[Music] partial pressure of gases is the key behind their exchange in the body this is what we've learned so far but it's the process as easy as it seems for us from what we've studied so far the process is simple RBC's grab the oxygen that diffuses in the bloodstream from alveoli and pass it to the cells inversely carbon dioxide gets in the RBC's to bind with the hemoglobin and gets transported to the lungs but trust me the processes are not that simple any idea how the binding takes place how do the molecules bind to hemoglobin
what happens after the binding and what happens when the bonds are broken to deliver the respective molecules at the respective sites let's answer all these queries in this video let's begin with what happens in the alveoli here the partial pressure of oxygen is greater than that of carbon dioxide does the carbon dioxide molecules are made to leave the hemoglobin and oxygen occupies the place each oxygen binds to the iron component that is the heme group of the hemoglobin molecule thus a single hemoglobin can usually carry four oxygen molecules the binding of oxygen to hemoglobin helps
in the formation of a complex called the oxyhemoglobin but this complex formation is not very easy factors like temperature hydrogen ion concentration and also the concentration of carbon dioxide molecules around influence the binding of the oxygen along with this there is one more factor that accounts for the binding it's the structure of the binding site we note that the structure of a molecule changes as it binds to any other atom or molecule so here when the iron group binds to the carbon dioxide the shape of the protein changes reversibly now when the oxygen is about
to bind the change of shape has to be reversed so this is one more influential factor for The Binding of oxygen after all the factors approve oxygen molecules bind to the iron group and form the complex of oxyhemoglobin this is then taken to the cells where the oxygen dissociates due to increase in the partial pressure compared to that in the cells the cells on the other hand have a higher partial pressure of carbon dioxide so now imagine a scenario where the partial pressure of oxygen is lower in cells and higher in the RBC and at
the same time the partial pressure of carbon dioxide is high in the cells and extremely less in the RBC's it's obvious that the oxygen molecules will dissociate and get into the cells does the oxyhemoglobin structure will get disrupted and the hemoglobin protein will again get altered now it's all set to receive carbon dioxide molecules for which it has equal affinity the binding of carbon dioxide leads to the formation of another complex named the carb amino hemoglobin this is then carried to the lungs where the partial pressure of carbon dioxide is still lower and here the
scene is totally reversed now the partial pressure of carbon dioxide is higher than that of oxygen in the RBC's in contrast to the cells as seen earlier and the partial pressure of oxygen is lower in the RBC's compared to the lungs so the exchange and complex formation takes place once again this is how the gases are transported so are oxygen and carbon dioxide always carried in the form of these two complexes throughout the body well not exactly there is a lot more to know in this a lot of oxygen approximately more than 95 percent is
transported by the are PCs the remaining amount is transported by the plasma as oxygen dissolves in it easily and the story of carbon dioxide is totally different there is an interesting twist here hardly 20 to 23 percent of when dioxide is carried in the form of carbon Meno hemoglobin hold on did I just say around 23% only then what about the remaining amount how is so much of carbon dioxide transported then well carbon dioxide is mainly transported through the plasma this occurs in two forms around 7% is carried as dissolved solution in the plasma and
the remaining 70% is carried in the form of bicarbonate the conversion of carbon dioxide into bicarbonate is carried out by the enzyme carbonic anhydrase this enzyme converts carbon dioxide and water to give bicarbonate and hydrogen ions and where does this happen the conversion and the transport are all carried out in the RBC itself that's right the enzyme is present in the RBC and converts the carbon dioxide and water reversibly in bicarbonate and hydrogen ions so the majority of the carbon dioxide is transported in the form of bicarbonate but we do not exile bicarbonates so how
does the system work how is carbon dioxide made available during exhalation well the simple answer is reconversion the bicarbonate and the hydrogen ion produced are converted back to carbon dioxide and water as the RBC's reach the alveoli this is performed by the same enzyme carbonic anhydrase in a nutshell majority of oxygen is transported by binding to the hemoglobin protein on the other hand carbon dioxide is transported mostly in the form of bicarbonate in the RBC's and the remaining in the form of carbon we know hemoglobin in the RBC and dissolved carbon dioxide in the plasma
this is how transport of the two gases is carried out now if we plot a graph of partial pressure of oxygen against the percent saturation of hemoglobin with oxygen then a sigmoid curve is obtained this is called the oxygen dissociation curve and is this really very useful well it has a significant role to play in the study of several factors that affect breathing but we will discuss about this graph in detail in the higher grades for now let's get back to respiration and learn some more interesting facts about it meet you in the next video
until then do subscribe to our channel happy learning you
