Bio-Pac 03: Objective 01-03 and 05 Flashcards
Objective 1. Describe the structure of the plasma membrane.
The plasma membrane’s structure is made up of a bilayer of lipids with protein molecules embedded within the bilayer. These bilayers are made up of phospholipids. A phospholipid has instead of a third fatty acid a phosphate group attached to a small organic section. The head of the phosphate is polar meaning that it is soluble in water, and the fatty acids (the other end) are nonpolar meaning that they are not soluble in water, because of this the head or phosphate group is on the outside and the fatty acids are on the inside. Phospholipids are not bonded together but stay together because of polarity, and because of this the phospholipids in the cell membrane can move sideways—fluid mosaic model description. The phospholipids make up the cell membrane and between some of these phospholipids/within the cell membrane, there are proteins embedded within the plasma membrane, and there is also cholesterol within the cell membrane to strengthen the cell membrane.
Objective 2. Differentiate between a triglyceride, a lipid, and a phospholipid.
A triglyceride lipid has three fatty acids attached to a glycerol molecule, a lipid has two fatty acids attached to a glycerol molecule, and a phospholipid has two fatty acids attached to the glycerol molecule and instead of having a third fatty acid there is a phosphate group instead. This phosphate group has makes the head polar, water soluble, while the fatty acids and glycerol molecule is nonpolar, non-water soluble.
Objective 3. Describe the plasma membrane in terms of the fluid mosaic model.
Fluid mosaic means that similar molecules are free to move sideways within the membrane of a cell. The plasma membrane is considered fluid mosaic because the phospholipids are not chemically bonded to stay together because then the membrane would not be able to move meaning that they could not create different sized pore holes to be selectively permeable. Because the cell membrane needs to be selectively permeable the phospholipids are bonded together in the bilayer by polarity, and this keeps the phospholipids from floating away but also to allow them to change shape. The allowing of similar lipids to move sideways within the membrane of the cell is called the fluid mosaic model description.
Objective 5. Describe the function of the membrane proteins and membrane cholesterol.
The proteins that are embedded in the bilayer of phospholipids that are bonded by polarity and the cholesterol in the cell membrane both have functions. The placement of the proteins is to determine which particles may pass across the membrane. They also serve as markers so your own immune system can tell what is a part of your body, and not a part of your body—foreign body—threat to your—example: bacterium. The protein then when it finds a foreign body such as a bacterium will send a signal so white blood cells know that you need to come to attack the foreign body. The other function is to determine which molecules can move in and out of the cell. The function of cholesterol is to strengthen the fluid mosaic of the cell, but if you don’t have enough cholesterol it is not good because the cell’s membrane is too fluid, and if you have too much cholesterol it is also not good because the cell’s membrane becomes too stiff (you can’t change the pore cell size easily meaning that you can’t let some things out or into the cell. Another function is to keep the fatty acid tails from sticking together.
