Final answer:
The 'crude/heavy membrane fraction P2' is a part of a subcellular fractionation process used in cell biology to isolate cellular components, and it includes organelles like mitochondria and synaptosomes that are heavier than the cytosol but lighter than the nucleus.
Step-by-step explanation:
When a student asks about the 'crude/heavy membrane fraction P2' in the context of synaptosome isolation using subcellular fractionation, they are referring to a step in the process of separating cellular components. The P2 fraction typically contains cell organelles like mitochondria, lysosomes, and synaptosomes that are heavier than the soluble cytosolic components (S1 fraction) but lighter than the nuclear and debris fraction (P1). This fraction is obtained after centrifugation of the homogenate, via differential centrifugation, which allows for the separation of particles based on mass.
Subcellular fractionation techniques can involve differential centrifugation, density-gradient centrifugation, or even more advanced methods like free-flow electrophoresis (FFE), immunoaffinity purification, and fluorescent-assisted organelle sorting (FAOS). Each method has its own set of advantages for isolating specific organelles or proteins from complex mixtures, and the P2 fraction is just one of the potential fractions obtained during the differentiation process.