Temperture's Effect on Beet Membranes

Temperture's Effect on Beet Membranes
Aim: To investigate the effect of temperature on membrane structure Hypothesis: The higher the temperature, the greater the amount of pigment that leaves the beetroot cell. 1. An increase in temperature increases the kinetic energy of the molecules within the cell, raising the rate of diffusion of pigment out of the cell across the differentially permeable cell membrane. 2. A further increase in temperature will cause the protein molecules in the cell membrane to change shape, i.e. becoming denatured. As a result, the red pigment in the vacuole will, together with the cytoplasm, leak out through the damaged membrane. Colour leakage will hence increase more significantly. Apparatus and procedure Alterations to the procedure To wash away excess dye, the newly cut beetroot slices are not left overnight but 2 minutes only, in order to save time
Identifying variables: Independent Variable Dependant Variable Controlled Variable Temperature Colour absorbency Beetroot Diameter and length of beetroot slices Volume of water in each boiling tube Time for washing away excess dye Time for each boiling tube of water to equilibrate in each water bath Time each boiling tube of water and beetoot was left in each water bath Safety precautions 1. Take care using the knife and cork borer. 2. Wear safety goggles in case splashes of red pigment enter your eye. 3. Handle hot boiling tubes carefully. Results Temperature/?C Colour Absorbency/A 0 0.03 10 0.02 30 0.06 40 0.23 50 0.92 60 1.85 70 1.76 A graph of colour absorbency against temperature is plotted to investigate how temperature affects leakage of red pigment from the beetroot slices. A trendline is also drawn: [image] Analysis 1. At the beginning, colour absorbency increases with temperature slowly. 2. As temperature rises above 40Co, absorbency increases more rapidly. 3. When temperature rose from 60Co to 70Co, absorbency has roughly leveled and may have reached a constant. Conclusion The higher the temperature, the greater the amount of pigment that leaves the beetroot cell. There are 3 reasons: 1. Increase in temperature increases the kinetic energy of molecules, hence raises the rate of diffusion. 2. Proteins in the cell membrane are very susceptible to temperature changes. A further increase in temperature above the optimum point will change their shapes and denature them. The cell membrane is now damaged, unable to properly control transport across it. Colour leakage increases significantly. 3. When the cell membrane becomes fully permeable, the red pigment in the vacuole of the beetroot cell can move freely from the cell out to the water, hence rate of colour leak reaches a constant. Limitations 1. Different cuvettes have different colours, so the accuracy of colour absorbency was affected. 2. The newly cut beetroot slices were not put in distilled water long enough, so excess dye was not washed away thoroughly. Some pigment may have leaked out during the experiment due to broken vacuole. Improvement 1. Use the same cuvette to hold distilled water and each of the 7 samples. Make sure that the cuvette is rinsed thoroughly before pouring in a new liquid. 2. Before the experiment, leave the beaker of distilled water and beetroot slices overnight to make sure that all excess dye is washed away.

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