Chemistry Investigation Essay Research Paper Investigate A

Chemistry Investigation Essay, Research Paper

Investigate A Factor Which Affects the Rate Of Fermentation Of Yeast

This experiment is investigating one of the factors which affects the rate of fermentation of yeast.

Several factors affect the rate of reaction:

Ø Increasing the concentration. (See the lock and key theory.) If the substrate (glucose) is increased, then there would be more keys for the locks, therefore an increase in reactant concentration leads to an increase in reaction rate.

Ø The surface area, the bigger the surface area, the faster the reaction time is, as the reactant can reach more parts.

Ø The temperature, an increase in temperature leads to an increase in reactant rate. Generally, as the temperature is increased, the particles get more energy, so they bump into one another more, therefore speeding up the reaction time. This is called the collision theory, which I will discuss in greater depth later.

Ø Whether or not there is a catalyst. A catalyst speeds up the rate of reaction and remains chemically unchanged by the end of the experiment. A catalyst lowers the activation energy. This is the energy needed to start a reaction.

The variable that I have decided to change is the temperature. I have decided to alter the temperature of the yeast and time the amount of carbon dioxide that will be given off at different temperatures. I have decided to time how much carbon dioxide is given off in five minutes.

Throughout the investigation, I will keep the temperature the same as I have specified for each reading. For example, if I am taking a reading in which the temperature must be 5 degrees, I will make sure that the yeast is kept at this temperature. When I am altering the temperature of the yeast, I will place it in a water bath of the specified temperature, which makes the temperature much more accurate. For example, if I heat up the yeast using a Bunsen burner, I could heat it up too much, thereby denaturing the enzymes and ruining the experiment. After the enzymes have been denatured, they can no longer react.

It will also be important not to agitate the solution at all, because this would cause collisions between particles, speeding up the reaction time and making the test unfair.

While doing an experiment such as this, it is vital to be safe at all times. You should stand up at all times, making sure that stools are firmly under desks. When the Bunsen burner is not being used, make sure that the orange safety flame is on. Use a heatproof mat and safety gauze.

When I change the chosen variable (temperature), I predict that the reaction rate will increase. However, after the temperature has reached about degrees, the enzymes will be denatured, therefore the reaction rate will decrease, eventually reaching zero. Enzymes function most efficiently within a physiological temperature range. Since enzymes are protein molecules, high temperatures can destroy them. An example of such destruction, called protein denaturation, is the curdling of milk when it is boiled. Increasing temperature has two effects on an enzyme. First, the velocity of the reaction increases somewhat, because the rate of chemical reactions tends to increase with temperature; second, the enzyme is increasingly denatured. Increasing temperature thus increases the metabolic rate only within a limited range. If the temperature becomes too high, enzyme denaturation destroys life. Low temperatures also change the shapes of enzymes. With enzymes that are cold sensitive, the change causes loss of activity. Both excessive cold and heat are therefore damaging to enzymes.

The degree of acidity or basicity of a solution, which is expressed as pH, also affects enzymes. As the acidity of a solution changes, e.g. the pH is altered–a point of optimum acidity occurs, at which the enzyme acts most efficiently. Although this pH optimum varies with temperature and is influenced by other constituents of the solution containing the enzyme, it is a characteristic property of enzymes. Because enzymes are sensitive to changes in acidity, most living systems are highly buffered; e.g. they have mechanisms that enable them to maintain a constant acidity. This acidity level, or pH, is about 7 in most organisms. Some bacteria function under moderately acidic or basic conditions; and the digestive enzyme pepsin acts in the acid milieu of the stomach. There is no known organism that can survive in either a very acidic or a very basic environment.

Most chemical reaction happen faster when the temperature is high. At higher temperatures molecules move around faster, this makes it easier for them to react together. Usually, a rise of 10 degrees Celsius will double the rate of a chemical reactor. Most of the chemical reactions happening inside a living organism are controlled or catalysed by enzymes.

My prediction is also backed up by the lock and key theory . Enzymes are proteins that are BIOLOGICAL CATALYSTS. A catalyst is something that changes the rate of a chemical reaction without itself undergoing any change.

Enzymes have an active site. This is a special shape, in which a specific molecule can fit, e.g. starch fits into the active site of amylase. This is called the lock and key theory. A lock is a special shape and only a key of the required shape can