Scenario:
Imagine you are a researcher that has recently completed an experiment intended to determine the oxygen saturation of haemoglobin in Loxodonta africana africana (African savanna elephant) blood at varying partial pressures of oxygen. You are aware of previous research performed on blood from Tamias striatus (Eastern chipmunk), which showed that an increase in PO2 leads to an increase in the percent oxygen saturation of Hb and yielded mean P50 values of 18.1 ± 1.9 mmHg (PCO2 = 40 mmHg) and 70.4 ± 4.6 mmHg
(PCO2 = 80 mmHg) (Wang 2019).
Since these are both terrestrial air-breathing animals, you hypothesize that Loxodonta africana africana hemoglobin will also (1) show a correlation between an increase in percent oxygen saturation and increasing PO2 , and (2) will exhibit similar P50 values (assume that only Tamias striatus data is currently available) at PCO2 = 40 mmHg and PCO2 = 80 mmHg.
The atmospheric pressure in your research Lab is 745 mmHg, and the temperature is 24°C. After performing 10 trials of each condition (varying %O 2 and %CO 2 (PCO2 ) in the gas mixture), you obtain the following results:
Table 1. Oxygen saturation values determined for Loxodonta africana africana blood.
Condition# could
P CO2
(mmHg) % O 2
% O2 bound*
Saturation
SD*
Saturation
P O2* @
(mmHg)
80 3 31.2 6.3 21.7
80 5 48.1 7.5 36.1
80 7 66.2 6.3 50.6
40 21 94.8 1.5 151.7
40 10 93.6 1.8 72.3
40 7 91.3 2.3 50.6
40 5 85.8 3.5 36.1
40 3 61.2 9.4 21.7
40 2 37.5 10.1 14.5
40 1.5 34.1 10.0 10.9
40 1 32.3 4.0 7.23
* n = 10; #, P CO2 = 40 mmHg (≅ 5% CO 2), P CO2 = 80 mmHg (≅ 10% CO 2); @ calculated from formulas provided in the Lab 2 manual
From the data provided in Table 1, you begin to prepare your results section for publication in a scientific journal. You start by preparing the following figure illustrating the above-summarized data:
Figure 1. Oxygen equilibrium curves of
Loxodonta africana africana blood with exposure to P CO2 = 40 mmHg
(♦) and P CO2 = 80 mmHg ( ). Symbols represent mean ± standard deviation, n=10. Note: the
80 mmHg P CO2 curve would show a sigmoidal shape if we had collected data points below 3%
O 2 and above 7% O 2.
Reflecting on this figure, prepare the discussion section of the manuscript in which you would be presenting this data. You should use your textbook, the BIO271 Pre-lab 2 manual, and Gakpo (2022) as sources, and each must be cited in your text. Your written discussion section should be a maximum of one-page double-spaced 12pt font with standard margins. Do not include Tables or Figures.
Pre-lab 2 assignment
Name: _____________________ Student ID: _____________________
Lab section: ______________________ Date due: _____________________
Name of Lab partner(s):__________________________________________________
1. Discussion [24 marks]. Note: your references section should be on a second page with your answer to question 2-4 below.
2. Recall the Pre-lab 2 demonstration and consider the carbonic acid-bicarbonate buffer system. Write out the complete equation for the reaction taking place in the beakers (do not include NaOH or Phenol red in your equation). [1 mark]
3. Briefly describe/present the two mechanisms inside red blood cells that prevent the intracellular space from becoming too acidic. [2 marks]
4. What change(s) would you expect to see in the oxygen equilibrium curve for whole human blood if we experimentally increased the concentration of 2,3-DPG in the red blood cells. How might this affect oxygen unloading at the tissues? [2 marks]
