Dialysis and Osmosis Lab
Holy Trinity Catholic Secondary School
Tuesday, February 17th, 2015
Introduction: The cell membrane is not a solid structure. It is made of millions of smaller molecules that create a flexible container. Proteins and phospholipids make up most of the membrane structure. “The proteins are found around the holes and help move molecules in and out of the cell. There are also proteins attached to the inner and outer surfaces of the membrane” (BiologyKids, 15). There are receptor proteins which receive specific molecules, and there are transport proteins. There are two types of transport proteins which only allow specific molecules to enter and exits, therefore selectively permeable. Releasing chemicals is called Exocytosis, and taking in chemicals is endocytosis.
“Scientists use the fluid mosaic model to describe the organization of phospholipids and proteins. The model shows you that phospholipid molecules are shaped with a head and a tail region. The head section of the molecule likes water (hydrophilic) while the tail does not (hydrophobic). Because the tails want to avoid water, they tend to stick to each other and let the heads face the watery (aqueous) areas inside and outside of the cell” (BiologyKids, 15). The two surfaces of molecules create the lipid bilayer. The interior of the lipid bilayer is “oily” and flexible like a soap bubble.
Osmosis is the diffusion of water across a selectively permeable membrane, which is a barrier that has holes large enough to allow water molecules to pass but small enough to block certain molecules like salt or glucose. “Water with solutes (substance dissolved in water) diffuses from an area of lower concentration of solutes to an area of higher concentration until the concentrations on both sides of the membrane are equal” (DiffsionBio, 15). Osmosis is of great importance in biological processes where...