how does the receptor second messenger system work?
binding of chemicals to external receptors causes them to change shape of the internal portion which causes the release of a molecule that had been bound to them. the released molecule causes changes inside the cell
a layer of glycoproteins secreted by the cell and found covering the external surface of the cell membrane
what make up the hand-rails and steps of the DNA ladder?
RNA polymerase opens up a gene on a chromosome, then adds complementary RNA bases to the exposed banes on the gene. At the end of the gene, the RNA strand detaches, has parts of itself cut out and other parts spliced together and becomes a messenger RNA
What happens in mitosis?
the nuclear membrane breaks down, the sister chromotids are free int eh cytoplasm, microtubules from the centrosomes (which have split and moved to opposite poles of the cell) attach to the sister chromotids an align them int eh center of the cell, the sisters split and each one is pulled to an opposite pole by its microtubule. ONce at the poles, a new nuclear membrane forms around them.