while the ground potato was way better than the chunk potato. In the temperature reactions, warm did the best, followed by room temp., then cold. The boiled liver made no difference to the the reaction at all. In the pH reactions, all three did pretty badly with the best one (ph of 12) only scoring a 2. In the reusability reactions, the reused liver worked as well as the chunk liver, but the reused H202 did not work at all.

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