AP151 LEC Short Essays 5

AP151 LEC

Can you explain the oxyhemoglobin dissociation curve? Can you describe how this changes with regard to changes in pH, temperature, and 2,3-DPG, and what does this mean in regard to oxygen unloading? In regard to pH, temperature, and 2,3-DPG, what would cause a right and left shift of eh oxyhemoglobin dissociation curve?  

The oxyhemoglobin dissociation curve shows the relationship between PO2 and hemoglobin saturation. A right shift occurs with decreased pH, increased temperature, or increased 2,3-DPG, which promotes oxygen unloading to tissues. A left shift occurs with increased pH, decreased temperature, or decreased 2,3-DPG, which makes hemoglobin hold oxygen more tightly. These shifts allow hemoglobin to adjust oxygen delivery based on tissue needs. Therefore, changes in pH, temperature, and 2,3-DPG regulate how easily oxygen is released from hemoglobin.

How would the nephron respond to acidosis and alkalosis in the blood? How is bicarbonate reabsorbed in the nephron? Can you describe the process? 

Normally, 80–90% of filtered bicarbonate is reabsorbed in the proximal tubule. Proximal tubule cells secrete H+ using Na+/H+ pumps, and the secreted H+ combines with bicarbonate in the filtrate. Apical carbonic anhydrase converts H+ and bicarbonate into CO2 and H2O, which diffuse into the cell. Cytoplasmic carbonic anhydrase converts CO2 and H2O back into bicarbonate, which is reabsorbed into the blood. During acidosis, more H+ is secreted, and more bicarbonate is produced to buffer blood pH, while in alkalosis, less H+ is secreted, so less bicarbonate is reabsorbed.

Can you describe the different ways in which carbon dioxide is transported? Can you describe the events of the chloride shift? Can you describe the events of the reverse chloride shift? How do levels of various molecules affect the direction in which these reactions occur? 

Carbon dioxide is transported in the blood as dissolved CO2, carbaminohemoglobin, and bicarbonate ions. In tissues, CO2 reacts with water in red blood cells to form bicarbonate and H+, and chloride ions move into the red blood cells in a process called the chloride shift. In the lungs, oxygen binds to hemoglobin, forming oxyhemoglobin, which has a lower affinity for H+, causing H+ to combine with bicarbonate to form CO2. This causes chloride ions to move out of the red blood cells, allowing CO2 to diffuse into the alveoli in a process called reverse chloride shift. The direction of these reactions depends on CO2, O2, H+, and bicarbonate concentrations, ensuring efficient CO2 transport and release while maintaining blood pH.

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