biology

855 Words2 Pages

Question 1
The model we use to explain how the cell membrane works is called a fluid mosaic model. The Fluid mosaic model was created by S.J Singer and Garth Nicolson in 1972. Between the living machinery of the inner cell and the harsh conditions of the outside world, stands the cells plasma membrane. As crucial as this barrier is, its surprisingly flexible, push it and it will move, poke hard enough and it will break and begin to regroup. We first look at the molecule called phospholipids when thinking about the plasma membrane. Lipids usually have three fatty acid chains, however this molecule has two fatty acid chains. Instead of the third fatty acid chain, a phosphate group is added on. This phosphate group is what makes the phospholipids so special. It is polar and hydrophilic, whereas the rest of the molecule is non-polar and hydrophobic. The hydrophilic heads point outwards as it attracts water molecules, whereas as the hydrophobic tails point inwards due to its mutual attraction and water repulsion. Therefore creating the phospholipid bilayer, which is the basis of all cellular membranes. Throw in some cholesterol and some carbohydrates and you have the basic structure of a plasma membrane. From chemical analysis, we conclude that there are protein in the cell membrane. Using freeze-fracture imaging and scanning electron microscope, we are able to differentiate between the extracellular surface of the membrane and the inside lipid bilayer. Within these lipid molecules, we also find different proteins, which do various things for the cell. For instance, they receive signal from the world outside, and also transport nutrients and waste. So nature composes the membrane with a composition or mosaic of different lipids, carbo...

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...y is generated, that energy being ATP. It is a folded membrane inside a membrane. The mitochondria looks a lot like a bacteria, and thats because scientists think that they became parts of our cells through endosymbiotic theory. In other words, they became parts of the cell, they produce ATP for that cell and then they get a place to live. Evidence supporting this theory being the fact that the mitochondria produces its own DNA through binary fission. The lysosome has sometimes been coined as the suicide sac. Lysosomes has digestive enzymes inside it that is contained within a membrane. A lysosome could go next to a vesicle that has material that we want to break down and those digestive enzymes will go in there and break it down. Lysosomes gets its name from when it pops the digestive enzymes would go throughout the cell and would kill the cell, dissolve the cell.

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