DNA replication

[kapital]

When DNA is replicating, how can the polymerase add so many bases so fast? Where does she get them?

[Mr Skeptic]

The bases are just floating around in solution, and occasionally collide with the polymerase. At the small scales, molecules move much faster than you might think.

[CharonY]

The nucleotides hang around. Not the pure bases. Also remember that the volume is rather low.

[Mr Skeptic]

Well, I could have called them deoxyribonucleotide triphosphates but didn't feel like it. Incidentally, two of the phosphates are removed to provide energy, just like ATP. Edit: As CharonY said, it's like but not the same as ATP, I forgot about the extra deoxy bit.

Edited October 7, 2009 by Mr Skeptic
oops

[CharonY]

Not quite, for DNA synthesis deoxy-ATP (and the respective other nucleotides) is used. Also ATP-dependent energy transfer is normally limited to a single phosphate residue (i.e. from ATP to ADP). Whereas during DNA polymerization PPi is removed. But yes, the principle is very similar.

Edited October 7, 2009 by CharonY

[kapital]

Ok. Is the transport from cytoplasma to nucleus work of enyzmes? Is the transport of nucleotides to cell connected with the needs of cells?

[CharonY]

The nucleus possesses porins (essentially proteins that form a channel) that are large enough to let nucleotides pass. IIRC there was no difference in nucleotide concentration between between nucleus and cytoplasma, further indicating free diffusion.