Cell Membrane and Transport Material
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Prokaryotic cellsExtremely small.Have a simple internal structure with no membrane-bound organelle. No membrane-bound nucleus.E.g bacteria.Eukaryotic cellsHave a complex internal structure.Many membrane-bound organelles.Membrane-bound nucleus.Plasma membraneThe plasma membrane is the boundary between the inside and outside environment of the cell.Ultra thin and pliable (can bend).Too thin to see with a light microscope because it has a thickness of 0.001mm.Made of phospholipid bilayer ( a double layer of phospholipid molecules.Phospholipids are from the lipid family.Plasma is also called the fluid mosaic model. Because it can pass those liquids and everything through. the proteins embedded in here in the channels allow substances to pass through.Antigens (research what antigens are) are protein which combine with the carbohydrates.The plasma membrane is partially permeable (allows some substances through and others now.DiffusionIn terms of biology, it is the overall movement of particles from a high concentration to a low concentration.For diffusion to occur, there needs to be a high concentration outside the cell, which will then move to the inside. If there is high concentration inside the cell, it will move outside.It will stop diffusion when there is the same concentration inside and outside (when it is equal in concentration).Diffusion can occur for gases. E.g If you spray something in a room, the gas particles will diffuse to take up all the available space it can.Hydrophilic: substances that readily dissolve in water (water loving)Lipophilic: substances that have low water solubility or do not dissolve in water are able to dissolve in or mix with lipids.Lipophilic substances can cross the plasma membrane readily.E.g alcoholThe difference in concentration provides a concentration gradient.The steeper the gradient, the faster the rate of diffusion- until the equilibrium is reached.Does not require energy because it’s just a net movement.Size mattersSmall molecules (oxygen, water, carbon dioxide) can pass through the cell membrane by diffusion. This is because we need all three of these things readily.Bigger ones can pass by protein channels.Channel mediated: substances that are unable to carry out simple diffusion, cross the membrane with the assistance of protein channels. Does not need energy for this.

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High Concentration And Cell Membrane. (June 14, 2021). Retrieved from https://www.freeessays.education/high-concentration-and-cell-membrane-essay/