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Biology Open-Ended Investigation Essay Sample

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Biology Open-Ended Investigation Essay Sample

Introduction: Enzymes are catalysts, because they control the rate of the reaction that helps chemical reactions work properly within living organisms. They are specialised proteins that have a unique shape and chemical composition that creates an active site for connection between the enzyme and substrates. The substrate molecules bind to the active site, inducing a temporary change in the shape of the enzyme known as induced fit. Enzymes catalyse and modify the rate of biomechanical reactions without becoming a part of the product of reaction. Like all proteins, enzymes are made in the ribosomes by linking together amino acids from the cytoplasm. Their action is dependent upon their ability to fit with the molecule reactants; otherwise the reaction will not proceed. For example, study from previous experiments demonstrates that the maltose present will not turn into glucose until it enters the intestine (different catalyst). There are diverse types of enzymes that work best under certain optimum conditions including temperature, pH and substrate concentration. Enzymes can be used more than once and are very important to cell functioning; therefore only small quantities of them are required in the cell.

The effect of temperature on enzyme activity is; lower temperatures (0 C) will cause the substrates to move at a significantly slow speed to collide and react with the enzyme therefore very little product will be produced, where as too high of a temperature (100 C) will cause denaturing in the enzyme and very little product will be produced, and lastly room temperature (37 C) will provide the most product of the temperatures being tested. In the presence of starch iodine turns blue/black in the temperatures of 0 C and 100 C (sometimes present in 37 C temperatures) and if no starch is present it is a pale yellowy-brown colour. Iodine can therefore be used to monitor the breakdown of starch into sugar. When the iodine no longer changes colour, you know all of the starch has been broken down. Lastly in the presence of maltose, the benedicts solution turns blue at 0 C and 100 C temperatures. Where as the salivary amylase catalyzes the breakdown of starch to maltose and it turns red.

Formula: Starch Disaccharide Monosaccharide


Enzyme activity occurs in a specific temperature range (37 C) in order to help chemical reactions work properly in living organisms. Aim: To test the effect of temperature on the ability of salivary amylase to catalyse the breakdown of starch to maltose.

• Clean test tubes 6x (3x for Benedict’s and 3x for Iodine)
• Test tube rake 1x
• Glass rod
• 250mL Beaker 3x (big enough to act as water baths for test tubes)
• Bunsen burner 2x
• Tripod 2x
• Gauze mat 2x
• Thermometers 3x

• Test tube holder 1x
• Ice cubes
• Starch solution
• Benedict’s exp
• Matches
• Kettle for boiling hot water
• Test tube pegs 6x
• Pipet 1x

Step 1: Set-up equipment as drawn below
Step 2: Place all 6 test tubes in the test tube rack holder and number them from 1-6
Step 3: Dribble 1cm of saliva into each of the four test tubes
Step 5: Perform the following the test tubes:-
1. Test tube 1-37 C
• Put test tube 1 (benedict’s) and 4 (iodine) into a beaker of water at 37 C and keep at that temperature in a water bath Add about 10 drops of starch solution • Keep at 37 C for 15 minutes

• Test the contents of the test tube for sugar, with iodine • Record the colour change and sugar concentration
2. Test tube 2-100 C
• Heat test tube 3 (benedict’s) and 5 (iodine) until the saliva boils • Add about 10 drops of starch solution
• Stand in beaker of boiling water for 15 minutes • Remove, test for sugar, record results

3. Test tube 3-0 C
• Put test tube 3 (benedict’s) and 6 (iodine) in a beaker of full of ice cubes • Leave it until the saliva is at 0 C
• Add about 10 drops of starch solution
• Leave on ice for 15 minutes
• Remove, test for sugar, record results
Step 6: Repeat experiment several times to ensure the results are reliable and accurate, if you are unable to repeat the experiment get the data from another student in my class testing for temperature.

Scientific Diagram of Set-Up
Variables: Temperature (0 C, 37 C, 100 C)
Control: Same temperature, saliva, size tubes, 10 drops of starch solution, time (15 minutes)


0 C 37 C 100 C Iodine 1 Iodine 2 Previous experiment Average Benedict’s 1 Benedict’s 2 Previous experiment Average

Effect of temperature on enzyme activity

Red – Previous experiment
Blue – Sham’s experiment
Green – Ulia’s experiment

When the saliva and starch were in 0 C and 100 C temperature water, there was starch present that means the enzymes were not active. However, water at temperature 37 C the salivary amylase catalyses the breakdown of starch to maltose. This was proven in the benedict’s and iodine experiment tests. During the benedict’s experiment the saliva at 37 C turned red and throughout the iodine test the saliva at 37 C was clear. This establishes the enzymes are active at 37 C for both the iodine and benedict’s tests. The results of the effect of temperature on enzyme activity were as expected and supported my hypothesis. There may have been some faults within my experiment, as it is likely in majority of the experiments completed, such as human error in terms of the amount of iodine drops placed in each test tube and contamination.

The results recorded during the experiment were similar to the results recorded during a previous experiment done in class a couple of weeks ago. This indicates the results are highly likely to be accurate and reliable, however additionally repeating the experiment and collecting data off other students in my class doing temperature will ensure results are precise and consistent. This is a significant factor that needs to be addressed in order to improve the investigation being undertaken. There are other ways that could possibly overcome problems during an experiment to improve the investigation in the future is ensuring the measurements such as the amount of saliva in each test tube, the number of drops of iodine placed in the test tubes is accurate, the temperature ranges are accurate and constantly kept on the same temperature and time limit of test tubes placed in the beaker is exactly on time; also known as the controls of the experiment.

Saliva acts within exceedingly narrow perimeters of salivary amylase. Enzyme activity is optimum at 37 C, where as both 0 C and 100 C will cause denaturing in the enzyme.

Identified Risk Eliminating the Risk Females with long hair Tie hair back and tuck in the back of shirt Acid present Wear safety goggles provided by the teacher to protect eyes from burning which can lead to permanent damage such as blindness Burn part of your body with  the Bunsen burner Do not place hand anywhere near the flame and when not in use keep as far away from flammable materials as well as turning it from a blue flame to the orange flame Heated glass beaker may shatter Keep an eye on the Bunsen burner heating the beaker and if need to remove beaker from the Bunsen burner then do but carefully without burning yourself – Wear enclosed shoes – Wear safety glasses to stop the glass getting to the students eyes and damaging them Student cuts themselves while cutting materials If not sure on how to cut, ask teacher to assist you while cutting and make sure student doesn’t fool around and cuts the material slowly Iodine solution is present (stain skin, and surfaces)

– Where a lab coat provided by the teacher – Wear long clothing to reduce the risk of getting it on your skin – Wear enclosed shoes Transmission of aids due to an individuals spit Ensure all test tubes are absolutely clean before putting it away and do not pass on the spit or touch it without wearing gloves Gas leak/on with flames around – fire Ensure the gas is off before turning the gas knob on as well as making sure there is a fire distinguisher in the classroom Tip the boiling hot water on yourself or others Make certain that all students are away from the person holding the boiled water and when pouring boiling water in the beaker make sure it is placed on a flat surface to minimise the chance of it tipping. This also includes instead of holding it with a chance of dropping the beaker place it on the bench. Also wear enclosed shoes A student slips from melted ice on the floor Make sure there is no ice on the floor and if there is pick it up straight away and wipe the water on the floor.

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