Factors affecting activities of enzymes in the body


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 (Hanzhang, 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 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 enzyme’s activity. 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 life, 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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The high amounts of CO2 in the body leads to increased pH. The lower pH indicates that the medium is acidic. Since acid has effects on the enzymes activities, the lower the pH the lower the enzyme activities. When the amount of CO2 reduces, the acidity decreases. The reduced acidity makes the medium to have more solutes and hence it withdraws water from the enzymes leading to their dehydration. The enzymes cannot work better at these pHs contributed by the increased carbon (IV) oxide.


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 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 metabolic rate. In order to determine the metabolic rates in 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 affects the metabolic rates. Very high amounts of CO2 make the medium acidic and hence denature the enzymes and so reduction in metabolic processes (Aching’, 2009). The experiment is therefore relevant with metabolic rates 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 die to the errors made in 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. 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 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.



This experiment was designed and conducted to find out how the changes in the amount of CO2 produced and the temperature as any change in the environment of the enzyme would affect the enzyme activities. It was carried out for a total of sixty seconds with the measurements taken and recorded after every six seconds. After which, a series of similar experiment was conducted as the amount of CO2 increased and the levels increased to 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 Question before and after the exercise differs due to the changes in amounts of O2 and CO2 consumed and produced. Before the exercise, less oxygen was consumed and so less expired due to low metabolic rates. After the exercise, the rate of metabolism increased and there was a need to consume more oxygen and expires more CO2.

If 21% of oxygen is inhaled and 16% is exhaled, that means 5% of oxygen is used.

RQ (before) = 4.2/5

RQ before exercise = 0.8440

RQ after exercise is =5.10/5 = 1.02. During the exercise, the body needs a lot of energy and so increased consumption of oxygen to increase energy. The amount of CO2 produced increase (for example before exercise the amount of CO2 produced was 4.2% but after exercise, the value rose to 5.1%). The body needs a lot of energy after or during exercise and hence the increase in the respiratory quotient. During exercise, nearly all proteins in the body are respired to produce energy and it happens that some fats are respired as well. Since the amount of CO2 exhaled increases during the exercise, and since RQ is directly proportional to CO2 produced, hence increase in the respiratory quotient. The amount of energy produced increases. The respiratory quotient is directly proportional to amount of energy produced.


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


Metabolic rate =  = 8.23

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  


Graph showing the amounts of CO2 exhaled against time

The red loine shows the behaviour of the amounts of CO2 exhaled after exercise while the bule show the amounts of CO2 exhaled for a resting person. The garph of the amounts of CO2 exhaled increaseses teadily and then starts dropping. During the exercise, the body needed a lot of energy and hence increase in the metabolic rates that in trun lead to increasec production of CO2. After the exercise, the amount of enegy needed gradually decaresed and this reverse the process. The amount of consumed Oxygen decreased and hence the decarese in the amounts of produced CO2.


Table 1.3

                                           CO2 produced at resting/exercise
Volume of O2 expired (L)        18.92/18.285
Volume of CO2 expired (L)        4.62/5.865


The table 1.5 showing the result of expired oxygen

Time (sec) Resting o2 Exercise o2
0 0.044 0.263
6 0.043 0.339
12 0.042 0.383
18 0.042 0.401
24 0.044 0.441
30 0.044 0.541
36 0.044 0.587
42 0.046 0.586
48 0.045 0.592
54 0.046 0.634
60 0.046 0.664

The oxygen consumed by the resting person remains constant but varies due to environmental and body factors. Due to the increased amount of energy needed after and during the exercise, the amount of oxygen consumed increased and so the amount expired. The graph of the amount of oxygen expired by the person under exercise increase while for the resting person nearly remains constant.



From the experiment, it can be found out that the optimum temperatures and amount of CO2 produce when there is a normal or when the person is resting nearly remains constant. Both internal and external temperatures have effects on the metabolic rates of an organism. When an organism is exposed to cold environment, the body reacts by increasing the metabolic rate to supply the extra heat needed to maintain the body’s internal temperature (Jorge, 2010). Exercise increased metabolic rates and so increase in body temperature. The higher temperatures in turn increased the enzyme activities. Short exposure to high temperatures has less impact on the body’s metabolism as it is compensated by increase in the heat lost to the environment form the body. When an organism is exposed to heat for long the metabolic rate increases.


Enzymes, therefore, have an optimum temperature of about 37 degrees Celsius and a pH level of about 7 and this is obtained when the body is at rest. 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 (Westerterp, 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 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.


Enzymes are protein-based biological catalysts needed by human body cells to speed up chemical reactions and are affected by temperature variances (Jorge, 2010). Their roles range from speeding up chemical reactions in the cells to ridding off waste products from the cells. Enzymes speed up all chemical reactions that take place in cells of human body. Metabolic enzymes speed up conversion of the digested food into new body structures such as flesh, muscle, nerves, glands and bones with the release on energy.


With enzyme-catalyzed reactions, although the rate at which the reaction comes to equilibrium increases with temperatures, there is a second effect of temperatures; denaturation of the enzyme protein, leading to irreversible loss of activity. However, dipping the hands in water of 400C cannot denature the enzymes and so the possibility of the experiment. The hands were thus never burnt or harmed.


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 (Hanzhang, 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 (McKay, 2009).



From the experiment conducted, it is possible to note that the amount of CO2 produced effect on the enzymes activity and this also confirms the results. Though the results in this particular experiment were not as drastic as expected, it shows the highest activity of the enzymes occur when the body is under exercise. When the person starts doing exercise, the amount of oxygen and carbon (IV) oxide produced increases. This is an indication that when more energy is needed, a person has to consume much oxygen for all the metabolic processes.  The results obtained when considering oxygen gave the results that confirmed the results. The experiment concerning the temperature changes were far off the expected results (Jorge, 2010). 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 the body metabolic activities. These metabolic activities are very crucial in the body functionality and maintenance of the 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 (Westerterp, 2001). 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 (McKay, 2009). 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 (Westerterp, 2001).

Health is a condition of complete bodily, psychological, and social welfare and not simply the absence of frailty or disease. Several avenues are available to realize this state and they all work together including temperature plus other factors. Health is very important and yet individual health is something a lot of people ignore or even neglect. The important principles to supporting good health is by Learning more concerning your health, increasing knowledge of your own situation and living a reasonable life. The experiment is vital as it helps illustrate the amount of work that one person can be able to do and the temperatures.

Today, nursing gives broadening scope of chance for skilled service and development. The trend is not to move towards what is sentimental or traditional but rather to what is meaningful and practical.  There are three major relations that are well-known such as the patients surrounding, nurse’s environment and the nurse to the client (McKay, 2009). For instance the requirement for light, temperature in particular is second only to the requirement for aeration. If essential the nurse ought to move the client above after the sun in accordance to the features of the rooms, if situations allow, than let him remain in a room when the sun is off. The experiment helps in determining the correct and appropriate temperature that will not denature the enzymes in the hospital rooms (Jorge, 2010).

The patients need to know the issues relating to their metabolic rates, weight and cholesterol management and other issues related to diabetes. It is thus the big role of nurses to guide their patients in lifestyle modification and change from the authoritative and instructive traditional methods of relating with medical practitioners educating them on how to manage the chronic diseases (McKay, 2009). It has been noted that the best way to manage the diseases is by involving the patients in the important choices that have to be made as compared to forcing ideas into their lives because chances are that they will not be part of the exercise as it does not make sense to them. Nurses and other physicians are of the idea that patients have a responsibility of making lifestyle decisions that affect their health but they would not know exactly what is expected of them unless they are taken through the basics of understanding their role and responsibilities through health counseling.


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 (Westerterp, 2001).
  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.

McKay, M. (2009). Effects of spinal anaesthesia on resting metabolic rate and quadriceps mechanomyography. Springer-Verlag, 25 March 2009 / Published online.



Westerterp, K. (2001). Limits to sustainable human metabolic rate. Department of Human Biology, Maastricht University.



Hanzhang L. et al. (2010). Alterations in Cerebral Metabolic Rate and Blood Supply across the Adult Lifespan. Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.



Jorge S. (2010). Understanding the energetic costs of living in saline environments: effects of salinity on basal metabolic rate, body mass and daily energy consumption of a long-distance migratory shorebird. The University of Extremadura.


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