Excuse me, why do mature human red blood cells survive longer than ordinary non nucleated cells? Tha

Okay, so it's about cell differentiation, apoptosis, and protein function. When the red blood cell is not fully differentiated, its nucleus disappears first, as you said, part of the mRNA remains, and the ribosomes do not disappear because the differentiation does not end, and then the mRNA carrying the genetic information is translated into proteins, making the cell a red blood cell with multiple functions. The human body cannot do without red blood cells, so the reason for natural selection is that red blood cells must be more viable than those simple non-nucleated cells.

And red blood cells can get glucose by assisting in diffusion.

I looked up that ribosomes are indeed organelles. mRNA can leave the ribosome and "work independently", for example, to synthesize cDNA. This requires reverse transcriptase.

Eukaryotes are slightly different from prokaryotes but both are made up of two subunits, large and small. It is composed of RNA bound to proteins.

mRNA is formed by splicing, processing, and maturation of hnRNA (nuclear heterogeneous RNA) (this process is supposed to occur when red blood cells are immature). He is a template for protein translation, through which metatRNAs transport amino acids to synthesize proteins. In this translation process, only ATP, starting complex, EIF termination factor are required.

The protein synthesized should be related to hemoglobin.

When red blood cells mature, the nucleus breaks down and disappears, leaving only hemoglobin in the cell to facilitate the transport of oxygen.

However, I feel that the reason why red blood cells survive longer has nothing to do with mRNA. It is a functional problem with red blood cells.

Problem 1: Synthesis of proteins to provide vital energy (only a very small amount).

Supplement 1: Ribosomes are present in immature red blood cells, so they are translated in immature red blood cells.

Supplement 2: No. (because mature red blood cells have no transcription primordial material to form proteins except for a small amount of DNA and RNA in the cytoplasm, so they cannot form proteins).

Ribosomes are no longer needed after mRNA is generated. mRNA can be translated into proteins outside the nucleus. What is needed for this process is ribosome.

High School Biology Compulsory 2: M RNA is messenger RNA A small amount of M RNA molecules can quickly synthesize a large number of proteins.

Red blood cells have no nucleus and no organelles, and their main function is to transport and exchange oxygen and carbon dioxide. The function of each cell is genetically determined and the result of long-term evolution, and this is the case with red blood cells, which have a nucleus at the beginning and are not the result of gene selective expression cell differentiation after maturation.

Red blood cells, also known as red blood cells, are often abbreviated as RBC in English in routine laboratory tests, and are the most abundant blood cells in the blood, and they are also the most important medium for transporting oxygen through the blood in vertebrates, and also have immune functions. Mammalian mature red blood cells are nucleated, which means they have lost their DNA. Red blood cells also do not have mitochondria, they release energy by breaking down glucose.

In addition to being nucleated, human mature red blood cells also have cytoplasm, hemoglobin, platelets, and no organelles.

This morphology of human mature red blood cells gives it a large surface area, which facilitates full gas exchange with the surrounding plasma, so as to maximize oxygen transport, and the structural characteristics of red blood cells can reduce their own metabolic rate.

Due to the lack of various organelles in the mature red blood cells of the human body, there are no other biological membranes except the cell membrane, such as the mitochondrial membrane, the endoplasmic reticulum membrane and the Golgi membrane. Because of this, blood cells are often used as experimental materials in blood shadow experiments.

Not all living erythrocytes do not have a nucleus of cells, but human and mammalian mature erythrocytes are nucleated and have no organelles, only cell membranes and cytoplasm other than organelles, while the erythrocytes of birds and amphibians are nucleated and have the same structure as normal cells.

Human red blood cells are like a biconcave round cake, thick on the periphery and thin in the middle, with an average diameter of about 7um, a thickness of 2um around the periphery, and a thickness of 1um in the middle. Red blood cells are characterized by the presence of iron-containing hemoglobin. Hemoglobin binds to oxygen and makes up one-third of the total body weight of cells.

Another important substance in red blood cells is carbonic anhydrase, which helps in the transport of carbon dioxide. The main function of red blood cells is to transport oxygen and carbon dioxide. Its shape and size favor the rapid passage of oxygen and carbon dioxide throughout the cell.

The number of red blood cells in adult men in China is 4.5 million to 5.5 million per cubic millimeter of blood, with an average of 5 million; The number of red blood cells per cubic millimeter of blood in an adult woman ranges from 3.8 million to 4.6 million, with an average of 4.2 million. There is no gender difference in the number of red blood cells between infants and children.

After red blood cells are produced in the red bone marrow, in the initial stages, they have a nucleus. As the cell develops, the nucleus gradually disappears during the maturation stage. Neither a cytoplasm nor a nucleus without a cytoplasm can live alone.

Therefore, red blood cells without a nucleus should cease physiological activity.

However, this is not the case. In the initial stage of cell development, the RNA synthesized in the nucleus is transported into the cytoplasm through the nuclear pore, directing and controlling the synthesis of proteins, and controlling the development of the cell.

When the nucleus disappears, these RNAs can remain in the cytoplasm for a period of time, continuing to direct and control protein synthesis, a role known as nucleus retency. It is this effect that allows the nucleated red blood cells to last for a period of time. Normal vital activity, this is the main reason why nucleated red blood cells are able to live.

However, as RNA is degraded and disappears in the cytoplasm, protein synthesis also ends. Protein is indispensable for cellular vital activities, and the vital activities of red blood cells cease due to the decrease in proteins. Of course, in the cytoplasm of red blood cells, there are still a certain number of cytoplasmic genes, but they are insignificant compared to nuclear genes and are not enough to maintain the normal physiological activities of red blood cells.

The role of red blood cells is only to rely on hemoglobin to transport oxygen, and does not assume the responsibility of transmitting genetic material, so the result of long-term evolution is that the nucleus and organelles disappear when they mature, and its essence is the selective expression of genes.

The function of red blood cells is to transport oxygen, and if there is a nucleus, red blood cells also consume oxygen, so the transport capacity is reduced...

Cells differentiate in a favorable direction and perform certain functions, so that the division of labor is close, and the cells are interconnected.

Red blood cells contain hemoglobin, which transports oxygen, and in order to make room for a large amount of oxygen, there is no nucleus and other organelles.

Not only humans, but also other mammals.

First, consider from the perspective of structure and function.

There is no nucleus in order to have a more powerful ability to transport oxygen to meet the energy needs of mammals (generally speaking, mammals have a large range of activities and high mobility, and homeothermic animals consume more energy).

Second: from an evolutionary point of view.

Seedlessness evolved slowly.

Third: mammals vs birds.

In general, mammals are more complex, long-lived, and larger, requiring tools to transport oxygen more efficiently.

In humans and other mammals, mature mammalian erythrocytes are nucleated and biconcave disc-shaped, which increases their surface area and makes it easier for substances to pass through their cell membranes and facilitate gas transport.

It can also be said that red blood cells do not have a nucleus, but are degenerate, because the nucleus is a burden to its functional duties.

The main function of mature red blood cells in the body is to transport oxygen.

In order to make room to carry as many oxygen-carrying molecules as possible, the nucleus gradually degenerates.

This is the result of tens of millions of years of human evolution to survive in order to better adapt to the environment, too"Survival of the fittest, survival of the fittest"The result of natural selection.

The current college entrance examination syllabus does not require this knowledge point. You just need to understand. Don't worry about the exam having such questions.

I'm also thinking about this question, if mammalian red blood cells don't have a nucleus in order to better carry oxygen, then do flying birds have less oxygen-carrying capacity than mammals? Birds have double breathing, but this does not mean that red blood cells with a nucleus are less oxygen-carrying than birds.

It can only be said that in the long period of evolution, mammalian erythrocytes have a predominance without a nucleus, thus eliminating individuals with a nucleus. This kind of elimination I think that the replacement of red blood cells with a nucleus is slow, and the aging red blood cells can survive under the weak expression of the nucleus if they have poor oxygen-carrying capacity, while the red blood cells without a nucleus are replaced faster, so as to better carry oxygen.

The red blood cells of mammals such as humans do not have a nucleus, of course, pigs are no exception, and human and mammalian are formed by bone marrow stem cells through multiple differentiations, including the process of excreting the nucleus, the specific reason is not clear, and perhaps saving space is also an explanation. After our red blood cells are nucleated, they are engulfed by macrophages in our blood after 100-120 days because they cannot metabolize themselves. The composition of our blood is also completely changed once in a certain period.

1.This is the result of the selective expression of genes.

I feel that the absence of a nucleus in mammalian RBCs is a result of evolution :

The reasons for this can be summarized as follows:

1. Without a nucleus, the cell loses a large energy user, saving energy for the rest of the body.

2.Reduced volume, easy to cross the capillaries.

3.By increasing the surface area, it is theoretically calculated that the existing shape of red blood cells is better than that of other shapes for gas exchange, and it is easier to slide through the mold blood vessels than square shapes, and it is not easy to accumulate phenomenon.

4.After the red blood cells mature, the expressed genes are fixed and make them lose their ability to reproduce, reducing the possibility of mutation and protecting the safety and health of the body.

I think it's probably because the main function of mature red blood cells is to transport oxygen and carbon dioxide. It needs to enter the tissue through the capillary gap, and when it passes through the blood vessels, the blood cells need to be dispersed and matched, and it will be a burden to have a nucleus, so it is necessary to remove the nucleus.