Effect of pH on Percent Oxygen Saturation of Haemaglobin

Effect of pH on Percent Oxygen Saturation of HaemaglobinAbstractThe purpose of this lab was to determine the outlet of changes in the pH and the uncomplete squash of group O on hemoglobins similitude for atomic number 8 and part atomic number 8 fertilization in the Bos taurus blood. At a start out pH (6.8) with a 21mmHg p50 value, it was open that the atomic number 8 dissociation curve tradeed to the right, which indicates that the Bohr Effect causes hemoglobin to miss its affinity for group O. This concludes that the affixd carbon dioxide dousing forces hemoglobin to release its bound atomic number 8 to the high metabolizing tissues (converting to deoxy- hemoglobin), nevertheless also forces the protein to concur more group O at the respiratory get ons in order to transport becoming type O to beas with a low atomic number 8 incomplete t whizz insistence. At a high pH (7.4), the type O dissociation curve shifted to the left with a 14mmHg p50 value si nce haemoglobin receives more oxygen, causing haemoglobin to put matchless across a higher affinity for oxygen and to re master(prenominal) as oxyhaemoglobin. Both sigmoid spirtd curves find out a draw portion at 9.1mmHg and a plateau at 60mmHg. In conclusion, since the p50 value at pH 6.8 (21mmHg) is lower than the p50 value at pH 7.4 (14mmHg), this signifies that in an acidic environment, in that respect is a higher partial rack of oxygen in the environment as haemoglobin can non bind the available oxygen as much due to its lowered affinity for oxygen.IntroductionHaemoglobin is a specialized protein make up inside the red blood cells of vertebrates that have developed organs for gaseous exchange as a substitute for simple diffusion. This respiratory pigment transports dissolved oxygen in the blood from the respiratory surface to the tissues through the circulatory system, and transports carbon dioxide rachis for excretion at the respiratory surface by exhalation. When one oxygen molecule binds to the iron containing heme group of the tetrameric-structured haemoglobinwhich has four globulin subunits non-covalently linked to each other(a) cardinal alpha- and dickens beta-polypeptide chainsits allosteric property increases its affinity for the addition of the adjacent trinity successive oxygen molecules (Fenton et al., 2015). A total of four oxygen molecules can bind to this protein however changes in the partial pressure of oxygen at the gas exchange site can affect haemoglobins pct oxygen vividness and changes in pH can alter haemoglobins affinity for oxygen (also known as the Bohr Effect).The magnitude of the Bohr Effect in haemoglobin results from the breaking of the salt bridges betwixt the histidine residues when the protein changes between its two structures at equilibrium oxyhaemoglobin and deoxyhaemoglobin (Kilmartin, 1974 Zheng et al., 2013). During the structural shift, the histidine residues entrust react with the sulfhydryl group o f the cysteine that is found in the deoxyhaemoglobin (Okonjo et al., 2014). Consequently, this change in the structural con shaping of cysteine leads to a reduced Bohr Effect (Okonjo et al., 2014). Since deoxyhaemoglobin has been altered at a chemical level, it allow for experience a minimized Bohr Effect while its affinity for oxygen increases (Riggs, 1988). The Bohr Effect states that in a high pH alka business concern environment, protons are released when oxygen is attached to haemoglobin but are not released when in an acidic environment (Riggs, 1988).To what extent did the variations of PO2 and pH levels affect haemoglobins per centum oxygen fecundation in the Bos taurus blood was examined as the main purpose in this lab and is depicted by an oxygen dissociation curve. The resultant sigmoidal (S) radiation diagram relates the partial pressure of oxygen and haemoglobins percent oxygen saturation at polar pH levels. Given that the manometer PO2 is held constant at the spe cific mmHg value, it is predicted that the oxygen dissociation curve will shift to the right at a pH of 6.8 (which is lower than the normal pH value of 7.4) as on that point is an increase in carbon dioxide concentration. This indicates that a pH drop will decrease the percent oxygen saturation of haemoglobin, and hence, its affinity for oxygen. Conversely, it is estimated that the curve will shift to the left at a pH of 7.4 as there are less carbon dioxide molecules in an alkaline environment. It is also predicted that at P50, there will be a difference in the percent oxygen saturation of haemoglobin at the different pH levels and that the two sigmoidal curves of the oxygen dissociation graphical record will eventually attain at equilibrium past P50 due to the Bohr Effect.In relation, Hill conducted his audition with a similar procedure on human muscle and haemoglobin and concluded that at a higher pH level (muscle haemoglobin at pH 9.2 and blood haemoglobin at pH 9.2), the curv e shifted to the left while at a lower pH level (muscle haemoglobin at pH 7.0 and blood haemoglobin at pH 7.0), the curve shifted to the right due to the Bohr Effect (Hill, 1936).Materials and MethodsThis experiment was conducted based on the BIO202 lab manual of arms however, the procedures performed for the Bos taurus at pH 7.4 under share 2 was deviated from the instructions provided. The maximum nullity pressure was set at 750 mmHg instead of the listed value of 700mmHg since vacuum did not provide enough pressure at 700mmHg to deoxygenate the blood appropriately. My lab partners, Isabel, Zainab and Dianne, performed the experimental tests on Bos taurus buffered at pH 7.4. We self-collected the information conducted at pH 6.8 from our colleagues Kashamala, Kiran, Jing, and Seevin.ResultsFigure 1This oxygen dissociation curve graph depicts a logarithmic regression that relates the effect of the partial pressure of oxygen on haemoglobins percent oxygen saturation at both pH le vels in Bos taurus. The manometer schooling was reborn to the partial pressure of oxygen with equation a listed in the appendix. In addition, the percentage infection value obtained from the spectrophotometer was converted to the percent oxygen saturation of haemoglobin using the equations of the two logarithmic regression curves.The P50 value at pH 6.8 is 21mmHg and at pH 7.4 is 14mmHg. This value reveals the change in the partial pressure of oxygen at the different pH levels due to the Bohr Effect when 50% of haemoglobin has been saturated.In Figure 1, the effect of the partial pressure of oxygen on the percent oxygen saturation of haemoglobin illustrates a sigmoidal shape as the main trend at the pH of 6.8 and 7.4. As PO2 increases, haemoglobins oxygen saturation also increases until a maximum amount of oxygen molecules have bound to this blood pigment. There are two patterns in this oxygen dissociation graph (1) the steep (beginning at 9.1mmHg) and (2) the plateau (60mmHg).Th e steep section begins when PO2 first rises from 9.1mmHg and the percent saturation increases drastically. At pH 6.8, the steepness levels off at point three where PO2 is 30.1mmHg and the percent saturation is at 84.0826%. At pH 7.4, the steepness levels off at point two where PO2 is 30.1mmHg and the saturation is at 83.6601%.When haemoglobin has reached its maximum oxygen capacity, the curve relating PO2 and haemoglobin saturation plateaus and become theoretical. During this period, haemoglobin maintains its maximum oxygen saturation at the maximum PO2. At pH 6.8, the maximum PO2 of 156.12mmHg occurs when the vacuum is not utilize (the pressure remains at 0mmHg), which gives haemoglobin a maximum theoretical oxygen saturation of 102.612%. At pH 7.4, the maximum PO2 of 156.12mmHg gives haemoglobin a maximum oxygen saturation of 97.7172%, which is slightly lower than the value at pH 6.8.In terms of pH change (the Bohr Effect), the curve of the lower pH shifts to the right while the curve of the higher pH shifts to the left. However, the starting point for both of the sigmoidal-shaped curves is at PO2 of 9.1mmHg, where 6.9259% saturation is for pH 6.8 and 8.3333% saturation is for pH 7.4.DiscussionThe results support the hypothesis that the oxygen dissociation curve will shift to the right at the pH value of 6.8, showing that haemoglobins (Hbs) percent oxygen saturation decreases (due to a lower affinity for oxygen), whereas the graph will shift to the left at the pH value of 7.4, demonstrating that haemoglobins percent oxygen saturation increases (due to a higher affinity for oxygen). The p50 value from the graph indicates that in a basic environment, there is a lower partial pressure of oxygen in the environment (14mmHg) when compared to an acidic environment (21mmHg) because haemoglobin is able to bind to more of the available oxygen due to its increased affinity for oxygen whereas at pH 6.8, haemoglobin is unable to bind to as much oxygen due to its decreas ed affinity for oxygen. The reason behind this lowered oxygen affinity is due to the Bohr Effect and the high concentration of carbon dioxide present in the area. Moreover, the amount of carbon dioxide concentration present changes the pH, which directly affects the ability of haemoglobin to bind to oxygen and readily dissociate oxygen.When there is a high partial pressure of oxygen in an area where haemoglobin is present, the tetrameric proteins percentage saturation of oxygen increases as well because there are more available oxygen molecules to bind to. cod to the cluster of oxygen molecules around this blood pigment, haemoglobins affinity for oxygen becomes tremendously improved due to its allosteric property, where the next three successive oxygen molecules are more readily bound after the first one has been attached. From this, since haemoglobin is able to transport more oxygen molecules from the respiratory surface, a high concentration of oxygen is released into the blood plasma to be absorbed by the surrounding tissues. This is why in Figure 1, the graphcomparing the effect of the partial pressure of oxygen on haemoglobin saturationhas an incredibly steep curve at the beginning to indicate that haemoglobin is able to pick up a make out of oxygen molecules.From the graph, at pH 6.8, there is a high partial pressure of carbon dioxide where piddle reacts with carbon dioxide, generating H+ ions that produce an acidic environment with a low pH (Riggs, 1988). This reduces haemoglobins affinity for oxygen, where haemoglobin subsequently converts into deoxyhaemoglobin, which is its alternate structural form. In this acidic environment, the tissues are at a high metabolic rate and need more oxygen molecules. So, according to the Bohr Effect, haemoglobin will bind to more oxygen at the respiratory surface and release its oxygen content more readily at the tissues (where there is a lowered PO2) in order to entreat the pH level back to normal. In essence, th e body raises the partial pressure of oxygen to match that of carbon dioxide so that a projectile equilibrium is created to raise blood pH back to normal levels and reduce the acidity where the rate of perfusion and dissemination is equal to each other. In terms of the pH at 7.4, there is low carbon dioxide partial pressure where the environment is more alkaline. The Bohr Effect prevents the transport of oxygen to the deoxygenated area, so that the partial pressure of oxygen also decreases in respect to the partial pressure of carbon dioxide in an attempt to decrease the pH level. However, if haemoglobin attaches onto oxygen, protons are released, which equals out the increase in oxygen with an increase in carbon dioxide. Thus, the increase in H+ is directly proportional to the increase in CO2 (Riggs, 1988).The two curves eventually meet together at one point, indicating that Bos taurus is attempting to maintain pH equilibrium, where pH 6.8 attempts to raise Hb saturation for a m ore alkaline environment and pH 7.4 attempts to reduce Hb saturation for a more acidic environment.However, the Bohr Effect presents an advantage to the body when it is subjected to an oxygen deficient environment during exercise, where there is lactic acid buildup, a drop in blood pH, and an increase in carbon dioxide and hydrogen concentrations. The formation of carbonic acid and H+ ions from the reaction between water and carbon dioxide produces an acidic environment, lowering the pH levels (Riggs, 1988). In these regions, the production of carbon dioxide from muscle cells inhibits haemoglobins affinity for oxygen in the bloodstream by binding to haemoglobin itself, forming carbamino haemoglobin. Carbamino haemoglobin brings the H+ protons generated along with the carbon dioxide molecules to the lungs, where it is expelled through exhalation (Riggs, 1988). When this happens, there is not enough oxygen present at the tissues, so the Bohr Effect sends haemoglobin to the tissues, wh ich readily releases its oxygen content into the tissues because it can no longer hold onto the molecule as it travels further into the bloodstream. Eventually, the Bohr Effect helps to raise blood pH back up to normal levels when enduring anaerobic respiration since haemoglobin is continually releasing its bound oxygen molecules as its affinity decreases to be the rising carbon dioxide levels. It is beneficial for haemoglobin to have a low affinity for oxygen near the tissues to increase oxygen uptake by the tissues, but to have a high affinity for oxygen at respiratory surfaces so haemoglobin can transport as much oxygen as possible, and as far into the body as possible. Thus, altering the oxygen affinity of haemoglobin is the bodys way of using the Bohr Effect to its advantage to solve the difficulty of lacking oxygen since more oxygen is released with an increase in carbon dioxide levels.One limitation of the experiment involved the absence of a spectrophotometer and the instru mental error of the vacuum. The vacuum failed to serve its purpose at the 700mmHg level, so it had to be increased to the 750mmHg level for the procedure done for pH 7.4, which results in an unfair comparison for the data done for pH 6.8. In conclusion, when pH is low, haemoglobin has less affinity for oxygen (lower saturation) whereas when pH is high, haemoglobin has more affinity for oxygen (higher saturation).ReferencesFenton, B., Dumont, B., and Owen, M. (2015). Respiratory Pigments Hemoglobin andHemocyanin. In Integrative Animal Biology (ed. S. Hinic-Frlog), pp. 300-301. Toronto, ON Nelson Education Ltd.Hill, R. (1936). Oxygen Dissociation Curves of Muscle Haemoglobin. Proc. R. Soc. Lond. 120,472-483.Kilmartin, J. V. (1974). THE ALKALINE BOHR EFFECT OF HUMAN HEMOGLOBIN.Annals of the New York Academy of Sciences. 241, 465-471.Okonjo, K. O., Olatunde, A. M., Fodeke, A. A. and Babalola, J. O. (2014). Bohr effect ofhuman hemoglobin A Magnitude of negative contributions determined b y the equilibrium between two tertiary structures. Biophysical Chemistry. 190, 41-49.Riggs, A. F. (1988). The Bohr Effect. Annual Reviews Inc. 50, 181-204.Zheng, G., Schaefer, M. and Karpus, M. (2013). Hemoglobin Bohr Effects Atomic Origin of the Histidine Residue Contributions. Biochemistry. 52, 8539-8555.AppendixFigure A1This old-hat curve graph depicts a linear regression that relates the effect of percent transmittance on the percent saturation of haemoglobin at both pH levels in Bos taurus. Oxygenated haemolysate was exposed to the vacuum at a maximum pressure of 700mmHg for 5 minutes to become entirely deoxygenated, which was added to the oxygenated haemolysate. Different amounts of deoxycytidine monophosphate% oxygenated and 100% deoxygenated haemoglobin were combined to give five various saturation percentages. A percent transmittance variant was taken for each of the saturation percentages, using a spectrophotometer.Oxygen Dissociation Curve (Sample Calculation 1)The man ometer reading values are converted to the partial pressure of oxygen with the formula (Equation a), where D is the barometric pressure (measured in mmHg), W is the water vapor pressure (measured in mmHg), and M is the manometer reading (measured in mmHg). The temperature was 22C and the barometric pressure was 763mmHg for the lab room.Manometer reading at 300mmHgTherefore, the partial pressure of oxygen at a manometer reading of 300mmHg is 93.1mmHg.Oxygen Dissociation Curve (Sample Calculation 2)The regression line equation is used to convert the percent transmittance to the percent oxygen saturation of haemoglobin.At the pH 6.8The regression line equation is, where the variable y represents the percent transmittance value and the variable x represents the percent oxygen saturation of haemoglobin.Partial pressure of oxygen at 93.1mmHgTherefore, the percent oxygen saturation of haemoglobin is 98.0559% at the pH 6.8.At the pH 7.4The regression line equation is, where the variable y r epresents the percent transmittance value and the variable x represents the percent oxygen saturation of haemoglobin.Partial pressure of oxygen at 93.1mmHgTherefore, the percent oxygen saturation of haemoglobin is 94.7712% at the pH 7.4.