drjimbob

Hi, the 2,000 dalton refers to a molecular weight cut off point. The beads used in gel filtration have certain sized pores which allow molecules to either pass through them or not. In this case the maximum size of the molecule that can pass though the pores will have a molecular weight of ~ 2,000. Hope this helps

There is a marked difference between the biosynthesis of haem and chlorophylls. The haem pathway in mammals starts at ALA synthase which catalyses the synthesis of ALA, as the name suggests, and requires succinyl-coA as a cofactor. The plant pathway goes via the C5 pathway to synthesise ALA. This involves three enzyme catalysed steps with glutamate-tRNA cofactor. Plants do synthesise haem, however it is utilised ina different way in comparison to the way in which it is used in mammals. The pathways diversify for haem and chlorophyll at metal ion insertion step - either iron (haem) or magnesium (chlorophyll).n Additionally the subcellular compartmentalisation is markedly different for the porphyrins. If you want any further information please contact me as I studied the pathways as part of my PhD. Hwoever that was a while ago. Hope this helps