Explanation of Cell Specialization | Sciencing
Thread: cell differentiation and cell specialisation "Can i find the area between your curves? Maybe i can lay tangent to your derivative and. Cell specialization, also known as cell differentiation, is the process by which generic cells change into specific cells meant to do certain tasks. Learn about and revise mitosis and cell specialisation with BBC Bitesize for GCSE Combined Science, OCR Cell differentiation Spongy mesophyll, Allow gases to circulate for the exchange of gases between the leaf and the environment.
Recall that inside the nucleus of each cell is your DNA. This is our library, this is our set of genetic instructions for building our entire body. Genes give our cells specific instructions on how to make different kinds of proteins. Having different proteins around, that changes the way our cells look and it changes the way our cells act so it gives our cells really different abilities.
What I mean with the exception of the red blood cells which lack nucleii, every single somatic cell in your body contains the exact same DNA. Yet this muscle cell here, right, it looks and it acts differently to this neuron here.
That's because they're each reading different books in our DNA library. They're using different genes to make their proteins. Just a bit of terminology here, when a cell is actively using certain genes, it's said to be expressing those genes. A gene being expressed is said to be turned on, and one not being expressed is turned off, so just keep that in mind.
Why am I telling you all of this? Because in the end it all relates to how our stem cells all the way up here end up differentiating into our specialized cells down here.
The bottom line is in order to differentiate to, for example, specialize into our muscle cell here, this stem cell up here turned on its muscle cell genes. Here's its DNA and I'm highlighting its muscle cell genes that it turned on right now.
It also turned off some other genes. By turning on its muscle cell genes, now proteins get made within the cell that changes how the cell looks. See now it's a bit elongated, right, this muscle cell here. It also changes its functions. Now our muscle cell has contractile proteins in it to help it be a nice useful muscle cell to help us move around, right?
Now our neuron here, our stem cell turned on its become-a-neuron genes here, right? It turned off some other ones, and then the cell started producing all the proteins it needed to turn into a neuron. Like the proteins that would make it elongate like this and grow out these little spiky things up here called dendrites, okay? Let me also say that remember our stem cell up here was pluripotent.
Cellular specialization (differentiation) (video) | Khan Academy
It could turn into any of our somatic adult body cells. But once it's specialized into these mature cell types, these can't go on to differentiate into other cells.
They actually can't de-differentiate either. They can't go backwards up to stem cells naturally, at least in us humans. So these cells stick around to form our bodies.
By now you must be wondering what determines what genes in the given cell are turned on or off? In other words, how the heck does this cell know it's time to specialize into a different cell type?
It turns out that cells decide what they're going to grow up to be based on cues they get. These cues can be from their internal environment or their cues can come from their external environment, their outside environment.
Let me just show you two major ways this can happen here, these cues. In the development of lots of different organisms, us humans included, we start out with one cell, right, the zygote.
Our zygote has these little proteins called transcription factors floating around in its cytoplasm. Also the precursors of these transcription factors are there too, little bits of MRNA. Multicellular specialization at the cellular level is possible because the environment faced by a cell in a multicellular organism is quite different from and more benign than that faced by a single-cell organism in its natural environment.
Cellular specialization (differentiation)
Metazoan cells live in a cooperative, nearly homeostatic environment protected and nourished by the whole organism. In contrast, a single-cell organism must be prepared to deal with all sorts of unfavorable circumstances such as predators, changing abundance of nutrients, and toxic chemicals.
That flexibility requires each cell to support a large complex repertoire of behavior. For individual cells, one obvious cost is energy consumption; the maintenance of all the unnecessary cellular machinery is not free.
Since each specialized Metazoan cell uses only a small fraction of the total genome, its energy costs can be dramatically reduced.
But also cell specialization induces very different and incompatible cellular biochemistry, shape, and function. A nerve cell could not function as a reliable communication channel between point A and point B if it also builds bone around itself, fills itself with hemoglobin to carry oxygen, accumulates fat, and secretes stomach acid.
Perhaps the most important benefit is that specialization reduces the number and type of messages to which the cell can respond. There are thousands of different types of molecular messages active in a complex multicellular organism. Each cell responds to just a small subset.
Specialization and Differentiation
It would be worse than meaningless for a cell to retain the ability to respond to all these messages — it would be chaos. A cell that had receptors for all molecular messages would be susceptible to all viruses. Viruses infect a cell by binding to particular surface proteins.
Since different surface proteins characterize different specialized cells, each kind of virus can infect only certain types of cells -- those that have the right binding sites. The cold virus infects cells in the nasal passages, the hepatitis virus infects certain liver cells, the HIV virus infects certain cells in the immune system, and so forth.Cellular specialization (differentiation) - Cells - MCAT - Khan Academy
If every cell expressed all cell markers, any virus could bind to and infect all cells.