Essay About Fluidity Of Membranes And Cellsvesicle Move Materials

Endocytosis – Vesicle Movement in Cells
EndocytosisThe fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosisVesicle is a small sac of membrane with flied inside, they are normally present in eukaryotic cellsDynamic feature of cellsConstructed, moved around and then deconstructedCan be happen because of the fluidity of membranes, which allows structures surrounded by a membrane to change shape and moveThe vesicle is formed on the inside of the plasma membrane, which contains material that was outside of the cellMethod taking materials into the cellContain water and solutes from outside the cell but also often contain larger molecules needed by the cell that cannot pass the plasma membranee.g. Placenta including antibodies are absorbed into the fetus by endocytosise.g. Some types of white blood cells take in pathogens by endocytosis and then kill them, as body’s response to infectionVesicle movement in cellsVesicle move materials within cellsCan be used to move materials around inside ells e.g. in secretory cells, protein is synthesized by ribosomes on rER and accumulates inside of itVesicles containing proteins bud off the eEr and carry them to the Golgi apparatusThe vesicles fuse with Golgi, which make protein into its final form, bud off the Golgi and move to the plasma membrane, where protein is secretedIn a growing cell, the area of the plasma membrane needs to increasePhospholipids ae synthesized and become inserted into the rER membraneThis method can also used to increase the size of organellesExocytosisThe fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosisvesicles fuses with the plasma membrane, the contents are then outside of the membrane and therefore outside of the cellpolypeptides in the enzymes are synthesized by eER, processed in Golgi then carried to the membrane in vesicles for exocytosisAlso be used to expel waste productse.g. removal of excess water from unicellular organismsWater is loaded into a vesicle, sometimes called a contractile vacuole, then moved to the plasma membrane for expulsion by exocytosisCan be easily seen in paramecium, by using microscopeSimple diffusionParticles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.spreading particlesParticles move from higher concentration to an area of lower concentrationNo need energy it is a passive processInvolves particles passing between the phospholipids in the membraneCan only happen if the phospholipid bilayer is permeable to the particlesNon-polar oxygen diffuse easilyThe center of membrane is hydrophobic, ions with positive or negative charges cannot easily pass throughPolar molecules over their surface can diffuse at low rates between the phospholipids of the membraneSmall polar particles (e.g. ethanol gas/urea) pass through more easilyFacilitated diffusionParticles move across membranes by simple diffusion, facilitated diffusion, osmosis and active  transport.