Have you ever wondered how antibiotics and other medicines are able to stop dangerous infections? How do such medications kill microorganisms without in general harming the person the microorganisms are infecting? Because many different types of microorganisms can infect us, we have had to develop an amazing number of ways to deal with these harmful microbes. Fungal infections can be particularly dangerous, but we have developed many different antifungal medications that can usually deal with these infections. But how do antifungal medications work, and how effective are they? In this science project, we will test how well different common antifungal medications can stop the growth of baker's yeast, a harmless variety of fungus often used in baking.
Problem/ Objective : Determine how different antifungal medications slow or stop the growth of fungus.
Left untreated, fungal infections can lead to serious medical conditions. Consequently, it is important to know what kind of antifungal medicine, and how much, to take to kill a certain type of fungus. Some of the most common fungal infections are athlete's foot, nail infections, and yeast infections. The fungus group includes molds, yeast, mushrooms, and more. Fungi actually make up a kingdom of organisms separate from plants, animals, and bacteria. Different antifungal agents work in different ways to kill fungus. Two of the most common antifungal agents used in nonprescription antifungal medicines areazoles and allylamines. Azole and allylamine both work by disrupting the fungus' ability to make ergosterol, which is a chemical compound important for the fungus to make a strong cell membrane. Without a strong cell membrane, the fungal cells could become leaky and die. Ergosterol is not in plant or animal cells, which makes it a good compound to target if you only want to kill the fungus without hurting infected plants or animals (including people). Azoles and allylamines disrupt the fungus' ability to make ergosterol in different ways, as shown in the molecular pathway diagram in Figure 1 below. A molecular pathway is a series of chemical reactions that take place within a cell. In this diagram, arrows pointing down indicate a chemical reaction. This means that squalene is normally converted to lanosterol during a chemical reaction aided by the enzyme squalene epoxidase. An enzyme is something that helps a chemical reaction take place. The lanosterol is then converted to ergosterol with the help of the enzyme lanosterol 14α-demethylase. Ergosterol is used by the fungal cells to create a functional cell membrane. The sideways "T"s in the diagram show how a chemical reaction can be stopped. Allylamines stop the function of the squalene epoxidase enzyme, thus blocking the fungus from making lanosterol. Azoles stop the function of the enzyme lanosterol 14α-demethylase, thus blocking the fungus from making ergosterol.A common nonprescription azole found in antifungal medications is called clotrimazole, while a common nonprescription allylamine is called terbinafine. Tolnaftate (also sold as Tinactin) is another common nonprescription antifungal agent, and it is thought to inhibit squalene epoxidase, like the allylamines. Nonprescription medicines, also called "over-the-counter" medicines, do not require a doctor's prescription to buy, so that anyone can go into a pharmacy and buy them, while a doctor's prescription is needed to buy prescription medicines. Undecylenic acid, another common nonprescription antifungal agent, can be used to fight fungal infections as well as infections caused by other microorganisms. Undecylenic acid is derived from the castor bean, which contains toxic compounds. Scientists do not completely understand how undecylenic acid fights fungal infections, but they think that it interferes with the fungus' lifecycle. Specifically, it may stop the fungus from reproducing (making more fungus). Different types of fungus react to...
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