Effects Of Temperature On Plasma Membrane Stability Biology Essay

Cell membranes are indispensable for commanding the internal environment of the cell in peculiar in response to alterations in H2O potency. Cell membranes are sensitive to temperature alteration ; cold temperatures cause a stage displacement from a fluid province to a gel whereas high temperatures cause increased fluidness which increases the hazard of hosts organizing. Betacyanin, a ruddy pigment stored within the vacuoles of Beetroot ( Beta vulgaris ) is released when membrane unity is compromised. The grade of escape into a bathing solution can give a comparative step of membrane stableness. Summer and winter grown Beta vulgaris rubra discs were suspended in distilled H2O over a scope of temperatures. These were compared against Beta vulgaris rubra in solutions of 0.05mM CaCl2 and 500mM saccharose ( -192-40A°C ) and the soaking up of the bathing fluid was assayed in a spectrophotometer ( 540nm ) to measure the extent of membrane break. Significant break was found at temperatures & lt ; 0A°C and & gt ; 30A°C in both winter and summer Beta vulgaris rubra. No important difference in winter/summer ( p & gt ; 0.9 ) Beta vulgaris rubra was found nevertheless, possible differences in optimal membrane stableness ( 0-10A°C and 10-30A°C ) were identified. No important consequences were found in checks comparing saccharose or CaCl2 to H2O solutions. Research suggests that Beta vulgaris rubra may be able to set their biochemistry to subtly alter the temperature of optimal membrane stableness and this may bespeak an chance to selectively engender temperature immune Beta vulgaris rubra.


Cell membranes are constructed from aliphatic phospholipids that separate the internal and external environment. They are keeping the differences between the extracellular and cytosolic environment whether through endocytosis or active conveyance of necessary molecules or through the ejection and defense mechanism against harmful chemicals e.g. Na. they are built-in to the cell reacting to the external environment and protecting valuable cell contents e.g. proteins.

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At low temperatures the membrane goes through a stage alteration from a liquid ( fluid ) province to a planar stiff crystalline ( gel ) province. This causes the two beds of the plasma membrane to divide, this causes membrane escape. Membranes with higher proportions of unsaturated phospholipids freezing at a lower temperature, so holding an increased concentration of unsaturated fatty acids can better hoar tolerance in workss. Cis-doubled bonded fatty acids have kinked hydrophobic dress suits, this increases the distance between the phospholipids and reduces the interaction between the hydrocarbon talk domains. This in bend, makes the membrane more hard to stop dead. To forestall the membrane altering province a works can bring forth enzymes that can change the unsaturated phospholipid content of their membranes ( Makarenko, 2007 ) . An array of proteins, AFPs ( Antifreeze Proteins ) , have been found to be upregulated/only produced in workss exposed to cold ( Guy, 1990 ) . Although these proteins remain largely unidentified it is thought they may forestall intracellular ice formation or act as protein stabilizers. These proteins are sometimes associated with drouth inducible cistrons e.g. 1s associated with abscisic acid.

Excess heat causes plasma membranes to go progressively unstable increasing the hazard of organizing lesions within the membrane. In add-on high temperatures can besides do flowering and denaturing of proteins within the cell. However, many works cells produce protein chaperones or ‘heat-shock proteins ‘ which can re-fold proteins back into their original constellation at higher temperatures ( Hendrick 1993 ) . It is thought that heat-resistant workss may besides utilize ‘stabilisers ‘ such as ions e.g. Ca+ to maintain proteins in the right agreement. This is based on grounds that many thermophiles do non react every bit good to their usual optimal temperature in vivo as opposed to in vitro. It has besides been shown that enzymes within heat immune workss have a higher optimum/Amax ( Hayashi 2001 )

Sucrose has been shown to increase stableness of membranes when subjected to cold temperatures ( Lineburger 1979 ) It has been suggested that this could be due to an addition in the concentration of harmful compounds/ions e.g. Na ions as extracellular ice crystals can do desiccation of the cell ( Shinozaki 2000 ) ( Lovelock 1953 ) or that it could be due to the sugar somehow blocks the active sites or other sensitive countries of the membrane ( Santiamus 1971 ) . Alternatively it could be due to the sugar doing a structural alteration in the membrane ‘s constellation ( Williams 1970 ) .

Beta vulgaris ( Beetroot ) is a root veggie with a distinguishable ruddy coloring conferred by the compound betacyanin, a glycoside, which is stored within the cell vacuole. When the membranes of the cell are disrupted the betacyanin leaks into the environing fluid. The sum of betacyanin released into the bathing solution, which can so be assayed utilizing a spectrophotometer indicates the grade of membrane harm the cells have sustained.


Beetroot ( Beta vulgaris ) discs were suspended in solution so placed within a H2O bath. After 20 proceedingss the optical density of the solution was assayed with a spectrophotometer at 540nm. This process was performed on both summer and winter adult Beta vulgaris suspended in distilled H2O to give their optical density. Using the same process, summer grown Beta vulgaris discs were besides suspended in either a 0.5mM CaCl2 solution or 500mM glucose solution at -192, 0 and 40A°C. However, during the -192A°C conditions the process differed in that Beta vulgaris discs were frozen by liquid N so ground up and defrosted in 10ml of H2O before soaking up was read. Each status was repeated three times and the mean was found of the consequences. The consequences of the summer and winter Beta vulgaris rubra were compared utilizing a homoscedastic t-test. The consequences of the CaCl2 and sucrose conditions were besides compared against the original summer Beta vulgaris rubra suspended in distilled H2O with a homoscedastic t-test to place significance. The consequences were plotted on two spread graphs ( fig.1-2 ) with multinomial ( x2 ) tendency line.


Both summer and winter grown Beta vulgaris rubra showed an initial rise in membrane stableness between -10A°C and ( from 0.85-0.59 and 0.59-0.21 ) and so membrane stableness fell in both conditions between 20-40A°C. The tendency lines in Fig1. show that summer Beta vulgaris membrane was most stable between 10-30A°C whereas winter Beta vulgaris was most stable at a lower 0-10A°C. After these more stable temperature ranges the membrane stableness suffered significantly, for illustration in winter Beta vulgaris the difference of the mean of optical density readings at 10,20 and 30A°C differ merely by 0.09 whereas the difference between 30 and 55A°C is 0.63. A T-test showed no important difference between the winter and summer grown Beta vulgaris rubra ( p & gt ; 0.9 ) . A homoscedastic T-test was used as the discrepancy of the informations within the two populations was the same at 0.09.

Figure 1: A comparing of membrane stableness of winter and summer grown Beta vulgaris rubra ( Beta vulgaris ) membrane between -10 and 55A°C. Beetroot discs ( 4 per check ) were suspended in distilled H2O for 20 proceedingss at the specified temperature, the solution of the environing solution once the discs were discarded, was measured for optical density. Greater optical density suggests greater sum of betacyanin escape and hence greater membrane instability. Each point represents the mean of 3 measurings +/- S.D. Homoscedastic T-test indicated that the optical density was non significantly different between the two samples ( P & gt ; 0.9 ) .

Figure 2 A comparing of summer grown Beta vulgaris ( Beta vulgaris ) responses to temperature while suspended in distilled H2O, 0.5mM CaCl2 or 500mM sucrose solution. Each point represents the mean of 3 consequences. Points excluded from the graph include the values for -196A°C where the optical density was 1.99 for both sucrose and CaCl2 status proposing a entire loss of membrane unity. T-test ( including consequences non shown ) indicated there was no important difference between the 3 conditions. ( sucrose- P & gt ; 0.80 and CaCl2 – P & gt ; 0.88 )

Both CaCl2 and Sucrose showed at -196A°C to hold maximal optical density ( 1.99 ) this suggests that freeze-thawing caused a important loss of membrane unity leting a big sum of betacyanin to be released into solution. The graph suggests that Beta vulgaris rubra discs treated with 500mM sucrose retain a greater degree of membrane unity at lower temperatures ( 0.39 at 0A°C as opposed to 0.58/0.59 for CaCl2 and H2O severally ) .


The comparing of summer and winter grown sugar Beta vulgaris membrane stableness ( consequences shown in fig.1 ) show a non-statistically important difference in membrane response to temperature nevertheless, the T-test assumes each point to be independent nevertheless, the parabolic construction in Fig 1. suggests mutuality therefore, the values returned from the T-test may non wholly reflect the implicit in phenomena- peculiarly if that phenomena were to be elusive. Similarly, mistake bars in fig. 1 assume that the distribution exhibits equal discrepancy across nevertheless, this may non be the instance, for illustration at high/low temperature the discrepancy may be more fickle – except for possibly at a critical stage alteration point for Beta vulgaris rubra where the discrepancy would be really low.

The tendency line suggests different optimal temperature for each of the membranes ( winter: 3.3A°C and summer: 20A°C ) . The average dirt ( 30cm deep ) in the West Midlands ( UK ) during winter is 4-6A°C and during summer is 14-17A°C[ 1 ]. The Beta vulgaris rubra grown in the winter could hold acclimatised to the colder temperature and switched on/upregulated cistrons associated with cold response for illustration, cistrons for the production of fatty acid desaturases which could increase the fluidness of the membrane at these temperatures. Alternatively or possibly in concurrence with constitutively bring forthing AFPs which could explicate the difference between summer and winter adult Beta vulgaris rubra within the scope of 0-10A°C. A greater figure of repetitions and the inclusion of intermediary temperatures would be able to clear up whether there is so a elusive difference in the membrane response dependant on turning conditions. To demo this possibly a microarray could be used to place protein production differences in summer and winter adult Beta vulgaris rubra.

Similarly, the informations within the fig 2. is non statistically important, nevertheless, this is non surprising given the deficient figure of intermediary temperatures. The mistake bars of the summer grown Beta vulgaris are moderately big and so encompass both the CaCl2 and sucrose conditions. This could be clarified with farther tests. Both the CaCl2 and sucrose status showed maximal soaking up when freezing thawed at -196A°C proposing that at such temperatures neither solution can maintain the membrane stable.

This research suggests that Beta vulgaris rubra should non be grown until & lt ; 0A°C temperatures for the twelvemonth have passed as the Beta vulgaris rubra assayed showed a important addition in the sum of betacyanin released than at temperatures between 10-20 A°C. It besides suggests that Beetroot can potentially accommodate to a grade to somewhat lower average temperatures. Engendering programmes that highlight the qualities of the winter adult Beta vulgaris rubra might assist in take downing the membrane stage displacement point and hence increase output in locations where it can non presently grow good.