The RBCs in our body perform a vital role of oxygen transporration. But they do not possess nucleus,mitochondria to co ordinate any cellular activities. But it lives for 120 days. How does it get energy? Does it perform anaerobic respiration?
A red blood cell is made up of red pigments, known as as hemoglobins. Each hemoglobin is made up of 4 iron, known as hemes, and proteins, known as globins.The 4 hemes are each attach to 1 globin, forming what is known as a polypeptide chain, a chain of amino acids held together by peptide bonds. This structure helps the red blood cell to carry more oxygen than it otherwise could. This complementary to the cell's structure. There are two important points about the structure of the RBC. For one, as previously stated, it has no nucleus. This gives the cell more space to hold more oxygen. Also, the lack of nucleus reduces the weight of the cell greatly, allowing the cell to be much faster in motion. RBC's die after an average of 120 days. After that, they are transported to the liver, where they are broken down and used to build new cells. Millions of cells are created every second through the bone marrow.
The red blood cell does not have mitochondria and other organelles that may otherwise be present in a normal cell. Mitochondria's main purpose is to create energy through the respiration, which requires oxygen. Since the RBC doesn't do much other than transport oxygen, it wouldn't be suitable for it to have a mitochondria, espesically since the RBC would waste much more oxygen. Therefore, RBC depend on anaerobic respiration, instead of aerobic respiration. In anaerobic respiration, oxygen is not needed and would be much suitable for red blood cells.
In humans (and all mammals), red blood cells lack mitochondria and therefore has no functional TCA cycle. They metabolize glucose mainly via glycolysis, forming lactate which is released from the cells; this yields 2 ATP for each glucose molecule, much less than complete oxidation (ca 30 ATP), but enough to support the red blood cells' energy needs.
There is some oxidation of glucose to CO2 in red blood cells though. This occurs mainly in the pentose phosphate pathway or "shunt", where 1 carbon of glucose is released as CO2, and the energy extracted is used to reduce NADP to NADPH, which functions as an antioxidant. The resulting 5-carbon sugars (pentoses) are then rearranged to a 3-carbon sugar (glyceraldehyde phosphate) which enter glycolysis again. Hence the term "shunt": 5/6 of the glucose carbon that enter actually comes back to glycolysis again.
By varying flux through the PPP, cells can balance the use of glucose for ATP (energy) or NADPH (antioxidant). Studies estimate that in human red blood cells, 10--30% of hexokinase flux is diverted through the PPP, and the remainder through upper glycolysis (see this and this article). This corresponds to 2--5% of glucose carbon released as CO2, and the remainder metabolized to lactate.
Note that the above apply to mammalian red blood cells. Red cells of other vertebrates, including birds and fish, retain both their nucleus and mitochondria, and their metabolism is different.
A red blood cell is made up of red pigments, known as as hemoglobins. Each hemoglobin is made up of 4 iron, known as hemes, and proteins, known as globins.The 4 hemes are each attach to 1 globin, forming what is known as a polypeptide chain, a chain of amino acids held together by peptide bonds. This structure helps the red blood cell to carry more oxygen than it otherwise could. This complementary to the cell's structure. There are two important points about the structure of the RBC. For one, as previously stated, it has no nucleus. This gives the cell more space to hold more oxygen. Also, the lack of nucleus reduces the weight of the cell greatly, allowing the cell to be much faster in motion. RBC's die after an average of 120 days. After that, they are transported to the liver, where they are broken down and used to build new cells. Millions of cells are created every second through the bone marrow.
The red blood cell does not have mitochondria and other organelles that may otherwise be present in a normal cell. Mitochondria's main purpose is to create energy through the respiration, which requires oxygen. Since the RBC doesn't do much other than transport oxygen, it wouldn't be suitable for it to have a mitochondria, espesically since the RBC would waste much more oxygen. Therefore, RBC depend on anaerobic respiration, instead of aerobic respiration. In anaerobic respiration, oxygen is not needed and would be much suitable for red blood cells.
In humans (and all mammals), red blood cells lack mitochondria and therefore has no functional TCA cycle. They metabolize glucose mainly via glycolysis, forming lactate which is released from the cells; this yields 2 ATP for each glucose molecule, much less than complete oxidation (ca 30 ATP), but enough to support the red blood cells' energy needs.
There is some oxidation of glucose to CO2 in red blood cells though. This occurs mainly in the pentose phosphate pathway or "shunt", where 1 carbon of glucose is released as CO2, and the energy extracted is used to reduce NADP to NADPH, which functions as an antioxidant. The resulting 5-carbon sugars (pentoses) are then rearranged to a 3-carbon sugar (glyceraldehyde phosphate) which enter glycolysis again. Hence the term "shunt": 5/6 of the glucose carbon that enter actually comes back to glycolysis again.
By varying flux through the PPP, cells can balance the use of glucose for ATP (energy) or NADPH (antioxidant). Studies estimate that in human red blood cells, 10--30% of hexokinase flux is diverted through the PPP, and the remainder through upper glycolysis (see this and this article). This corresponds to 2--5% of glucose carbon released as CO2, and the remainder metabolized to lactate.
Note that the above apply to mammalian red blood cells. Red cells of other vertebrates, including birds and fish, retain both their nucleus and mitochondria, and their metabolism is different.
