Membrane Permeability Essay

2770 words - 11 pages

Investigating the effects of temperature and ethanol concentration on membrane permeabilityCellular membranes are vital to the function of all cell types. Cellular membranes are selectively permeable, allowing the cell to regulate the transport of substances in and out of the cell. The fluid mosaic model considers membranes to be composed of a phospholipid bilayer with associated proteins (Linder, 2009). Phospholipids are amphoteric molecules with a hydrophilic (water loving) head and hydrophobic (water resisting) tail (Linder, 2009). Associated membrane proteins form a number of roles such as the formation of channels.Cell membranes are selectively permeable barriers (Linder, 2009). Together with proteins, water-soluble molecules are excluded from entering the cell, but permits lipid soluble molecules such as O2, CO2 and alcohol to pass freely through the membrane (Heller, Schaefer, & Schulten, 1993).Vacuoles are organelles found in plants, bacterial, fungal, protists and some animal cells (IHW , 2004). The organelle is protected by a cell membrane and its general function is to maintain internal hydrostatic pressure or turgor within cells (Encyclopedia , 2004 ). The vacuole of beetroot plants contains a water-soluble red pigment called betacyanin (IHW , 2004). When the cells remain in a healthy state, the pigment does not leak through, and remains within the vacuole (Linder, 2009). However when cell membranes are destroyed, the permeability of the tonoplast is damaged causing the betacyanin to leak out from the vacuole and produce a dark pink/red color in the surrounding water (IHW , 2004). Extensive studies have shown that intrinsic membrane proteins, such as ion and water channels are strongly affected from the small changes made within to composition of the cell membrane. Changes in environment, temperature and the influence of alcohol significantly affect membrane permeability, and may lead to cell death (Karp, 2001).Ethanol found in most alcoholic substances interacts with biological membranes, which previous studies have shown that it significantly decreases the levels of membrane integrity (Pantra & Salonen, 2008). Ethanol is lipophilic, and can enter the cell very easily and interferes with the mechanical properties of permeability and diffusion (Westminister College, 2011). This can cause intrinsic proteins such as ion and water channels that regulate the chemical and physical balance in cells to be disturbed. As structure is changed, the membrane increases in permeability, which affects the membranes signaling. Ethanol forms hydrogen bonds that come between the structures of water thus, disrupting its organization (Westminister College, 2011). This leads to the interaction between the hydrophilic end of the membrane and water being disrupted (Pantra & Salonen, 2008).The fluidity of cell membranes also allows the organisms to respond to various environmental changes such as temperature. If temperatures exceed optimum...

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