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Cell Theory and Membrane - Coggle Diagram
Cell Theory and Membrane
Cell Theory
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Cells contain DNA, the genetic information, which is passed on to daughter cells
Some organisms are unicellular, i.e they are made up of one cell, while others are multicellular and consist of large numbers of cells of different types that have a hierarchical organisational structure
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The Cell Membrane
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Control the movement of materials including nutrients and wastes between the cell and the extracellular environment
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The cell membrane is describes as the fluid mosaic model which states that the membrane is fluid as individual phospholipids move within and between layers, and contain a mosaic of embedded proteins
Lipids
three types: phospholipids, glycolipids and cholesterol
Phospholipids
molecules consisting of a head containing glycerol and a phosphate group, and two tails composed of fatty acids
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Phospholipids form a bilayer when exposed to water. The hydrophobic tails face the interior of the bilayer and the hydrophilic heads face the water on either side of the cell membrane
The hydrophobic interior has characteristics of a fluid as the fatty acid tails are free to move over a short distance. Membrane become more fluid when phospholipids move closer together
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Cholesterol
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restricts the movement of phospholipids and proteins in the lipid bilayer which prevents the membrane from becoming too solid or fluid
sterols like cholesterol increase the rigidity and firmness of membrane at higher temp by binding lipids together and decrease rigidity at low temp by separating phospholipids from one another.
Glycolipids
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The carbohydrate component of a glycolipid extends into the extracellular environment and is called a glycocalyx. Glycocalyx serves a range of function including cell recognition, responding to stimuli, communication and protection from immune cells (protection from auto immune diseases) and pathogens
Membrane Proteins
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Functions of proteins
Transport: Channel proteins and carrier proteins transport hydrophilic materials across the membrane. Carrier proteins transport raw materials into a cell for metabolism and excrete waste materials from a cell
Receptors: Some proteins recognise and bond to signal molecules such as hormones that cause changes in the metabolism inside a target cell.
Enzymes: Enzymes imbedded in the membrane catalyse substrate specific reaction at the surface or within the cell membrane
Channel: Channel proteins facilitate the rapid diffusion of material between the cell and the extracellular space
Cell recognition: Some proteins (glycoproteins) serve as marker that are recognised by membrane proteins on the surface of other cells. Identification protects host cells from attack by immune systems