Oxygen + Glucose ➔ Carbon + Water
Dioxide
602 + C6H12O6 ➔ 6CO2 + 6H2O
If the temperature is too cold, the enzyme shape is altered slightly and the reaction does not happen, as the substrate no longer fits in. This does not have a long-term effect on it as if the enzyme is warmed up; it will return to its original shape.
If it's too hot (say above about 38°C), the enzyme shape is again altered and so the reactions once more do not happen. This is bad news though as the higher temperatures actually permanently destroy the enzyme. If boiled, for example, the enzyme would never go back to its original shape. It would never work again.
The best temperature or "optimum" temperature is when the enzyme's shape is the best to fit the substrate molecule. For warm-blooded mammals like humans, this is our body temperature (37°C).
This is the shape of graph I am expecting:
The red represents the steady increase in enzyme activity as the temperature rises.
The blue represents the start of the denaturing of the enzymes
The green represents the total denaturing of the enzymes and the stopping of the wriggling.
The X represents the optimum temperature.
Preliminary
The main object of my preliminary is to determine what 1 wriggle is and to decide how often and over what range to take my measurements. Results of preliminary:
From this I have decided that I am going to take the temperature for 1 minute and I will count as 1 wriggle a movement from side to side as follows:
Safety
The main safety concern in this experiment comes from the hot water used to heat us the maggot. To minimize the risks, avoid handling anything containing the hot water.
Method
- Place 1 maggot in a test tube with gauze in the bottom as shown on the diagram
- Insulate a beaker with tin foil
- Heat water up to required temperature and pour into beaker
- Place test tube into the beaker and the start timer
- After 30 seconds start counting the amount of wriggles
- After a further minute, stop timer and record the amount of wriggles
-
Repeat for temperatures from 30°C - 60°C
- Repeat whole experiment twice
Diagram of apparatus
Measurements
Record amount of wriggles in a minute every minute. Do this for 30°C, 35°C, 40°C, 45°C, 50°C, 55°C and 60°C. Repeat experiment twice and calculate averages so as to reduce the effect of anomalous results.
Equipment list
- Maggot
- Beaker
- Test tube
- Timer
- Water
- Kettle
- Thermometer
- Tin foil
- Gauze
Fair test
To make this a fair test I am going to leave the maggot in the test tube and beaker for 30 seconds to climatize. This is to make sure that the recorded results are for the correct temperatures. I also insulated the beaker to try and keep the temperature constant throughout the 90 seconds. If possible I will also do at the experiments on the same day so that room temperature is the same and the maggots I use will all be the same age.
Obtaining evidence
Changes
I have made no changes to my original plan.
Results
Analysis of Results
Trends
I can see from my graph that my prediction was correct in that the rate of wriggle increases with the temperature. Then it stays at a constant for approximately 10°C and by 60°C almost all wriggling had stopped due to the denaturing of the enzymes. This is because when the substrates become hotter, they move faster. This means that the substrate collides with the enzyme more frequently and therefore more reactions occur. At around 38°C the enzymes reach their optimum temperature. At any temperature above this, the proteins in the enzymes begin to change shape and denature. This means that the substrate will no longer fit into the active site and the reaction cannot be completed. If the reaction cannot be completed then respiration will not take place and no energy can be converted and therefore the maggot wriggles less and less until it finally stops.
Obtaining Evidence
Problems
The main problem I faced whilst doing this experiment was keeping the water and the maggot at the correct temperature. Apart from this problem which I did predict would happen and therefore I used insulation, there were no other problems.
Anomalous results
The most obvious anomalous result is for °C. This drop in rate of wriggle did not fit the line of best fit I had drawn as the amount of wriggles was less than it should have been at that temperature. This may be for many reasons. Possibly because the maggot we used was different to the rest, or the room temperature may have dropped and therefore the temperature of the water and the maggot would have dropped faster than it did for the rest of the experiments
Possible changes to plan
If I were to do this experiment again I would use a water bath instead of a beaker full of water, as it is much more accurate in keeping the temperature constant. I would also make sure all the experiments were done on the same day so as to keep room temperature as stable as possible. I would also use temperatures closer together between
35°C and 55°C so I could get an accurate curve on the top of the graph.
I could have done this experiment many different ways - Including timing how long it took to reach a certain amount of wriggles at different temperatures, or counting wriggles every 10 seconds for a minute. All of these would back up the work that I have done and the conclusions I have come to.