Worksheet for the LR2 Submission PDF

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It is the lab report for light reactions....

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Name __________________Kabita Kunwar_________ Section _____BY 373-001_______

WORKSHEET FOR CHAPTER 6 INVESTIGATING THE LIGHT REACTIONS OF PHOTOSYNTHESIS A. Calibration of the spectrophotometer. This will be done only once by one person. B. Procedure 1. Determining the photosynthetic activity of isolated chloroplast. 1. Obtain a cuvette and add the reaction components as follow: a. 2 ml of buffer. b. 200 microliters DCPIP c. 200 microliter chloroplast suspension 2. Cover with a piece of plastic (Parafilm) and invert once to mix. 3. Wasting no time, insert in the spec and record the A600 4. Take your cuvette to 20 cm distance from a light source for 1 minute and then record the A600. 5. Repeat the light exposure for 5 minutes 6. Record your data in the table 2 below Table 1. Time t=1 t=2 t=3 t=4 t=5 Change of A600/min

A600 0.45 0.33 0.22 0.16 0.08 -0.0925

1. Use Excel or the graph paper provided and graph the change of A600 over time from the table above. 2. Determine the change of absorbance/min from the time 1 =1 to time t = 5 minutes or from the graph Ans.: __

Δ y y 2 − y 1 0.08−0.45 −0.37 = = =−0.0925 = 4 5−1 Δ x x 2−x 1

A600 vs Time 0.5 0.45 0.4

C. Procedure 3: Effects of herbicide on chloroplasts activity 1. Obtain a cuvette and add the reaction components as follow: a. 1.9 ml of buffer. b. 0.1 ml (100 microliters) of the herbicide 2,4-D c. 200 microliters DCPIP d. 200 microliter chloroplast suspension 2. Cover with a piece of plastic (Parafilm) and invert once to mix. 3. Wasting no time, insert in the spec and record the A600 4. Take your cuvette to 20 cm distance from a light source for 1 minute. 5. Bring it back and record the A600. 6. Repeat the light exposure and recording the A600 for 5 minutes. 7. Record your data in the right side of table 2 below 8. For the control, copy the data of table 1 into table 2

Table 2. Effects of herbicide on the light reactions of photosynthesis

Control (from table 1) A600 0.45 0.33 0.22 0.16 0.08 -0.0925

Time t=1 t=2 t=3 t=4 t=5 Change of A600/min

With herbicide A600 0.42 0.39 0.35 0.31 0.28 -0.035

Use Excel or the graph paper provided and graph the change of A600 over time from the table above (control and effect of herbicide on the same graph). Determine the change of absorbance/min from the time 1 =1 to time t = 5 minutes or from the graphs Rate of DCPIP reduction as affected by herbicide: __ Δ y y 2 − y 1 0.28−0.42 −0.14 = = =−0.035 = 4 5−1 Δ x x 2−x 1 Rate of DCPIP reduction control _

Δ y y 2 − y 1 0.08−0.45 −0.37 = = = =−0.0925 4 5−1 Δ x x 2− x 1

A600

Effects of herbicide on light reactions 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0

1

2

3

4

5

Time Control

With Herbicide

6

7

Procedure 4. Effects of distance away from light source on the Activity of isolated chloroplasts Note: this is the same as the procedures B but at different distances from the light source. (each table will be assigned a distance away from light for their experiment) 1. Obtain a cuvette and add the reaction components as follow: a. 2 ml of buffer. b. 200 microliters DCPIP c. 200 microliter chloroplast suspension 1. Cover with a piece of plastic (Parafilm) and invert once to mix. 2. Wasting no time, insert in the spec and record the A600 3. Take your cuvette to your assigned distance from a light source for 1 minute and then record the A600. 4. Repeat the light exposure for 5 minutes 5. Record your data on the board. 6. When the whole class is done, copy the class data in the following table

Table 3. A600 nm time

20 cm

40 cm

60 cm

80 cm

100 cm

t= 1 t=2

0.45 0.33

.44 .38

0.42 0.35

0.45 0.39

0.45 0.45

t=3

0.22

0.26

0.29

0.35

0.44

t=4

0.16

0.22

0.28

0.31

0.44

t-5 Rate of DCPIP reduction (slopes)

0.08

0.19

0.27

0.28

0.43

-0.0925

-0.0625

-0.0375

-0.0425

-0.0029

7. Calculate the rates of DCPIP reduction as shown in the lab and record the slopes in the table below Table 4 Effect of Light Intensity on photosynthetic Activity

Distance (cm)

Rate A600/min.

20 40 60 80 100

-0.0925 -0.0625 -0.0375 -0.0425 -0.0029

8. Plot the results of table 4 with distance on X-axis and rates on Y-axis

Rate A600/min. 0 -0.01

0

1

2

3

4

5

6

7

Rate (A600/min)

-0.02 -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.1

Distance (cm)

What can you conclude from the graph We can conclude that the when the assigned distance is increase, the rate of absorption also increases. In conclusion: The rate of photosynthesis increases on increasing the intensity of light until the maximum intensity of light is used....