Co-workers: Adelfa Masculino Date Performed: June 29, 2012
Farrah Belle Barredo
The Cell Membrane
The boundary between any cell and its environment is the plasma membrane, composed of a matrix of phospholipid molecules along with a number of different kinds of proteins. Membranes have different properties and a variety of functions, in large part determined by the specific proteins within the membrane. This experiment is designed to determine the stress that various factors, such as osmotic balance, detergents and pH, have on biological membranes. There are three parts in this experiment. The first part is the synthesis of an artificial membrane. In this experiment, the vegetable oil was added with albumin solution and the albumin bubble breaks, but didn’t rupture but when water was added in vegetable oil, the water breaks easily than the albumin and it didn’t mix with the oil. When albumin was added into the vegetable oil, a bubble forms because air is introduced into the system. The bubble formed remained stable due to protein adsorption at the bubble surface. Water bubble on the other hand breaks easily because it is less viscous than albumin. The second part is the determination of osmotic effect in frog’s blood, mammalian blood and plant. The frog and mammalian bloods are subjected to different NaCl concentrations: 0.1%, 0.7% and 0.16 M, while the plant (Rheo discolor) is subjected to 0.3 M glucose. When the frog and mammalian bloods are subjected to 0.1 % NaCl, an influx of water occurs: the cells swell, the integrity of their membranes is disrupted, allowing the escape of their hemoglobin in the process of hemolysis because the solution is hypotonic. When 0.7% NaCl was added to the bloods, there is no net influx or efflux of water because the solution is isotonic. When 0.16 M NaCl was added to the bloods, the cells lose their normal biconcave shape, undergoing collapse, leading to crenation due to the rapid osmotic efflux of water since the solution is hypertonic. The third part of the experiment is the donnan membrane phenomena. The difference in pH inside minus pH outside of solution is the consequence of the Donnan membrane equilibrium, which only supposes that one of the ions in solution cannot diffuse through the membrane. When acid is added to isoelectric gelatin the osmotic pressure rises at first with increasing hydrogen ion concentration, reaches a maximum at pH 3.5, and then falls again with further fall of the pH. The bromophenol is used in this experiment as an indicator of pH change.
Discussion of Results
A.Synthesis of an Artificial Membrane
Vegetable oil + albumin—albumin bubble breaks, but didn’t rupture Vegetable oil + water --- water breaks easily than albumin but didn’t mix with oil
When vegetable oil was added with albumin, the albumin bubble breaks but didn’t rupture. When vegetable oil was added with water, the water breaks easily than albumin and it didn’t mix with the oil. When albumin was added into the vegetable oil, a bubble forms because air is introduced into the system. The bubble formed remained stable due to protein adsorption at the bubble surface. Proteins functioning as foaming agents such as albumin need certain properties like (a) adsorb rapidly at the interface, (b) show rapid conformational change and rearrangements at the interface, and (c) form viscoelastic ﬁlms via intermolecular interactions. Water bubble on the other hand is less viscous and breaks easily because water is less viscous than albumin.
Lipids in the form of vegetable oil in this experiment are primarily hydrocarbon structures. They tend to be poorly soluble in water. Two main types of lipids occur in biological membranes: phospholipids and sterols. Phospholipid molecules are said to be amphipathic, having ambivalent feelings. The polar head group of the molecule is intrinsically soluble...