3. Why Mammals are Find in Different Size?
The amount of organic phosphates (like DPG) existing in hemoglobin of blood is determining factor of mammal’s bulk
Here I propose a solution to the preceding two questions.
I use an analogy. Let us consider a village with its in habitants. There is an apple garden near it. A person should feed the inhabitants from this garden. This person has only one tray picks up the apples and puts them in the tray, and then he goes to the village. On the way, some of the apples slip from the tray. Because the village is near, he could carry some of them to the village. But if the village was far away, all the apples would slip from the tray and the inhabitants would die without apples. So this person should find a way to carry the apples for a long distance. We compare this example with the mammals’ body.
The villages are like the body’s tissues, the in habitants are the cells, the garden is the lungs, the apples are the oxygen molecules, and the way is the blood ves- sel. That person is the blood and the tray is the red cells. Here, the thing that causes the oxygen molecules stick on the red cells is our point. Now we study how oxygen molecules stick on the red cell. There is hemoglobin in red cells. The oxygen molecules are joined with the hemoglobin and this causes that the oxygen molecules stick to the red cells. With little consider- ations, we find that the oxygen molecules do not stick to the red cells with a similar strength in the body of all the mammals. This stickiness is much stronger in some species and is weaker in some other. This stickiness is related to the size of the mammal. The more this stickiness, the more the oxygen molecules can be carried in the blood. This will cause the body to be larger. On the contrary, if the stickiness is weaker, the oxygen molecules would move less in the blood and so the body has to be small.
Look at the following information:
The mammal species and the oxygen pressure in which the red cell’s hemoglobin sends most of it’s oxygen to the tissues.
Mouse ....................45 mmHg
Rat .........................42 mmHg
Cat ........................38 mmHg
Fox ........................35 mmHg
Sheep ....................30 mmHg
Horse ....................25 mmHg
Elephant ................22.5 mmHg
The oxygen molecules enter into the blood from lungs and stick to the red cells. After moving a distance they reach the tissues and get separated from the red cells and then the cell use them. What the oxygen molecules mix with hemoglobin and stick to the red cell? What causes the oxygen molecules be separated from the hemoglobin in the tissues? And the most important is that, what causes the oxygen molecules be separated from the red cells soon or late?
The transfer of oxygen to the blood is done by circulation. So the reason is the oxygen’s thickness or pressure. The oxygen’s pressure in lungs is more than the lung’s capillaries. So the oxygen enters into the blood from the lungs. these oxy- gen molecules mix with the hemoglobin in the red cells, then move to the heart and after it, move to the tissues. When these molecules reach near the tissues, they get separated from the red cells because of the lowness of oxygen pressure. But this sep- aration is different among the mammals’ species. As it is shown in the table above, most of the oxygen molecules get separated from the red cell’s hemoglobin in mouse’s body in 45 mmHg. But this happens in 22.5 mmHg in elephant’s body. It means that the oxygen molecules mix with hemoglobin very weakly in mouse’s body. Getting a little far from the lungs the oxy- gen’s thickness gets weaker and so they get separated from the hemoglobin and so the red cells can not move for longer distances.
But in elephant’s body have stronger stickiness; the oxygen’s pressure gets lower by getting far from the lungs. But most of oxygen molecules still stick to the hemoglobin’s and move to the far tissues. On the other hand, the mouse’s tissues can not be far from the lungs and heart because the oxygen can move a long distance but it is different in whale and elephant’s body because they are sure that all their tissues will get oxygen. Now we have question, why do we have this difference in stickiness among the mammals? To say it simply, why the mixture of oxygen molecules with hemoglobin is stronger in elephant’s blood than the mouse?
The answer to this question relates to the organic phosphate like (DPG) which exists in mammal’s blood. The more organic phosphate the less the stickiness be- tween oxygen and hemoglobin, like the hemoglobin of mouse. On the contrary, the less these organic phosphate the more the stickiness power, like the elephants body.
Simply, organic phosphates make the stickiness between the oxygen molecules and hemoglobin weaker so there is an op- posite relation between the amount of organic phosphate and the stickiness power. The less the amount of organic phosphates, the larger the size of mammals.
Another question may be discussed at this stage. Let us continue using again an analogy. A rich man can buy a spacious house: more the power of his wealth, more spacious his house, according the same ratio. But what is the limit? If sameone has a lot of money, can he buy a house as large as a city? What is the space of the most spa- cious house he is able to buy? What are the factors restricting the final limit of space of the house? We found out that if an animal has a more power of its blood circulatory system, it is possible to have a larger bulk. But up to what limits? If an animals’ blood circulatory system is so strong to be able to overcome the gravity, is it possible to have a bulk size as great as a mountain? What is the decisive factor limiting the final size of animals?Answer to this question forms one of the other chapters of my book.