Both prokaryote and eukaryote cells have a cell membrane. The cell membrane has a vital role in the functioning of a cell as it not only keeps all cellular components of the cell within the cell, but it controls what enters and exits the cell. The membrane covers the surface of all living cells which contains most organelles within the cells, enabling the cells to change shape. While the membrane partakes a number of different functions so the cell can survive, it is most responsible for the action of diffusion and osmosis within the cell.
Phospholipids acts a barrier in the cell membrane to determine what goes in and out of the cell. Small, non-polar molecules generally diffuse across the phospholipid bilayer more easily and quickly compared
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Passive transport is identified as simple diffusion; facilitated diffusion; and osmosis, none of which require ATP. The role of diffusion is the movement of molecules going to a net regions of lower concentrations, determined by the properties of the cell; surrounding solution around the cell; and the diffusing cell (3). Diffusion usually ends up without a gradient, causing the substances to end up in the equilibrium of the cell. Simple diffusion is different to facilitated diffusion because facilitated diffusion requires the use of tubular proteins in order for hydrophilic and larger molecules to pass through the membrane, where as simple diffusion is the movement of smaller, and lipid soluble materials are easier and more capable to diffuse without a lot of energy (4). Active transport requires ATP so membrane proteins can pump the molecules through specialised channels against the concentration gradient. Unlike Active transport, which moves the molecule from a low concentration areas to high concentration areas, Passive transport does the opposite. This form of diffusion is the natural random process by which the molecules move along the concentration gradient, moving it from high concentration areas to low concentration areas