Stage 2: Human BiologySummative Practical: Pepsin
Background Information:
What are enzymes and how they work?Enzymes are necessary proteins that are crucial in the maintenance and activity of life. CITATION Amaed l 1033 (Inc, Undated). Enzymes increase the rate of a chemical reaction without itself undergoing any permanent chemical change. All chemical reactions that occur within a living organism rely on the catalytic actions of enzymes, which is why enzymes are called Biotransformation. Currently there is an estimate of 4,000 kinds of enzymes of whose actions are well known CITATION Amaed l 1033 (Inc, Undated). Enzymes work best in environments similar to the environments of living organism, and they synthesize and degrade materials that add up to the building blocks of the organism and create energy for supporting life CITATION Amaed l 1033 (Inc, Undated). The enzymes function as a highly selective catalysis in a way which they selectivity catalyse specific reactions only and specific materials such as substrates CITATION Amaed l 1033 (Inc, Undated).
What is the function of pepsin? Where is it found? Pepsin is a type of enzyme, which can be found in the gastric juice within the stomach. Pepsin\'s job is to break down proteins such as meat, eggs, seeds or dairy products, into smaller peptide chains CITATION The15 l 1033 (Britannica, 2015).
What factors that affect the activity of pepsin?A factor that can affect the activity of pepsin used for this practical are the temperature. At the temperature zone of <10o and 23o, the active site shrinks and changes shape, this takes the chemical reaction a longer time to occur. At the temperature of 37o the cause of collision between the substrate and the enzyme increases due to the rise increase of temperature, this causes the chemical reaction to take place at a much faster pace. At the temperature of 70o the active site of the enzyme is destroyed as the enzyme denatures due to the high amount of heat. (Pham, 2016)What is Hydrochloric Acid? Why is the egg white solution used in this practical?Hydrochloric Acid (HCL) is a very strong, clear solution of Hydrogen chloride and water. This acid is a highly eroding chemical compound with several ways of use in industries. It is also found in diluted amounts in the stomach of humans and animals as gastric acid CITATION wised l 1033 (wiseGEEK, Undated). Hydrochloric acid was used within this practical to act as a substitute which was close to the gastric acids, to help with the breakdown of the egg whites proteins. The egg white proteins are used within this practical as a substitute for proteins, in which the Pepsin and hydrochloric acids can act upon, by breaking the egg white proteins into smaller egg white proteins peptide chains.What is the lock and key model Theory and the Induced Fit model Theory?The lock and key model was formulated by Emil Fisher, as well as the induced fit model created by Daniel E. Koshland, are both enzyme model hypothesis. Emil Fisher\'s Lock and Key Theory was created in 1894. It is stated that the enzyme is a ‘lock\' into which substrates fits like a ‘key\'. The shape of the active site and the substrate molecules are complementary. It is said that the shapes are complementary, so that the enzyme molecule holds the substrate , molecule close together, forming the unusable intermediate compound, the enzyme substrate complex, it dissociates to form enzyme products CITATION Majed l 1033 (Differences, Undated). The Induced Fit Theory was formulated by Daniel E. Koshland, in 1959. According to his hypothesis the active site does not have a rigid ‘lock and key\' conformation. The binding of the substrate molecule to the enzyme molecule induces to modify the shape of the active site so that it becomes complementary to the substrate molecule. This is called the induced fit. This hypothesis is possible because of the flexibility of the protein molecules CITATION Majed l 1033 (Differences, Undated).
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(Enzyme working mechanism, 2013.) (Induced Fit Model Theory)



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(Difference between Lock and Key hypothesis and Induced Fit hypothesis, Undated) (Lock and Key Model Theory)



Aim: To find out what temperature Pepsin reacts best to and at what temperature Pepsin denatures at.
Identify variables: Independent variable: Temperature (<10o, 23o, 37o, 70o) Controlled variable: The volume of the chemicals used. (Hydrochloric acid, Pepsin,