cell organelles are separated by centrifugation at 0-4 C temp.At this temp.how organelles remain unfrozen?

Answer 1

We have used the pH-dependent fluorochrome fluorescein-dextran (FD) to study the acidification of prelysosomal vacuoles (endosomes) and lysosomes isolated from cultured macrophages and fibroblasts. FD was internalized by pinocytosis under conditions that allowed its selective localization in endosomes (1- to 5-min pulse) or in lysosomes (5-min pulse, 30-min chase). Fibroblasts were also exposed to FD at 20 degrees C, at which temperature endosome-lysosome fusion is inhibited. Cells were homogenized and labeled organelles were separated by centrifugation in Percoll density gradients. The addition of ATP rapidly decreased the internal pH of both endosomes and lysosomes, as indicated by a decrease in fluorescence intensity. The pH gradient was dissipated by H+ ionophores and ammonium chloride. Acidification was not affected by inhibitors of the mitochondrial F1,F0-ATPase or the Na+, K, K+-ATPase and did not require permeant anions, Na+, or K+. Of the inhibitors tested, only N-ethylmaleimide prevented the ATP-dependent acidification of both compartments. These findings provide direct support for the existence of an acidic prelysosomal compartment that may be acidified via the same type of H+ pump believed to operate in lysosomes and secretory granules.

Answer 2

The cytoplasm contained within most organelles is a complex solution of water (that would freeze at these temperatures), and polysaccharides, proteins, lipids and a whole host of other molecules. These molecules will lower the freezing point of the solution to lower than -4 C. I am not sure of the exact freezing point of cytoplasm but when I worked in the lab if we put cells in to the -20 C freezers they did freeze, so it must be between -4 and -20 somewhere.

Answer 3

The freezing temp of PURE WATER is 0 degrees C. This means EVERYTHING else iis SOMETHING OTHER than 0 degrees (something above 0). Organelles have other elements in them, changing the molecular structure of the molecule, causing this.

Answer 4

Mitochondria at the instantaneous are organelles, yet their structure exhibits they began their evolutionary experience as separate cells, and someway advanced into the organelle we see at present. the significant reason behind this concept is that mitochondria (and chloroplasts) have their own genomes, and those genomes are very comparable to bacterial genomes.