BIOLOGY PRACTICAL REPORTS FOR FORM 4 Experiment 3.6 (Practica text!""# pa$e 3%& Pr"!em Statement : What is the concentration of an external solution which is isotonic to the cell sap of plant tissue? O!'ectie : To To determine the concentration of an external solution which is isotonic to the cell sap of plant tissues. )*p"t+e,i, :When plant cells are immersed in an isotonic solution, there is no net gain in mass and size. -aria!e, manip/ate0 aria!e: concentration of sucrose solution re,p"n0in$ aria!e: mass of strips of potato c"n,tant aria!e : time of immersion of the potato strips / volume of sucrose solution used / type of plant tissue used
solutions, !" sucrose solution, tissue Materia,: potato strips, distilled water, 5sucrose solutions, paper Apparat/,: #nife, cor# $orer, ! $ea#ers %5"ml, electronic weighing scale, ruler Tec+ni1/e: record the change in mass of the potato strips that has $een immersed for & hour in different sucrose concentrations using an electronic weighing scale C"r# B"rer
P"tat" Strip
2i,tie0 ater L
S/cr",e S"/ti"n M
S/cr",e S"/ti"n
'pparatus set(up to determine the concentration of an external solution solution which is isotonic isotonic to the cell sap of plant tissues. Pr"ce0/re
&. ! $ea#ers $ea#ers were la$elled la$elled as ), * and +. ea#er ea#er ) was filled filled with distille distilled d water, water, $ea#er $ea#er * with 5 sucrose solution and $ea#er + with !" sucrose solution. %. ' cor# cor# $orer was was used to o$tain o$tain ! potato potato strips. strips. -ach strip was was cut to a length of of 5 cm. The potato strips were wiped dry using filter paper. -ach potato strip was weighed using an electronic weighing scale and the initial mass recorded in a ta$le of results.
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!. The potato strips were placed immersed in the respective sucrose solutions and left for & hour. 'fter & hour, each potato strip was ta#en out from its respective $ea#er, wiped dry and its mass weighed. The final mass was recorded in a ta$le of results. . The texture was recorded and its appearance noted. 5. The difference in mass was calculated. . ' graph of difference in mass against concentration of sucrose solution was drawn and from the graph the concentration of sucrose solution which is isotonic to the cell sap of the potato was determined. 0. Sa5et* preca/ti"n : The potato strips were wiped dry using tissue paper $efore weighing to get a more accurate mass. Re,/t,:
ea#er 1oncentration of sucrose solution ) 6istilled Water * 5 + !"
2inal 3nitial *ass/g *ass/g
difference in mass 4 2inal mass 3nitial mass x &"" 3nitial mass
Texture and appearance
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&. What is the texture and appearance of the potato strips after $eing immersed in the various concentrations of sucrose solution? %. What do the axes on your graph represent? !. 7ow do you determine the concentration of sucrose solution which is isotonic to the cell sap of the potato from your graph? . ased on the experiment, discuss the process of osmosis in the various concentrations of sucrose solutions. C"nc/,i"n
The hypothesis is accepted. When plant cells are immersed in an isotonic solution, there is no net gain in mass and size.
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