Factors influencing the activities of Enzymes


The bodies of living things are composed of cells. The cells do undergo the body metabolic activities which are very fundamental for the maintenance of the life of the living thing (Hawks, 2006). Metabolic rate is defined as the amount of energy an organism consumes within a given time. The metabolic reactions in the body need to be sped up by the actions of the enzymes present in the body cells. However, metabolic rates are dependent on various factors like temperature, pH, and amount of food among others. In many cases, the functions of the enzymes have been faced with various environmental conditions which then affect their final efficiency and outcome. This experiment is therefore conducted to make out the effects of the variations in the level of temperature on the actions of the activity of the enzyme. Since the rate of enzyme action is dependent on the metabolic rate, the experiment directly determines metabolic rates.


Enzymes are organic materials found within the living cells of the body to majorly act as the catalysts to the body chemical reactions. The major work of the enzymes in the body is to catalyze the rates of reactions which take place in the body, though they do not take part in such chemical reactions, that is, they are not used chemically in the reactions hence they are special kinds of organic materials. The living cells in the body are ever undergoing chemical changes so as to remain a live, and the work of these enzymes is to ensure that there is low activation energy for the body reactions so as to make the reactions run faster. Higher CO2 levels confirm that there is increased metabolic rate and lower CO2 confirms the reverse.

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This experiment is therefore carried out to make out the factors which may influence the activities of the enzymes in their work of catalyzing the rates of reactions in the body. The major focus is placed on the effects of changes on the temperature in the environment of the enzymes affects their activity. There are various ways of determining the rate of metabolic rates in the body including the rate at which oxygen is consumed in the body.

The amount of CO2 was measured and translated to be the pH since CO2 is acidic. Knowing the total volume of air breathed, the time taken, and the concentration of CO2 it was easy to calculate the metabolic rate. In order to determine the metabolic rates in a different person, the various amounts of CO2 produced were examined. It is evident that CO2 produced and metabolic rates are directly proportional. When CO2 is increased, the acidity of the solution is increased and so reduced pH. Very low pH denatures the enzymes and so reduction in metabolic processes (Aching’, 2005). The experiment is therefore relevant with pH and temperature used to measure the metabolic rates of different persons. The tabulation of the amount of carbon (IV) oxide and oxygen exhaled during the process was important as it assisted in determining the metabolic rates directly. The results are confirmed using pH and temperatures in measuring the metabolic rates.

The basal metabolic rate is expressed as kcal/m2 of body surface area/hour calculated as


The experiments were done by varying the conditions and temperatures and subjecting the enzymes to the changes in the conditions. The experiment showed that the enzyme actions are most active at the pH close to seven which is relatively the closer pH of the body. Extremes of pH lower the levels of enzyme activity. Temperature experiment, however, did not show the expected results possibly due to the errors made in the making of the experiment samples and arrangements or reading of the experiment scores.

 The valve-mouthpiece was connected to Douglas bag so that you inspire atmospheric air and expire into the Douglas bag


  1. The bags were breathed into until they were full
  2. The volume of expired in was measured using “gas meter”. The volume of CO2 exhaled was determined of a time interval of 60 seconds. The results are recoded in table 1.2.
  3. A representative sample was taken into a small sample bag and the proportion of oxygen in the inspired air was measured
  4. The procedure was repeated with persons exercising vigorously for 5 minutes
  5. The amount of CO2 was measured for a period of 60 minutes from exercise and during rest. The results are tabulated in the following table.

In determining pH and Temperatures, the following material were used


  1. Colorimeter
  2. Bottle of distilled water
  3. Bottle of turnip extract
  4. Bottle of substrate mix
  5. Cuvettes for colorimeter
  6. Pipetter (green for 5-10 ml pipettes)
  7. Pipetters (5 ml)
  8. Micropipette (100-1000 µl) and tips
  9. Box of kim-wipes



This experiment was designed and conducted to find out how the changes in the pH and the temperature in the environment of the enzyme would affect the enzyme activity. It was carried out for a total of sixty seconds with the measurements taken and recorded every three seconds. After which, a series of similar experiment was conducted as the pH adjusted to the levels of 2, 7, and 10 and temperature was adjusted to 4°C, 22°C, and 37°C.



Table 1.0

  Before  exercise After exercise
Time (min) 3 3
No of breath (per min) 16 30
Volume of expired air (L) 110 115
% of O2 in expired air 17.20 15.90
% of CO2 in expired air 4.2 5.10
Volume of O2 expired (L) 18.92






Volume of CO2 expired (L) 4.62






O2 atmosphere 19.60%
CO2 atmosphere 1.50%
N2 atmosphere 78.9%



Body surface area 2.30 m2


RQ =

Respiratory quotient is for before exercise is 0.24 and after exercise is 0.32.



Metabolic rate =  = 8.23


Experimental Setup for Temperature

Table 1.1

Temperature Distilled Water Turnip Extract Substrate Mix Total
Ice Water 4°C 2.2 ml 400 µl 400 µl 3.0 ml
Room Temp. 22°C 2.2 ml 400 µl 400 µl 3.0 ml
Body Temp. 37°C 9resting person) 2.2 ml 400 µl 400 µl 3.0 ml


CO2 levels on the person immediately after exercise

Table 1.2

Time (secs) Resting person Exercising persons  
0 0.626 0.263  
6 0.629 0.524  
12 0.682 0.744  
18 0.699 0.916  
24 0.651 1.048  
30 0.613 1.150  
36 0.671 1.229  
42 0.623 1.295  
48 0.667 1.356  
54 0.607 1.410  
60 0.647 1.464  


Table 1.3


pH Reaction Rate (slope):
4°C .33/60
22°C 0.771/60
37°C 1.201/60


Experimental Setup for pH Experiment

Table 1.4

Temperature Amount of Buffer Turnip Extract Substrate Mix Total
pH 2 buffer 2.2 ml 400 µl 400 µl 3.0 ml
pH 7 buffer 2.2 ml 400 µl 400 µl 3.0 ml
pH 10 buffer 2.2 ml 400 µl 400 µl 3.0 ml


Absorbance Results for Various pH Buffer Reactions

Table 1.5

Time (secs) pH 2 pH 7 pH 10
0 0.044 0.268 0.000
6 0.043 0.359 0.000
12 0.042 0.443 0.000
18 0.042 0.521 0.000
24 0.042 0.591 0.000
30 0.044 0.651 0.000
36 0.044 0.707 0.000
42 0.046 0.763 0.000
48 0.045 0.812 0.000
54 0.046 0.859 0.000
60 0.046 0.904 0.000


Table 1.6

pH Reaction Rate (slope):
pH 2 .416/60
pH 7 .636/60
pH 10 .000/60



From the experiment, it can be deduced that the optimum temperatures and the pH for the enzyme to function is similar to the normal body temperature and pH. Enzymes, therefore, have an optimum temperature of about 37 degrees Celsius and a pH level of about 7. This is evident with the person resting as opposed to the person exercising. These are the conditions commonly considered to be the Norman conditions and are generally referred to as the standard conditions for the enzyme activity (Madsen, 2006). It is also important to note that drastic change in the pH and temperatures level can deform the enzyme and make then nonfunctional.


After exercise, the temperature increased. Since enzymes are dependent on the temperature. The increased temperature increased their activities in the body. More food was broken down and so the need for excess oxygen and thus CO2 produced also increased. This is evident with the second person (after going through the exercise) that his level of CO2 increased from 0.263 to 1.464 over a period of 60 seconds. On the contrary, the amount of CO2 produced by the resting person fairly remained constant. Though there existed fluctuation but that might have been contributed by various factors like change in temperature (atmospheric) among other factors. The result, therefore, confirms that increased temperature has effects on pH and therefore metabolic rates.


The enzymes in the body have special shapes and always work on and changes specific substances called the substrates. During the time of the chemical change of the substrates, enzymes must come into contact with them at the places called the active sites (Hawks, 2006). It is important to note that the substrate and the enzyme must have conformity in their structures and shapes so that they fit well into one another for efficient changes. Once the change of the substrate is complete, the enzyme is detached from the substrate and regains its original shape ready for a new substrate. This means that in most cases, enzymes are reusable and are very adaptable to the substrates (Aching’, 2005).



From the experiment conducted, it is possible to note that the pH effect on the enzyme’s activity confirms the results. Though the results in this particular experiment were not as drastic as expected, it shows the highest activity of the enzymes at the pH of 7 which is almost similar to the body pH (Aching’, 2005). However, the results for the temperatures experiment did not give the results expected at all. The experiment concerning the temperature changes were far off the expected results. The wide deviations of the temperature results of the experiment from what is normally expected can be attributed to human errors which might have been incurred during the conduction of the experiments in the laboratory and in making the samples.


It cannot be disputed that enzymes are very important for all body metabolic activities. These metabolic activities are very crucial in the body functionality and maintenance of life. Given the right conditions of temperatures and the pH, enzymes reduce the activation barrier between them and the substrates. They thus come into contact with the substrate and amicably change them but they remain unchanged (Madsen, 2006). Provision of diverse conditions of temperature and pH, however, leads to the deformation of the shapes of the enzymes and as a result, they would not be able to come in to close contact with the substrate to change them.

The gist concept of this experiment is to bring about the correlation between the enzyme activity and the changes in the enzyme environment. A close focus in placed on the particular effects of the pH and temperature influences on the enzyme activity. The fact that enzymes are found within the body of the living things, the effects of temperature and pH on the enzyme activity would reveal a close correlation of the possible effects the body is likely to undergo whenever it is exposed to the extreme and diverse cases of pH and environmental changes (Madsen, 2006).

 Limitations of the experimental procedure and the calculations

  1. The study is limited to two people, the resting and the person after exercising.
  2. The measurements were never accurate of had low accuracy levels. The relation between the amounts of air breathed out and in might not directly depend on the metabolic rate of the organism. The relation might depend on other factors as well but in this case, it is assumed that they are directly proportional (Madsen, 2006).
  3. Rounding off reduced the accuracy of the data obtained. Most data were either rounded off or truncated and this reduces the result accuracy.
  4. The experiment lacked control. It is expected that other factors must have affected the experiment and the control measures were never taken into consideration. This is to say that the experiment must have been affected by external factors. However, with the reference, it can be assumed that similar factors affected both the two persons and so their effects neutralized.


Aching’, A. (2005). Nursing a human need approach. Lippincot publications.

Hawks, J., (2006). Surgical Medical Nursing. 6th ed. Elsevier Mosby Publications: Philadelphia.

Madsen, W. (2006). Nursing History Foundations of a Profession, 2nd ‘edn’. Pearson Sprint Print, Australia.


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