Living cells undergo a process called transpiration, and produce byproducts that are harmful to the cell. One of the byproducts of cell metabolism is hydrogen peroxide. Excess hydrogen peroxide is toxic to living cell. Therefore, it must be disintegrated into less toxic substances so that it does not damage the cells. Since hydrogen peroxide is produced at a very high rate in the cells, it necessitates a catalyst, which speeds up the rate of its conversion so that it does not accumulate in the cell. A catalyst reduces the energy needed to activate a chemical reaction. This way, the rate of the reaction is speeded up.
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Question: what is the role of enzymes in living cells? The hypothesized for this experiment is; does enzyme activity take place in living cells?
- Plastic beakers
- Fresh hydrogen peroxide solution
- Freshly cut liver
- A pen
- A ruler with centimeter markings
- Dilute hydrochloric acidic (Hcl)
- Dilute sulfuric acid (H2SO4)
- Using a pen, clearly inscribe on the stickers, the names or the chemical formulas of the three liquids provided.
- Attach the stickers to the plastic beakers provided.
- Carefully fill the plastic beakers with the respective liquids provided to about 1/3 of the beaker.
- Using the ruler, measure a one-centimeter cube of the fresh liver, and cut out the piece using a scalpel or the cutting tool provided. Cut out two other pieces of similar dimensions or pieces equivalent to the number of the liquids provided.
- Using forceps add one liver cube to each plastic beaker with the liquids (H2SO4, Hcl and H2O2), and then observe in which beaker bubbles are produced.
- Repeat step five using a small amount of yeast.
Bubbling or foaming was observed in the beaker that contained hydrogen peroxide, for both the fresh piece of liver and yeast. An odorless gas was produced. No bubbles were formed in the beaker that contained Hcl and H2SO4.
Enzymes speed up the rates of reaction in living cells. Enzymes that speed up reactions in living cell are called catalysts. Without these enzymes, reactions inside the cells would occur at a very slow rate. Living cells contain an enzyme known as Catalase. Enzymes in living organisms are specific. That is, they speed up only a single reaction. Therefore, there are several thousands of special enzymes within a cell speeding up numerous different disconnected or linked chemical reactions. The materials, which are transformed or acted upon by these enzymes, are known as substrates and the resultant materials are the end products (Roberts & Ingram, 2001).
When yeast and the freshly cut piece of liver were placed inside a beaker with hydrogen peroxide, bubbles were formed, due to the breakdown of hydrogen peroxide by Catalase. The end products of this reaction were oxygen and water. The chemical equation (2H2O2—–> 2H2O + 2O2), represent the reaction that took place (Nuffield Foundation, 2011). The process of bubbling signifies production of oxygen gas. Catalase speeds up the conversion of hydrogen peroxide to water and oxygen, at an extremely high rate of up to two hundred thousand reactions in every second. H2SO4 and Hcl do not disintegrate in the presence of Catalase; hence, no bubbling when yeast and a piece of liver were added.
The experiment done using yeast and a piece of fresh meat confirmed that enzyme activity takes place in living cells. The oxygen that was produced through bubbling when yeast and a piece of liver were added to hydrogen peroxide support the hypothesis of the study.
Nuffield Foundation. (2011). Investigating an enzyme-controlled reaction: catalase and hydrogen peroxide concentration. Web.
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Roberts, M., & Ingram, N. (2001). Biology. Cheltenham: Nelson Thornes.