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19

Unlike erythrocytes that have a very rigid shape and almost cannot change their size (hence the size distribution is indicative and can be used for diagnostic purposes in medicine), lymphocytes can change their size in a wider range, this is why you see the numbers 6-9 and 10-15 μm. And they indeed cluster into several different groups: so-called "large ...


11

Theoretically... 93 million bp/cell x 650 daltons/bp x 10^13 cells/body x 1.66 * 10^-27 kg/dalton = 0.001 kg So I would say it's not too much of a difference :P


8

This 1969 Steensland paper seems to suggest that the membranes of halophiles are stabilized by sodium ions and they rapidly denature at lower-salt conditions (2.2 vs. 4.3 M). The protein composition of the membrane was generally acidic, stabilized by all the Na+. As far as what the role of the halophile membrane is in sheltering the cell from the high ...


7

As you point out human beings (and other organisms) have hundreds of retroviruses and many can be seen in the human genome, some of which appear to be the remains of deactivated viruses, others which may be active. Most retroviruses are not pathogenic - they don't cause disease. This is because many retroviruses replicate slowly, budding and secreting ...


6

DAPI (4',6-diamidino-2-phenylindole) preferentially binds AT-rich DNA (although it binds CG-rich DNA, too), which can give chromosomes distinctive banding patterns if they are polytene or in metaphase. In interphase condensed chromosomes, such as the inactive X chromosomes of female mammals (Barr Body), the relatively high concentration of tightly-packed ...


5

In the process of exocytosis materials which are about to be released are transported in small vesicles to the plasma membrane. The plasma membrane fuses with these vesicles and this sets the substances free on the outside of the cell. See the figure (from here): The other possibility for transport vesicles is that they arrive at their target cell and ...


4

I really like this question as it is such a fundamental underpinning of all life on the planet, yet there is such sparsity of actual information on its origins and why evolution encouraged ATP use over anything else. Here I am talking generally since no specific studies exist in ATP vs other candidates. A lot of the below information is taken from an article ...


1

It is generally known that the smaller (or less complex) an organism is, the more "condensed" it's genome is. For example, bacteria (or some eukaryotes) have operons (http://en.wikipedia.org/wiki/Operon) or overlapping genes using different and they don't have introns, which alltogether saves a lot of space. There are many reasons for that. Available space ...


1

Just to extend the answer from @Amory slightly, I think that the terms active and passive transport are best kept for describing transmembrane movement of molecules. In the case of exocytosis the only transmembrane event is when a secreted protein is first inserted (usually cotranslationally) across the endoplasmic reticulum membrane. I'm not aware of any ...


1

Wikipedia is your friend: Exocytosis... is the durable, energy-consuming process by which a cell directs the contents of secretory vesicles out of the cell membrane and into the extracellular space. and Endocytosis is an energy-using process by which cells absorb molecules (such as proteins) by engulfing them. Emphasis mine. Here's a nifty paper ...



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