 Now, we talk about various factors which can affect the gas exchange. These factors are carbon dioxide, temperature, pH, carbon dioxide as we know when it is increased it actually decreases the saturation of it actually decreases the oxygen tension which result in the capacity of hemoglobin for oxygen or carrying oxygen is reduced. This result in release of oxygen molecules towards the blood. Second is temperature. Temperature if it is increased that is rise in temperature decreases the oxygen carrying capacity of the hemoglobin. So, if temperature is increased then oxygen carrying capacity of hemoglobin is decreased and hemoglobin will release oxygen and we know that the airways are sending a moist and warm air inside the lung. This warmth result in decrease in oxygen carrying capacity of hemoglobin and hemoglobin molecules releases oxygen which is then taken up by the capillaries. pH, if pH declines oxygen carrying capacity also declines. So, because actually what happened that hydrogen ions because when we know that when pH goes down actually hydrogen ions are released in solution these hydrogen ions actually bind to hemoglobin to some part of it to decrease its oxygen carrying capacity. So, if pH is decreased then oxygen carrying capacity will also the hemoglobin molecule will also decrease. Now, the lung capacity the human lungs while fully expanded have a capacity of about 5 letters, but actually when we are sleeping we are at rest lungs are only exchanging a half a liter of the air. So, very much less while exercising this capacity this exchange may increase up to 3.5 liters. It means that there is a 1.5 liter residual volume that cannot be expelled in any case. Inhalation as we know inhalation is 15 to 20 cycles per minute. If we are exercising this may increase up to 30 cycles and that is we breathe rather than 15 to 20 times per minute we breathe for 30 times per minute. So, when we are exercising then the lung then the capacity of lungs is differently utilized and in a more efficient way. So, this is about the lung capacities. Now, changes in the composition of the breathe air when we breathe air in and then this is expelled out what is the difference? This air actually we are talking about the difference of inhaled air and the exhaled air. So, that we can find out that what is the difference in the percent saturation air when it is entering inside the lungs is 21 percent saturated with oxygen when it goes out it is 16 percent saturated. So, there is a 4 percent decrease carbon dioxide is 0.04 percent saturated in the air, but when air goes out this is 4 percent saturated with carbon dioxide nitrogen as we know has nothing to do with the respiration when air comes in it is saturated by nitrogen by 79 percent and when it goes out that is exhaled air also have 79 percent saturation. The water vapors these are variable initially when they enter inside the lungs that is in inhaled air they are variable, but when they go out the air is saturated with the water vapors because we know that the whole all the surfaces which are present inside the respiratory tract they are almost. So, when air goes out it is saturated with water vapors. So, this was all about respiration respiration in plants in animals differences between cellular and organismic respiration and then a detail about the human respiratory system.