Question

Respiratory alkalosis leads to a shift of hemoglobin to the active R state. At first, it may be unclear why shifting to the R state is a bad thing, but the reason should be clear shortly. First, let us examine how CO, also affects hemoglobin directly. CO2 has a direct effect on hemoglobin In addition to its indirect effect on hemoglobin structure through its effect on pH, CO, also directly affects hemoglobin by reacting with the amino-terminal residue of each of hemoglobin's polypeptide chains to form a carbamate group. CO, +H, N Y N The reaction with CO2 to form carbaminohemoglobin occurs more often where CO2 concentrations are high, such as in the peripheral tissues. There are two important aspects of this reaction. First, this reaction causes conformational changes that ultimately favor the T state and the release of O2. The exhalation of CO2 in the lungs favors the reversal of this reaction and the transition back to the R state. Thus, the formation of the carbamate group acts similarly to the protonation of His B146 in that it occurs at low pH and favors the T state. Second, when the CO2 concentration is high, the formation of carbamate also produces H", as shown in the reaction diagram, which decreases the pH. Conversely, when the reaction goes in the opposite direction and releases CO2, H is consumed and the pH increases. Classify each condition according to whether it favors the R state or the T state of hemoglobin. R state T state Answer Bank high pH high H concentration low CO2 concentration low pH low concentration high CO2 concentration

Answer 1

The T-state is the deoxy form of haemoglobin (meaning that it lacks an oxygen species) and is also known as "deoxyhemoglobin”.The R-state is the fully oxygenated form: "oxyhemoglobin.

R state	T state
High pH	Low pH
Low CO2 concentration	High Co2 concentration
Low H+	High H+