Biological complexity: red cell shape mechanics (Introduction)

by David Turell , Tuesday, September 11, 2018, 01:35 (2266 days ago) @ Balance_Maintained

The red cell has no nucleus, is doughnut shaped but the center is filled with a slim area of the cell. The cell has to change shape to twist its way through tiny capillaries. This shape gives the greatest surface area for gas exchange. The cell handles both oxygen and CO2:

https://www.the-scientist.com/the-literature/how-red-blood-cells-get-their-dimples-6468...

"Back in the 1980s, when Fowler started working with red blood cells, it wasn’t clear whether they even contained myosin. She suspected they might, because the protein appeared to play a role in giving other cells their shapes. After painstaking experiments, Fowler finally showed that red blood cells do carry the protein, but exactly how it influenced erythrocytes’ shape remained a mystery. “We didn’t have the tools to do those experiments then,” she says. The myosin filaments in red blood cells are tiny, only around 200 to 450 nanometers long, making them extremely challenging to image. And the first inhibitor of myosin IIA—the specific protein found in red blood cells—wasn’t developed until the early 2000s, so scientists couldn’t see what happened when the protein wasn’t functioning in the cells.

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"When myosin and actin interact and myosin contracts, the cell membrane stiffens, giving the cell a dimple at its center. Inhibiting the motor activity of the protein causes the myosin filaments to expand so they no longer tug on spectrin and actin. That leads to less tension in the membrane and, ultimately, the disappearance of the dimple.

"By expanding and contracting, the myosin filaments likely make it possible for red blood cells to shape-shift as they tumble in the bloodstream’s shear flow and squeeze through microvessels such as capillaries, then pop back into their dimpled form, Fowler says.

"This discovery could also give clues to how myosin works in other types of cells, Vann Bennett, a biochemist at Duke University who was not involved in the new study, tells The Scientist. “Red blood cells are a true experiment of nature,” he says. “They’ve gotten rid of the cell nucleus, mitochondria, and all cytoskeletal proteins.” These simplified cells “have been a powerhouse for generating concepts about how [plasma] membranes are organized in other cell types,” Bennett explains. Understanding the importance of myosin’s contraction in shaping red blood cells, he says, may help in teasing out its functions in other cell types.

"Another recent study supports myosin’s widespread importance in maintaining cell structure: the research showed the protein is critical for axons to grow and shape themselves, suggesting it could be involved in brain plasticity."

Comment: A supreme design well beyond the capacity of a chance evolutionary mechanism. Since the cell does not have a nucleus it must be programmed to feel blood vessel pressure and respond by altering the myosin's actions. This is an example of automaticity such as I believe bacteria are capable of performing.

Tony: And the mechanism to make that happen would have needed to precede the necessity of them, or it would mean death. Darwinism would break down because premature death would prevent this becoming a dominant trait.

The circulatory system in red-blooded animals had to have this type of cell to handle the fine capillaries that are in all muscle tissues and organs, but less in bone. The hemoglobin molecule that fills these cells does two way duty. Delivering oxygen and taking out CO2, exchanging those gases at the lungs in a beautifully designed system. Not by Darwin.