Cell membrane (20 slides)
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The cell membrane is composed of a phospholipid bilayer with embedded proteins. Phospholipids form the bilayer structure with their hydrophobic tails facing each other and hydrophilic heads facing outwards. Embedded proteins perform important functions like forming channels to transport molecules, acting as receptors, and providing structure. The fluid mosaic model describes the cell membrane as a fluid structure with components able to move freely within it.
Cell membrane (20 slides)
- 3. Note the kinks in the phospholipid tails. Recall this is due to double bonds (unsaturated) and increases fluidity
- 4. Note the cell membrane is a bilayre, due to spontaneous positioning of the polar and non-polar ends of the phospholipids which form it.
- 5. Note structural support of the protein filaments acting like scaffolding – giving the cell a shape Note also the cholesterol studded here and there on either side of the bilayre; it maintains fluidity, preventing the cell from ‘melting’ in heat and from becoming too rigid in the cold
- 6. In the freeze fracture technique cells are flash frozen in liquid nitrogen, dropped from a height, or split with a knife, and gold is evaporated onto their exposed surfaces; with the hope that something interesting might be visualized on the screen of the scanning electron microscope
- 7. How does a SEM work? The SEM is an instrument that produces a largely magnified image by using electrons instead of light to form an image. A beam of electrons is produced at the top of the microscope by an electron gun. The electron beam follows a vertical path through the microscope, which is held within a vacuum. The beam travels through electromagnetic fields and lenses, which focus the beam down toward the sample. Once the beam hits the sample, electrons and X-rays are ejected from the sample. Detectors collect these X-rays, backscattered electrons, and secondary electrons and convert them into a signal that is sent to a screen similar to a television screen. This produces the final image.
- 9. FUNCTIONS OF THE CELL MEMBRANE PROTEINS Some form "channels" through which various substances enter and depart from the cell. Enzymes help speed up chemical reactions. Some proteins, when attached to special chemicals, serve as receptors, setting functions such as hormone synthesis into operation. This attachment launches the beginning of a certain function such as the synthesis of hormone in the cell. The identifiers of the cell are the proteins receiving information regarding whether other cells in the body are foreign invaders. Some proteins assume structural functions; others serve as attachment points for cells to adhere to one another. Other proteins are important in anchoring the cell skeleton.
- 10. Cell-cell recognition is critically important for any kind of organism to function. This job is mainly undertaken by membrane carbohydrates. In order for cells to recognize each other, they bind to molecules found on the cell’s surface, which happen to mostly be carbohydrates. Membrane carbohydrates sometimes bind covalently to lipids, forming what is to be called a glycolipid, while the majority of membrane carbohydrates are covalently bound to proteins, making the two together glycoproteins. Carbohydrate markers found on red blood cells, for example, dictate what blood type you are.
- 12. Net Diffusion to Equilibrium
- 13. Only small and hydrophobic molecules can diffuse through the cell membrane!
- 14. Recap = Facilitated diffusion is when an assisting protein remains in place and “helps” a molecule across by undergoing a change in shape that moves the binding site from one side of the membrane to the other. It is still passive since the molecule is still moving down their concentration gradient.
- 15. Passive transport: Osmosis = the movement of water through a semi-permeable membrane from high to low concentration
- 16. Tonicity
- 17. Tonicity II
- 18. Active Transport Certain molecules need to be kept in the cell at a concentration that is greater than the surrounding environment. This requires the expenditure of energy, usually in the form of ATP http://www.bing.com/videos/watch/video/membrane-potential/15fba088859d7cfdfe3915fba088859d7cfdfe39-1233195565344?cpkey=6cb98a2ebaadbf1c6c6a6cb98a2ebaadbf1c6c6a-1078418866799%7c%7c%7c%7c
- 19. Proton Pump (active) P roton pump. By pumping H+ out of the cell with the hydrolysis of ATP, proton pumps produce an H+ gradient and a charge separation called a membrane potential . These two forms of potential energy can be used to drive active transport of solutes .
- 20. Coupled Channel (active) (Sucrose/Glucose – H+ Symport)
Editor's Notes
- #10: INCOMPARABLE FUNCTIONS OF THE CELL MEMBRANE PROTEINS The different cell membrane proteins (shown in blue in the diagram) have a number of very important functions: Some form "channels" through which various substances enter and depart from the cell. Enzymes help speed up chemical reactions. Some proteins, when attached to special chemicals, serve as receptors, setting functions such as hormone synthesis into operation. This attachment launches the beginning of a certain function such as the synthesis of hormon in the cell. The identifiers of the cell are the proteins receiving information regarding whether other cells in the body are foreign invaders. Some proteins assume structural functions; others serve as attachment points for cells to adhere to one another. Other proteins are important in anchoring the cell skeleton. Every protein and cell in your body, has been created for a particular purpose, equipped with particular attributes, and specially located in the place where its function needs to be performed. In short, man was created-and every detail in your body is proof of that Creation.