Biology+Practical+Sessions

= Biology Practical Sessions = Agar Experiment AIM: The aim of the experiment is to find how the exposed surface area of the same volume of agar will affect the rate of conductivity.

HYPOTHESIS: The larger the exposed surface area, the higher the rate of conductivity. The smaller the exposed surface area, the lower the rate of conductivity.

APPARATUS:  METHOD:
 * Razor blade/ Scalpel
 * White tile
 * Ruler
 * Glass rod
 * Stop watch
 * 3 beakers
 * 3 pieces of 2x2x2 cm3 solid agar
 * Data logger with conductivity probe
 * 1) Cut one of the solid agar blocks into 8 cubes such that each side is 1cm in length using the white tile.
 * 2) Cut another of the large agar cubes into 64 cubes such that each side is 0.5cm in length on the white tile.
 * 3) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Set up the data logger.
 * 4) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Fill a beaker with 200ml of tap water and place the conductivity probe in the water.
 * 5) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Starting with the largest agar block, place it in the beaker and start recording conductivity readings on the data logger, starting the timing on the stopwatch at the same time.
 * 6) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Stir the water with the glass rod continuously and gently.
 * 7) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">After 2 minutes, stop the data recording and record the change in reading.
 * 8) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Record the highest conductivity read from the graph shown in the data logger.
 * 9) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Repeat steps 5 to 8 for the 1x1x1 cm3 cubes and then the 0.5x0.5x0.5 cm3 cubes.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">RESULTS:

(cm) || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Surface area (cm2) || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Volume (cm3) || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Surface area to volume ratio || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Surface area divided by volume || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Rate of conductivity change ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">No. of pieces of agar cubes || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Length
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">1 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">2 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">24 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">24:8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">3 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">+0.55 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">1 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">6 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">6:8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">0.75 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">-0.30 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">64 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">0.5 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">1.5 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">1.5:8 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">0.1875 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">+2.35 ||

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;"> ANALYSIS: The change in the rate of conductivity in the water for the single large agar block was +0.55, -0.30 for the 8 medium blocks, and +2.35 for the 64 small blocks.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">The single agar block could have a lower conductivity rate as it had a higher surface area exposed to the water compared to the 8 medium blocks and 64 small blocks. As it had a higher surface area, and hence a higher surface area to volume ratio, there would be higher exposure and more of the agar would diffuse out of the block into the water and hence, the conductivity level of the water would increase as some the agar had diffused out from the block and affected the conductivity of the water. (Diffusion is the movement of particles from a region of high concentration to a region of low concentration.)

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">For the 8 medium blocks, they had a lower surface area than the single agar block and a lower surface area to volume ratio so a lower surface area would be exposed to the water and less of the agar would diffuse into the water during the time period of 2 minutes and hence it had a negative change in conductivity rate that indicates that

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">As for the 64 small blocks, they had the lowest surface area and the lowest surface area to volume ratio and hence less of the agar would diffuse out of the block and hence the conductivity of the water would increase.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">DISCUSSION QUESTIONS:
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">What precautions did you take in the experiment?
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">My partner and I ensured that each cell was of the correct measurement, and that we stirred the water with the strength each time so the conductivity readings were only affected by the surface area of the agar cells.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">- The lower the surface area, the higher the conductivity.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">What can you infer from the results above?

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">- The graphs tell me that the rate of diffusion increases with the surface area of the agar and decreases with it too.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">What do the graphs reveal to you about the rate of diffusion and the surface area of the agar?

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">- I think the experiment in Lower Secondary was more accurate as this experiment depended upon the strength of the stirring which could defer due to human error and would definitely negatively affect the results of the experiment in terms of accuracy.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Compare this experiment with the one that you did in Lower Secondary where coloured agars were soaked in acid. Which do you think is more accurate?

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">- The large block is the most efficient.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Examine the agar cells below and work out the surfaced area to volume ratio of each cell. Which is most efficient and which is least?

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 117%;">Beetroot Experiment <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">AIM: The aim of the experiment is to find out how two factors, the solution in which the beetroot is submerged in and the surface area of the beetroot, affects the movement of the pigment in and out of the beetroot cells which is measured by calculating the light transmission of each solution.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">HYPOTHESIS:

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">APPARATUS:
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Razor blade/scalpel
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Ruler
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">5 test tubes
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Test tube rack
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Labels
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Forceps
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Distilled water
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">25% and 50% alcohol
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Beetroot
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">White tile
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">2 petri dishes
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">3 droppers (1 for water, 1 for 25% alcohol, 1 for 50% alcohol)
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Thermometer
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Stop watch
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">2 beakers
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Supply of hot water
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Spectrophotometer (Data logger)

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">METHOD: <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">While waiting during the 15 minutes: <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">RESULTS:
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Use the ruler and scalpel to measure and cut the cylinder of beetroot into 15 discs of 2mm each using the white tile.
 * 2) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Take 3 discs of beetroot and cut them into smaller pieces.
 * 3) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Rinse the beetroot discs and pieces until the water is colourless.
 * 4) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Label and prepare 5 test tubes as follows:
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tube A: 4ml of water
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tube B: 4ml of 25% alcohol
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tube C: 4ml of 50% alcohol
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tube D: 4ml of 90-100°C hot water
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tube E: 4ml of water
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Place 3 discs of beetroot in Tube A-D each and all the smaller beetroot pieces into Tube E using the forceps.
 * 2) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Leave the tubes to stand in the rack for 15 minutes timed with the stopwatch.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Set up the data logger
 * 2) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Fill a cuvette with water up to the indicated mark.
 * 3) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Place the cuvette in the colorimeter and hold the cap closed, making sure the sides of the cuvette are clean and dry before placing it in the colorimeter.
 * 4) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Calibrate the machine by clicking the ‘run’ icon on the data logger and twisting the knob on the front of the colorimeter until the screen registers 100%.
 * 5) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> After 15 minutes are up, shake the tubes gently and hold each against the clean white tile to note the colour and record the observations for each tube in a table.
 * 6) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> Decant a small amount of liquid from Tube A into a cuvette and replace the previous cuvette with the cuvette containing liquid from Tube A.
 * 7) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> Click the ‘run’ icon to begin recording the data.
 * 8) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> Record the value of light transmission once the value shown is relatively steady.
 * 9) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> Repeat steps 12 to 14 for all test tubes and record the results in a table.
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Test tube || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Solution in the test tube || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Colour description || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">% of light transmission || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">% change in light transmission ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">A || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tap water || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Lightest, light pink || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">96 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">4 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">B || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">25% ethanol || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Slightly darker than D || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">71 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">29 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">C || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">50% ethanol || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Darkest red || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">14.5 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">85.5 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">D || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Hot water (90-100℃) || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">A darker pink than E || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">91 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">9 ||
 * <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">E || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Tap water || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Slightly darker than A || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">75 || <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">25 ||

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;"> ANALYSIS: The solution in test tube C allowed the least light to pass through, followed by B, E, D and A with the solution in test tube A allowing the most light to pass through.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">For solution B,

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">A possible explanation for the extremely low light transmission for the solution in test tube C is that the high ethanol content in the solution caused

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">For the solution in test tube D, one possible reason why it has a lower percentage of light transmission is that the heat energy from the hot water is transferred to particles in the pigment and is converted to kinetic energy causing the particles in the pigment to vibrate and move faster (according to the Brownian motion, particles are constantly vibrating and in random movement in gases and liquids or vibrate about their fixed positions in solids). Due to the increased vibration and speed in the movement of the particles in the pigment, they diffuse out of the cells quicker and hence more of the pigment would diffuse out of the beetroot cells into the hot water in the 2 minutes than if tap water was used (test tube A).

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">As for solution E, the total surface area of the beetroot that was submerged in the solution was greater than all of those used previously in the experiment. Because of an increased surface area, there would be a greater area from which the pigment could diffuse out of the cells into the tap water and would increase the speed of diffusion as more of the pigment would diffuse out of the beetroot cells than if just 2mm discs were used (test tube A) hence E has a lower light transmission percentage than solution A.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">DISCUSSION QUESTIONS: <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">- The control in this experiment was the water that was used to fill the first cuvette. <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">- First we can compare test tubes A, B, C and D because 2mm discs are used for these <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">- It is important to wash the discs and chopped pieces of beetroot before using them in the experiment because this would ensure that when the beetroot is placed in the test tube, they do not have any pigment on the surface of the discs or chopped pieces, increasing the accuracy of the results. <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">- I washed the beetroot discs and cut the discs from the same beetroot so that they were as alike as possible in the sense of size and water content of the discs. <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">- Yes,. Also, the more the alcohol, the greater the <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">What was the control in this experiment?
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">How do you analyse the results of this experiment one variable at a time?
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Why was it necessary to wash the beetroot slices thoroughly before using them in this exploration?
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">The main source of error in any biological experiment is usually the natural variation of living things. What did you do to ensure that this variation was minimised?
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">Does alcohol have an effect on beetroot cell membranes? Was the concentration of alcohol a factor too? Suggest an explanation for your observations.
 * 1) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%; letter-spacing: 0px;">What are factors you can think of that would affect the leaking of the pigment out of the beetroot cells?

INVESTIGATING THE EFFECT OF TEMPERATURE AND pH ON ENZYME ACTION

//Hypothesis// The aim of the experiment is to find out how temperature and pH levels affect enzyme action.

//Apparatus and Materials//
 * 1) Bunsen burner, tripod stand and gaue
 * 2) 3 water baths
 * 3) Thermometer
 * 4) 12 test tubes and a test tube rack
 * 5) Measuring cylinder
 * 6) 4 beakers (250ml)
 * 7) 2 white tiles
 * 8) 2 droppers
 * 9) Ice cubes
 * 10) Distilled water
 * 11) Test tube holder
 * 12) Stop watch
 * 13) Goggles
 * 14) 2% starch solution
 * 15) 1% amylase solution
 * 16) 1 M hydrochloric acid solution
 * 17) 1 M ammonium hydroxide solution
 * 18) Iodine solution

//Procedure// __Part A__
 * 1) Label 8 test tubes ‘A1’, ‘A2’, ‘B1’, ‘B2’, ‘C1’, ‘C2’, ‘D1’, ‘D2’.
 * 2) Add 5cm 3 of starch solution to tubes A1, B1, C1 and D1. Add 3cm 3 distilled water to D2, and then 3cm 3 of amylase solution into tubes A2, B2 and C2.
 * 3) Place A1 and A2 into a beaker of ice water, B1 and B2 into a water bath of temperature 37°C, and D1 and D2 into another water bath at 37°C.
 * 4) Place C1 and C2 in boiling water.
 * 5) Leave the tubes for 10 minutes to allow the solutions in the tubes to reach the temperature of the water bath.
 * 6) Pour the contents of A2, B2, C2 and D2 into the starch tube, A1, B1, C1 and D1, next to it. Record the time immediately. Keep the tubes A1, B1, C1 and D1, containing the mixture in the respective water bath throughout the experiment and ensure that the temperatures are maintained.
 * 7) After 10 minutes, test the mixture in each tube with iodine solution on a white tile. Draw table 1 with appropriate headings and record the results and conclusions.

__Part B__
 * 1) To each of the 4 test tubes, W, X, Y and Z, add 2cm 3 of starch solution. Place the tubes in a water bath of temperature 37°C.
 * 2) Make up the contents of the 4 test tubes as shown in table 2.
 * 3) Test the solution with iodine solution at the beginning of the experiment and after 10 minutes.
 * 4) Record your observations and conclusions in table 2 below.

//Results// Table 1

**Test tube** || **Results of iodine test** || A1 and A2 || Solution remained brown || B1 and B2 || Solution remained brown || C1 and C2 || Solution turned blue-black || D1 and D2 || Solution turned blue-black ||

Table 2

**Test tube** || **Contents** || **Iodine test before experiment** || **Iodine test after experiment** || **Conclusion** || W || 2cm 3 of starch solution + 2cm 3 of hydrochloric acid + 2cm 3 of amylase solution || Turned blue-black || Turned blue-black || Amount of starch present in solution remained the same || X || 2cm 3 of starch solution + 2cm 3 of distilled water + 2cm 3 of amylase solution || Turned blue-black || Remained brown || Amount of starch present in solution was reduced || Y || 2cm 3 of starch solution + 2cm 3 of ammonium hydroxide + 2cm 3 of amylase solution || Turned blue-black || Turned blue-black || Amount of starch present in solution remained the same || Z || 2cm 3 of starch solution + 4cm 3 of distilled water || Turned blue-black || Remained brown || Amount of starch present in solution was reduced ||

//Interpreting the Results// __Part A__ A1+A2 and B1+B2. The iodine test shows that starch was absent in the solution after the experiment because the solution remained brown, hence indicating that starch digestion occurred. C1+C2 and D1+D2. The conditions that the starch and enzyme mixture were under were not conducive for an enzyme reaction to take place in. It serves as a control for the experiment. Benedict’s test for reducing sugar. This test is used to reduce sugar and also indicates the amount of sugar reduced from the colour of the precipitate formed. 2cm 3 of the solution to be tested and 2cm 3 of Benedict’s solution is to be added into a test tube and shaken. Heat the test tube in a boiling water bath for 5 minutes, noting the colour changes taking place in the test tube. If the a precipitate of a green, yellow, orange or red colour is formed, sugar was present in the solution. If not, sugar was not present in the solution. The optimum temperature for enzyme action is 37°C, approximately body temperature, and cold temperatures as indicated by test tubes A1+A2 placed in the beaker of ice water.
 * 1) Which tube shows that starch digestion has occurred? Give your reasons.
 * 1) Which of the test tubes contained mixtures that gave a blue-black colour?
 * 1) Why did the mixtures In the tubes stated in question 2 remain blue-black?
 * 1) What purpose does the tube D1 serve?
 * 1) Using your knowledge of the structure of starch, describe the test you would use to detect the presence of the substance produced as a result of the reaction in the test tubes stated in question 1 above?
 * 1) What conclusion(s), based on the observations in this experiment, can be made about the effect of temperature on enzyme action?

__Part B__ X and Z. The results of the iodine tests for these 2 test tubes showed that there was no starch present in the solution after the experiment while starch was present in the solution before the experiment as the iodine turned blue-black before but after the experiment, it remained brown, hence indicating that starch digestion had occurred. W and Y. The high and low pH levels of these two test tubes prevented any enzyme action from taking place, and hence preventing any digestion of starch, therefore starch was still present in the solution after the experiment and the iodine turned blue-black. A neutral pH is the optimum pH level for enzyme action to take place, while a lower or higher pH level prevents enzyme action from taking place. The higher or lower the pH level is from the neutral level, the lesser the enzyme action that occurs.
 * 1) Which tube shows that starch digestion has occurred? Give your reasons.
 * 1) Which of the test tubes contained mixtures that gave a blue-black colour?
 * 1) Why did the mixtures in tube stated in question 2 remain blue-black?
 * 1) What conclusion(s), based on the observations in this experiment, can be made about the affect of pH on enzyme action?
 * 1) How does the temperature and pH affect enzyme action?