Gas Exchange in the Lungs
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
As the tissue is low, oxygen diffuses down the partial pressure gradient and out of the blood. The blood falls, and oxygen is released from haemoglobin into physical solution. The process continues until adequate oxygen has been released from the blood for aerobic metabolism (each 100 mL of blood loses 5 mL of oxygen, and the falls from 100 to 40 mmHg [13.3 to 5.3 kPa]). The gradient from the blood to the tissues is maintained by the steep part of the oxygen–haemoglobin dissociation curve as blood tends to be maintained while oxygen is lost. The higher tissue , temperature and hydrogen ion concentration encourage oxygen release by haemoglobin via the Bohr effect.
Applied exercise physiology and the environment
Nick Draper, Helen Marshall in Exercise Physiology, 2014
In addition to PO2, the oxygen saturation of haemoglobin is affected by blood pH (acidity), blood temperature, and 2,3-diphosphoglycerate (2,3-DPG). A decrease in blood pH (rise in acidity) or an increase in body temperature weakens the bond between oxygen and haemoglobin, hence an increased offloading of oxygen at the tissues occurs. This reduction in the affinity of haemoglobin for oxygen is represented by a rightward shift of the oxyhaemoglobin curve and is known as the Bohr effect. During strenuous exercise, pH falls (due to the rise in lactate and associated rise in H +) and body temperature increases above 37°C (due to muscular heat production). As such, exercise can shift the curve to the right, facilitating the offloading of oxygen to the tissues where it is required, particularly skeletal muscle.
Physiology of the respiratory system
Louis-Philippe Boulet in Applied Respiratory Pathophysiology, 2017
A small volume of CO2 is carried in the plasma, where it binds to proteins. CO2 interacts with an amino group. A protein that carries CO2 is called carbamino group. Two percent of CO2 is transported this way. CO2 may also combine with the globin protein on hemoglobin to make a carbamino-hemoglobin group. This binding between CO2 and hemoglobin takes place on different sites than for oxygen, which binds to the heme component of hemoglobin. The hemoglobin affinity for CO2 increases when the quantity of oxygen binding to hemoglobin decreases, which means that desaturated hemoglobin has a higher affinity for a given PaCO2 (Haldane effect). Conversely, hemoglobin that carries CO2 has less affinity for oxygen (Bohr effect). Ten percent of CO2 is carried as carbamino-hemoglobin groups.
Interaction of 17β-estradiol and dietary fatty acids on energy and glucose homeostasis in female mice
Published in Nutritional Neuroscience, 2018
Kyle J. Mamounis, Michelle R. Hernandez, Nicholas Margolies, Ali Yasrebi, Troy A. Roepke
The presence of higher circulating and tissue FAs in HFD-fed mice is supported by their reduced CO2 production. A reduction in CO2 production, particularly in the presence of a relatively stable O2 consumption, indicates an increased ratio of FAs as energy substrate. Respiratory quotient, CO2/O2, has also been used as an independent predictor of body mass changes.47 There is evidence from the basic chemistry of the Bohr effect on hemoglobin,48 as well as the hypercapnic activation of vitamin K2-dependent enzymes,49 that CO2 supports the metabolic rate. Boulder and other high altitude cities50 have substantially lower rates of obesity and associated metabolic disease. Since a low-fat, glucose-based metabolism has the same effect on capnia, or blood CO2 level, as altitude, this seems like a more obvious place to start in explaining low obesity rates common in high altitude populations than their idiosyncratic diets and cultures.
CO2 permeability of the rat erythrocyte membrane and its inhibition
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Samer Al-Samir, Maximilian Prill, Claudiu T. Supuran, Gerolf Gros, Volker Endeward
We report here an intraerythrocytic carbonic anhydrase activity of 64,100, which may be compared with the value of 21,000 we obtained for human red cells with the same method under identical conditions4. Thus, rat red cells have a 3 times higher Ai compared to human red cells. While the absolute numbers of these activities cannot be compared with the results obtained by Larimer and Schmidt-Nielsen19 due to highly different methods and conditions, it may be noted that these authors similarly found a 2.5 times higher Ai in rats compared to humans. In general, these authors observed a tendency of Ai to increase with decreasing body weight in mammals. The functional significance of the higher Ai values in smaller animals is not clear. Larimer and Schmidt-Nielsen speculated that the high carbonic anhydrase activity in small animals with their higher specific rate of oxygen consumption may improve oxygen release from red cells by an accelerated production of H+ from CO2, thus accelerating the contribution of the Bohr effect to O2 release19. Their studies have been discussed and updated in a more recent review20.
Hb Q-Thailand heterozygosity unlinked with the (–α4.2/) α+-thalassemia deletion allele identified by long-read SMRT sequencing: hematological and molecular analyses
Published in Hematology, 2023
Danqing Qin, Jicheng Wang, Cuize Yao, Xiuqin Bao, Jie Liang, Li Du
Hb Q-Thailand is a slow-moving abnormal hemoglobin that is characterized by a substitution of aspartic acid with histidine at the 74th position of the normal α1-globin chain. This hemoglobin shows normal oxygen affinity, a normal Bohr effect and normal cooperativity because the substituted amino acid is nonfunctional [8]. It was first observed in 1958 by Vella et al. in Singapore and first discovered in the Chinese population in 1983 by Zeng et al. [9,10]. Hb Q-Thailand has a high detection rate in southern China and Southeast Asian countries, where it occurs mostly in a heterozygous or compound heterozygous state with α0-thalassemia, causing Hb Q-H disease [3,4,8,11–13]. Although Hb Q-Thailand has been found in various populations, the present study is the first to report a negative result for DNA analysis of the (–α4.2/) deletion.
Related Knowledge Centers
- Bicarbonate
- Carbon Dioxide
- Carbonic Acid
- Carbonic Anhydrase
- Exhalation
- Ph
- Lung
- Hemoglobin
- Red Blood Cell
- Oxygen–Hemoglobin Dissociation Curve