How does a white blood cell know where to go and what to attack? How does a RNA know that it has to deliver a message to a ribosome? How do antibodies know what to attack? How does a virus know where to go? etc...
How can it do all these things without a brain or something?
I'm very curious!
2007-10-01 06:39:05 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Biology
Just explain how...
2007-10-01 06:44:34 · update #1
Life is the result of macromolecules changing shape. Shape determines the reactions that the molecule is competent to catalyze or regulate. These are dumb molecules without intelligence. They know nothing. They are responding to the local chemical concentration of molecules that interact with each other.
White blood cells don't know that it's chasing down a bacterium. It has receptors molecules on the cell membrane that are capable of detecting other molecules, including those found on bacteria. When the receptors meet bacterial macromolecules, the shape of the receptor changes. It brings together other molecules inside the cell that initiate other chemical reactions (phosphorlyation of tyrosine) that then is capable of interacting with new molecules because shape has changed.
The WBC "knows" the direction of the bacteria because more receptors are going to be activated in the direction of the bacteria. Both activating and inhibitory signals inside the cell causes cytoskeletal changes by initiating polymerization in the direction of greatest activation and blocks polymerization elsewhere. This system of macromolecules interacting causes movement in the direction of the bacteria.
RNA made in the nucleus is bound by RNA binding proteins. Some of these proteins are export factors that initiate movement out of the nucleus. The export factors recognizes RNA of particular shape (tRNAs, pre-miRNAs) or the proteins that bind to mRNA after splicing (exon junction complex, phosphorylated SR proteins). The export factors have a shape that changes when bound to the cargo and it interacts with the proteins in the nuclear pore complex in the membrane to move the mRNA in one direction out of the nucleus. In the cytosol, 5'cap binding protein fits the shape of the 5'cap mRNA, other proteins recognizes the poly-A binding proteins. The joining of these proteins then is capable of interacting with the small ribosomal subunit. The small ribosomal subunit then scans the mRNA until it recognizes a particular shape, the Kozak sequence and the AUG start codon. Some viruses have an RNA that is capable of attracting ribosomes even without a 5' cap or polyA tail because the structure (shape) of the RNA is similar enough to initiating factors to interact with the ribosome. etc...
Everything is about the right shapes interacting.
2007-10-02 19:32:34 · answer #1 · answered by Nimrod 5 · 0⤊ 0⤋
Most of these are programmed to move towards a specific chemical attractants. White blood cells move towards cellular debris or foreign protein or germs. Sperms move towards the egg by similar chemical attraction (androgamones and gyenogamones). Antibodies are produced by specialized white blood cells that congregate at the site where antigens are produced. The movements towards a chemical stimulus are called taxis.
2007-10-01 15:33:59 · answer #2 · answered by BP-LO 4 · 0⤊ 0⤋
Hi. None of these things "know" anything. They are simply responding in a certain way to external stimuli or chemical signals.
2007-10-01 13:43:22 · answer #3 · answered by Cirric 7 · 1⤊ 0⤋
the 1st question is due to resistance capacity and the 2nd is due to thefunctions of the body organisms. hmmm ........i dont know the rest.... sorry.....
2007-10-01 14:03:30 · answer #4 · answered by poori 2 · 0⤊ 0⤋