Cell membranes - EdexcelWatch
3 Explain how models such as the fluid mosaic model of cell
membranes are interpretations of data used to develop
scientific explanations of the structure and properties of cell
My teacher has managed to really confuse me on this. Can anyone tell me exactly what I need to know on this specification point?
So first you have a cell. In the cell is the cytoplasm, which is surrounded by the membrane. This is the "fluid" part of the fluid mosaic model.
The mosaic part refers to the phospholipids and the intrinsic and extrinsic proteins in the cell membrane. Have you done about phospholipids? I do AQA, so I'm not sure what you need to know.
All that point is asking is if you know about the structure of the cell/plasma membrane (phospholipids, intrinsic/extrinsic proteins) and all that jazz. (I'm so cool)
And then you need to know the different methods molecules use to cross the membrane (active transport, facilitated diffusion...)
I hope that Help??ed.
^^See what I did there? (I need a life)
The Fluid Mosaic model states that the Cell/Plasma Membrane is made of an Phospholipid Bilayer that is made of individual strands of hydrophobic tails and hydrophilic heads that is set in rows. The Cell Membranes has an semi-permeable property that allows diffusion of materials like O2 and CO2 quickly to aid respiration. How ever some molecules like C6-H12-O6, charged ions, and large molecules would have an hard time diffusing through cell membranes so the cell surface has protein receptor to detect useful large molecules and also have Glycolipids and Glycoproteins polymers which acts as receptors which help bind some molecules. Intrinsic proteins like Protein Channels and Carrier proteins aid in the process of 'Facilitated Diffusion' where large molecules can pass through the cell membrane. Facilitated diffusion is an form of Passive transport because it does not use energy. Carrier proteins change shape to allow these molecules to go through. Active transport also uses carrier proteins but uses energy to allow small and large molecules to travel against it's concentration gradient. It uses energy in the form of ATP which hydrolyses to become ADP+ (Pi) (An Phosphate Group).
Cell membranes also do bulk transportation called Endocytosis which involves the cell engulfing the material outside the cell via detection by intrinsic and extrinic cell receptor. An form of Endocytosis is Phycocytosis where some specialized like lymphocytes/White Blood cell engulfs an bacterium and creates an vesicle where it fuses with the membrane of the Lysosome to digest the Microbe. Exocytosis is the opposite. For example, Golgi apparatus create an vesicle which transport material created in the cell to the cell membrane to be expelled.