Lab 7 - Photosynthesis PDF

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BIOS 210, Spring 2021

Lab 7 Worksheet: Photosynthesis Nam

-ID: 1888

Section: 1

Date: 3/11/21

NOTE: PLEASE USE THIS WORKSHEET AS A GUIDE ONLY! Exercise 7.1: Separating photosynthetic pigments For this exercise, click on the following link and watch this youtube videos. It is a less than 4 minutes video. Copy the table below to your lab manual fill out the retention Answer the questions in your lab manual https://www.youtube.com/watch?v=ej2zXOwASVI&t=119s Solvent front Pigment D

Pigment C Pigment B

Pigment A

Ignore this

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BIOS 210, Spring 2021

PIGMENT

DISTANCE TRAVELLED FROM ORIGIN(cm)

RETENTION FACTOR

A

5.80

0.58

B

6.80

0.68

C

7.60

0.76

D

9.70

0.97

(Rf)

1. Describe the sequence of colors on your chromatography paper. List them from the origin to the solvent front. The colors are spread out on the chromatography paper. It starts from orange to lime green to green to yellow, and then a clear color at the solvent front. 2. Recall that the chromatrography paper is polar, and the solvent is nonpolar. What does this indicate about the polarity of these photosynthetic pigments? The main pigments are more polar than the accessory pigments. Chlorophyll b is the most polar pigment, so it will be the least soluble in the solvent. Chlorophyll is less polar, so it will have a middle solubility. Carotene is the least polar so it will be the most soluble. Xanthophyll are more polar than carotene. The most soluble one travels up the farthest on the chromatrography paper. Accessory pigments don’t directly participate in photosynthesis but can transfer the energy to chlorophyll. Exercise 7.2: Absorption of light by chlorophyll

For this exercise, click on the following link and watch this youtube videos. It is a less than 2 minutes video. Answer the questions in your lab manual 2 This worksheet contains copyright material. DO NOT reproduce or share with anyone not registered to BIOS 210 course at NIU.

BIOS 210, Spring 2021

https://www.youtube.com/watch?v=PMJOVqKyZsE 3. Describe what you see through the spectroscope when looking at a source of white light (i.e., the lamp). Which colors of the spectrum are visible? I see colors. Red, orange, yellow, green, blue, indigo, and violet 4. How does the spectrum of visible light change when the light is passed through the spinach extract? Why does this happen? The spectrum changes because the plant can absorb some of the light waves, so the plant can reflect all the light that you can see going through prism. 5. Which colors of light are absorbed by chlorophyll? Which colors are transmitted? Chlorophyll absorbs blue and red. Green is transmitted.

Exercise 7.3: Absorption spectra of photosynthetic pigments For this exercise, each column in the table below is color coded, obtain the absorbance reading corresponding to the color coding from the spectrophotometer reading below. For example the color of 400mm in the table is BLUE, go to the spectrophotometer and look for the blue colored arrow and obtain the reading. Repeat this step for subsequent values in the table. After completing the table Number 6 and plot the graph Number 7. You will be using only one pigment,hence, ignore the last 3 columns in your table.

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BIOS 210, Spring 2021

Wavelength (nm)

Absorbance of Photosynthetic Pigments (Chlorophyll a)

400

1.1

420

0.8

440

2.0

460

1.5

480

1.1

500

0.1

520

0.1

540

0.1

560

0.1

580

0.1

600

0.1

620

0.5

640

1.1

660

1.5

680

1.1

700

0.1

7. Graph – plot absorbance (y-axis) versus wavelength (x-axis)

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8. How do the absorbance spectra compare to each other? How would this affect a plant's ability to photosynthesize? The spectrometer is used to produce wavelengths because different compounds absorb best at different wavelengths. Some wavelengths have the same absorbance such as 500 – 600 nm have the same absorbance of 0.1. The rate of photosynthesis is affected by the different wavelengths of a light a plant is exposed to because different pigments in chloroplasts absorb different wavelengths.

Exercise 7.4: The Hill reaction For this experiment, please read through your lab manual to understand the steps that would be taken in the lab to complete this experiment. Once you’ve done that, watch the following video clip to better understand this process. Compared to the manual, This video has a slight difference, the DCPIP was not added to all the tubes, but its still the same concept tested.Once completed, review the tubes below and record their color int table number 9 in your lab manual. Then answer all questions in lab manual.

https://www.youtube.com/watch?v=JBQANaPMGao&t=495s 2

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BIOS 210, Spring 2021

No Chloroplast + White light

Chloroplast + No light

chloroplast + Red light

chloroplast + Blue light

chloroplast + Green light

chloroplast + White light

9. Record your data in the table below.

10. Where was the dye reduced? How do you know? The dye was reduced in the tubes that there results were green. I know this because green is a reduced form. 11. How did the color influence the results? Relate these results back to what you previously learned about photosynthetic pigments. The color influenced the results because the dyes can change color when reduced. 12. How does the Hill reaction compare with the mitochondrial experiment (involving succinic dehydrogenase) you examined earlier? What in that experiment was analogous to the light in this experiment? Does reduction require an energy source? In the Hill reaction, light causes chlorophyll to photo-oxidize. In the mitochondrial experiment, ATP is the basic source energy for all the reactions in a cell and this is used to produce light. Plants use the energy from the sun. 6 This worksheet contains copyright material. DO NOT reproduce or share with anyone not registered to BIOS 210 course at NIU.

BIOS 210, Spring 2021 Reduction does require an energy source because for example if the fuel is reduced to start with, this means that more energy can be gotten from it if we fully oxidize it.

Exercise 7.5: The Uptake of CO2 For this exercise, there are two videos, the first video shows the color change observed when you blow air containing CO2 into a beaker containg phenol red, this solution is then splitted into two test tubes and elodea plant placed in one test tube and wait for 30mins. The second video shows the resulting color changes in tube containing elodea leaf and testube without an elodea leaf, observe the color changes and answer the questions in your manual. https://www.youtube.com/watch?v=jZfPY3WIITo https://www.youtube.com/watch?v=8IsRY1y6DWs 13. What color is the pH indicator in acidic solutions? In basic solutions? The indicator phenol red is yellow in acidic solutions, but red in basic solutions. 14. Why did the color of the solution change when you blew into it? The color changed because it’s introducing carbon dioxide to the mix. 15. Why did the color change when the Elodea (or algae) was added to the solution? Explain your answer. The color changed because Elodea performs photosynthesis and taking up the carbon dioxide from the solution. 16. How might the color of the light source influence the rate of photosynthesis? Explain your answer. The color of the light source might influence the rate of photosynthesis because chlorophyll (has a green pigment) absorbs light required to convert carbon dioxide and water to glucose.

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