The purpose of this lab is to study how membranes of plant and animal cells react when exposed to different solutions. The first experiment involves purple onion skin and the second involves rat blood in various solutions. I needed to understand certain terms before preforming this lab to be able to efficiently explain what is happening to the cells. Diffusion is the tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area. Facilitated diffusion is the spontaneous passage of molecules and ions bound to a specific carrier protein across a biological membrane down their concentration gradient. Active transport is the movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins. Osmosis is the diffusion of water across a selectively permeable membrane. A hypotonic solution is a solution with a lower solute concentration when comparing two solutions. An isotonic solution is a solution having the same solute concentration as another solute. A hypertonic solution is the solution with the greater solute concentration when comparing two solutions. A selectively permeable membrane is a property of biological membranes that allow some substances to cross more easily than others. A semi-permeable membrane is a membrane that will allow certain molecules or ions to pass through it by diffusion. I also gained a better understanding of the plasma membrane. “the plasma membrane functions as a selective barrier that allows sufficient passage of oxygen, nutrients and wastes to service the entire volume of the cells” (Campbelle & Reece,2005,p.99). The plasma membrane consists of two hydrophilic regions and a hydrophobic region. There are two layers of phospholipids with the phospholipid heads facing opposite directions, with the tails sandwiched between. The plasma membrane also contains...
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