The Effect of Cholesterol on Membrane Fluidity Essay

990 Words 4 Pages
The cell plasma membrane, a bilayer structure composed mainly of phospholipids, is characterized by its fluidity. Membrane fluidity, as well as being affected by lipid and protein composition and temperature (Purdy et al. 2005), is regulated by its cholesterol concentration (Harby 2001, McLaurin 2002). Cholesterol is a special type of lipid, known as a steroid, formed by a polar OH headgroup and a single hydrocarbon tail (Wikipedia 2005, Diwan 2005). Like its fellow membrane lipids, cholesterol arranges itself in the same direction; its polar head is lined up with the polar headgroups of the phospholipid molecules (Spurger 2002). The stiffening and decreasing permeability of the bilayer that results from including cholesterol …show more content…
2005), addition of cholesterol may affect cell survival and membrane fluidity. After cholesterol was added to the membranes of CHO cells and bull sperm, its effect on plasma membrane fluidity and cell survival were observed when cells were either cooled to 5°C or cryopreserved (Purdy et al. 2005).

Cholesterol was added to the CHO and sperm samples in the form of 0, 1.5 or 5.0 mg cholesterol-loaded-cyclodextrin (CLC) at 23°C. Following this treatment, flow cytometry, a technique used to recognize and sort cells by first staining them with fluorescent dye, then detecting the fluorescence using laser beam illumination (Lexico Publishing Group, LLC. 2005), was used to determine membrane fluidity (Purdy et al. 2005). This technique was conducted under three different conditions: cells were treated first at 23°C, then after being cooled to 5 °C, and finally after cryopreservation and re-thawing to 23°C. Cooling of the cells was performed by placing the samples in a cold room at 5°C, while cryopreservation was done using a -70°C mechanical freezer and storage of the samples in liquid nitrogen (Purdy et al. 2005)

Essentially, the results of Purdy et al.'s (2005) experiment simply reconfirm the already widely accepted value of cholesterol as a membrane fluidity regulator. Although the addition of cholesterol did not result in more CHO cells surviving cryopresrvation,
Open Document