Biology Coursework on Enzymes.

Authors Avatar
Biology Coursework on Enzymes

Name: Brijel Limbachia

Form: 12.92

Teachers: Mr Lotsu and Mrs Stewart

Enzymes in General

I will first of all talk about enzymes in general. This means that I will talk about what enzymes are, how being in certain conditions affects the enzyme itself. I will also talk about how substances can increase the % transmission between the enzyme and the substrate.

What are enzymes?

The catalysis that takes place in organisms is defined as the acceleration of a chemical reaction by some substance which itself undergoes no permanent chemical change. These kinds of catalysts, which are in biochemical reactions, are called enzymes. Enzymes are responsible for almost all of the chemical reactions in living organisms. Without enzymes, these reactions take place at a rate that is far too slow for the pace of metabolism.

An active enzyme could make a certain reaction speed up, but not all living things need all the reactions to be quick all the time. It's more accurate to say that enzymes react with simpler molecules to produce a stable reaction system in which the products of any reaction are made when they are needed, also in the amount that they are needed.

All known enzymes are proteins. Enzymes are high molecular weight compounds made up of chains of amino acids that are linked together by peptide bonds. As you know that enzymes are composed of proteins, these proteins are globular proteins. These globular proteins have a complex tertiary and sometimes quaternary structure, where polypeptides are folded around each other to form a roughly spherical, or globular shape.

Here is a diagram to show the three-dimensional shape of an enzyme:

The green molecules are the substrate in the enzyme (on the left), and the enzyme itself is on the right.

Here is a diagram to show the three-dimensional structure of an enzyme molecule:

The shape of an enzyme molecule is very important, if the molecule is altered in any way, the enzyme can't combine to its substrate, therefore the enzyme will not be able to function any more. The hydrogen bonds and the ionic forces maintain the enzyme itself, and so their function can be affected by the changes in temperature and also changes in pH can affect their function.

Enzymes have several properties; I shall explain them in full below:

Enzymes are specific, this means that each enzyme usually catalyses only one reaction.

Enzymes combine themselves with their substrates so they can form temporary enzyme-substrate complexes.

Enzymes are not changed or used up by the reaction they catalyse; this therefore means that they can be used again and again.

Enzymes work very quickly and each enzyme has its own turnover numbers.

Enzymes are very sensitive to changes in temperature and pH.

Many enzymes need other chemicals called cofactors, in order to function.

The enzyme function can be slowed down or even stopped by inhibitors.

As you know that enzymes are compounds that are made up of chains of amino acids that are linked together by peptide bonds, here is a diagram to show this:

The Specificity of enzymes

Talking about digestive enzymes, these enzymes catalyse only one reaction. Trypsin, for example, can begin the digestion of a wide variety of foods, which are rich in proteins (eggs, pork, chicken, and Soya). But when you look at how the enzyme Trypsin works at the molecular level, you can see that this enzyme is specific. Trypsin cuts an amino acid chain at a point between a lysine and an arginine residue, and nowhere else. Most proteins have these two amino acids next to each other at some points in their polypeptide chain, and so can be partly digested by Trypsin.

My coursework, which is on enzymes, will investigate the variable of pH. Therefore my aim will be:

Aim: I am investing the effect of pH on the activity of the enzyme Trypsin; this is when this enzyme reacts with the substrate Caesin. I am also investing which pH's make the enzyme Trypsin denature.

Preliminary Work

My preliminary plan was:

Preliminary Hypothesis

I predict that as the enzyme Trypsin is in pH 8 (this is the optimum pH for the enzyme Trypsin) the enzyme will be fully active and therefore the % transmission will be high. But further away from pH 8, (more alkaline or more acidic) it will be less active; this therefore means that the % transmission will decrease.

I am expecting that the enzyme Trypsin react the fastest in pH8, this is because from background research it is said that pH8 is the optimum pH for the enzyme Trypsin.

I will explain more about the enzyme Trypsin and its optimum pH in the actual predication/hypothesis.

This is the first materials list and method I came up with before I started the actual preliminary experiment:

Preliminary Materials

Caesin suspension, 0.5% (using skimmed milk powder)

Trypsin solution, 0.5%

Distilled Water

Test tubes and test tube rack

Graduated pipettes or syringes

Glass beakers

Thermometer

Colorimeter

Stopwatch

Preliminary Method

) Set up a water bath using a beaker at room temp.

2) Put 5cm3 of casein suspension in one test tube and 5cm3 of Trypsin in another.

3) Put both of the test tubes in the water bath (beaker of water at room temperature); leave the test tubes in there until it reaches room temperature.

4) Now make a control test tube with 5cm3 of distilled water with the same amount of casein suspension.

5) Now take out and mix together and immediately add the 5cm3 of pH buffer solution, once added the entire solutions shake, and also the stopwatch should be immediately started as soon as all the solutions were added.

6) Observe the contents of the test tube and record your results, place the contents in a colorimeter every 30 seconds. And record the results obtained, in a suitable table, and plot a graph.

7) Repeat this experiment but using a range of pH's. The range starts from 5 and ends at 10. But you have to make sure that the volume, temperature etc. is kept the same in order for it to be a fair test.
Join now!


Problems that were encountered in the Preliminary experiment:

After carrying out my first preliminary experiment I encountered several problems. Here are the problems that I encountered and the solution of the problem:

The very first problem that I encountered was that my experiment never worked, the reaction never took place. The problem that I found out that I was using the wrong concentrations, I should not have been using 0.5% casein suspension, I found that I should have been using 4% of casein suspension. This was the reason why the experiment never took place.

...

This is a preview of the whole essay