beet cells & stress

Topics: Cell membrane, Cell, Vacuole Pages: 17 (1248 words) Published: April 20, 2014


Anatomy Physiology 1


Report 1


April 6, 2014




 Uncharged molecules can diffuse across cell membranes while some substances


must be transported across the membrane by proteins. The membrane is in control of


what enters and leaves the cell. However, certain conditions may damage the cell


membrane’s structure. Beet cells, which are plant cells, have a water-soluble pigment


called betacyanin, which is stored in its vacuole. The tonoplast, or the vacuole’s


membrane, acts with the cell membrane of the cell to prevent the betacyanin from leaking


into the cytosol or out of the cell. This lab investigates the environmental possibilities


that can damage membranes. Hypertonic and hypotonic salt solutions place stress on cell


membranes, detergents make lipids more water-soluble and disrupt membranes, and


acidic and basic pH’s denature proteins and change the color of the betacyanin. The


spectrophotometer will record the absorbance of the betacyanin leakage. The more


betacyanin leakage the more the solution will absorb light. Membrane damage increases


as the solution gets treated with higher pH and salt concentrations. The experiment


supported our hypothesis since higher levels of pH and salt concentrations resulted in an


increased release of betacyanin.








 Cell membranes are functionally important because they separate and organize


chemicals and reactions within cells by allowing selective passage of materials across


their boundaries. Cell membranes are selectively permeable. The cell membrane has a


phospholipid layer, with the polar, hydrophilic heads pointing out at the extracellular and


intracellular aqueous environment and the nonpolar, hydrophobic heads pointing inward,


protected from the water. Membranes surround both cells themselves as well as the


organelles within cells.  For example, vacuoles are surrounded by a vacuolar membrane


called the tonoplast.  The plasma surrounds the entire cell membrane. Charged molecules


can only cross the membrane with help via carrier proteins and pumps. These ionic


compounds need energy through active or passive transports or a concentration gradient


to get across the membrane.


 Many reasons can cause the damage of cell membranes, which include


concentration gradients, pH, and detergent. Beta vulgaris or the roots of beet, carry large


amounts of water-soluble reddish pigment called betacyanin. It is located almost entirely


in the large central vacuoles of cells. In intact, undamaged cells, betacyanin remains


inside the vacuole, not being able to pass through the tonoplast. Sources of stress can


cause betacyanin to leak through both the tonoplast and plasma membrane.  This leakage


will produce a red color in the water surrounding the stressed beet cells.  The amount of


leakage can be related to the degree of membrane damage.


 The stress agents each have its role in damaging the cell membrane and allowing


the red pigment to leak out. Hypertonic and hypotonic salt solutions place stress on cell


membranes. As the salt percentage increases in the solution making it hypertonic the cell


shrivels damaging its membrane. As the salt concentrations decrease in the solution


making it hypotonic, the cell expands and explodes damaging the membrane. Different


pH levels also damage cell membranes. Higher acidity will result in denaturing


membranes. Even detergent being a basic solution will disrupt the function of the cell


membrane changing the reddish color of betacyanin as well. As a result the degree of


damage can be directly related to the intensity of...

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