Concept map of photosynthesis

Concept map of photosynthesis

Refer to the concept map on the following page to answer these questions.

  1. What is the chemical species that is transferred through the light reactions? (Box A)

Answer: chlorophyll

  • What energy-rich compound is produced by the actions of the cytochrome complex? (Box B)

Answer: ATP

  • What is the compound (Box C) used to donate electrons to the photosystems, and which gives rise to 2H+ and O2?

Answer: H2O

  • What energy is used to energize the light reactions? (Box D)

Answer: Red light

  • What is the product of the reaction that is occurring at NADP+ reductase? (Box E)

Answer: NADPH+H+

  • Provide names for structures i and ii? (0.5 mark for each correct answer)

Answer: photosystem II and photosystem I respectively

Answer: NADP+

Introduction

In one paragraph (250 words or less) provide a brief introduction to your experiment (5 marks).  Use the following description and questions and the concept map on the previous page to guide you. Provide an overview of photosynthesis by describing the purpose of the light and dark reactions.  How do the light and dark reactions contribute to photosynthesis? Describe the products and by-products of the light reactions and the general concept of the system. What part of the system does the DCPIP substitute? At least 1 reference required.

Text Box: Insert text here
Photosynthesis involves the conversion of light energy by plants to the chemical form of energy which is later used in fueling plant activities. Consists of light and dark reaction phases. In the first phase, a molecule of chlorophyll in photosystem II(P680) takes in a photon and releases an electron. The electron is forwarded to pheophytin, which subsequently forwardsthe electron to a molecule of Quinone and this starts electron flow in a chain of electron transport leading to reducing of NADP to NADPH. The gradient of energy created by the above process is utilized by ATP synthase in ATP production. The molecule of chlorophyll in photosystem II gets back the electron it lost ultimately when a molecule of water is broken down by photolysis, releasing O2. the electron freed on photosystem II enters a molecule of chlorophyll(P700) in photosystem I. The electron goes through a chain of acceptors of electrons where it releases some energy. eventually the electron is used in the reduction of NADPwith H+ into NADPH, which has a key role in the dark phase. In the dark phase, RuBisCO enzyme gets atmosphericCO2, and using the Calvin cycle utilizes the already formed NADPH, releasing 3 sugars of carbon later used in forming starch and sucrose, hence food manufacture. The process of carbon fixation leads to the production of a 3C sugar product which in turn is changed into final carbohydrates.
References
Bryant, D.A., and Frigaard N.U.(2006) “Prokaryotic photosynthesis and phototrophy illuminated.” Trends inMicrobiology 14(11):488-496 doi:10.1016/J.TIM.2006.09.001. PMID16997562
Reece, J., Urry, L., Cain, M., Wasserman, S., Minosky, P. and Jackson, R. (2011) Biology (International ed) Pearson Education.pp235, ISBN 978-0-321-73975-9

Hypothesis

In 50 words or less, state the hypothesis of the experiment.

Text Box: Insert text here
To measure the rate at which photochemical reactions occur using color changes observed in DCPIP


Methods

In one paragraph, (250 words or less) describe your experimental procedure. Include a description of the experimental treatment and any controls. The purpose of the controls and the expected change in your measurement also needs to be clearly described (5 marks).

Text Box: Insert text here
Three solutions are provided- buffer solution,DCPIP solution, and chloroplast solution. Use the three to set up three cuvettes. All solutions are measured in microlitres using micropipettes. Label the first tube C for control .in this, put 1090 microliters of the buffer, and 10 of chloroplast solution. Label the next tube DC for dark control. here, put 1040 microliters buffer solution, 50 of DCPIP, and 10 0f chloroplast solution. Label the last tube E for the experiment. Here put 1040 microliters of buffer solution, 50 of DCPIP, and 10 of chloroplast solution. Put the dark control cuvette in a dark area and leave the other 2 in the light. Observecolor changes at 0 minutes and then measure the absorbance of each solution in each cuvette using a spectrophotometer. Do the same at 2,4,6,8,10 and 12 minutes. Note the absorbance values in a table, these will be used to later plot a graph. The purpose of the controls is to guarantee that the observed changes seen in the experiment are from the introduced variables (in this case light for dark control and DCPIP for control) and not from anything else. DCPIP in oxidized form is blue while in reduced form is colorless. The expected observations, therefore, are that the mixture with the DCPIP will turn to colorless after some time in exposure to light as photosynthesis will take place and yield electrons that reduce the DCPIP. The mixture put in darkness will not undergo any color change as light is required for photosynthesis to take place.The control though exposed to light doesn’t have DCPIP so though photosynthesis takes place here, the initial green color of chloroplast solution will persist


Results

Using the data your group collected in prac 4, produce a graph of absorbance against time using Excel. Include a suitable title, labeling of the x and y axes with appropriate units, and a figure legend. Provide a figure legend/caption (in the box, below your graph) that concisely describes the graph that is shown and the experiment that underlies the measurements. A figure legend/caption does not reproduce the entire experimental procedures in detail, but rather puts the shown result into an experimental context (12 marks for graph, 6 marks for caption/legend).

Text Box: Insert figure and caption/legend here
 
Change in absorbance with increasing time in control, dark control, and experiment solutions

Results 2.

In 200 words or less, describe the trend observed in your results (4 marks).

Text Box: Insert text here
As observed in the above graph the absorbance in E, the experiment solution reduces with time until it reaches a plateau where it ceases to reduce and remains constant. the absorbance of the dark control solution remains constant the whole time. the same is observed in the absorbance of the control solution. The absorbance levels go hand in hand with the color changes observed in the three solutions.the darker the solution the higher the absorbance. This is why as the color in the experiment solution fades the absorbance reduces. The dark control undergoes no color changes hence absorbance remains high. The control has no DCPIP hence absorbance remains low the entire time

Conclusion

In one paragraph (150 words or less) provide a conclusion linking your observed trend with the functioning of the light reactions in plants. How does the amount of light receive affect the light reactions of photosynthesis? At least 2 references required (8 marks)

Text Box: Insert text here
In conclusion, photosynthetic reactions are light-dependent and involve the release of electrons which in this case aretaken in by DCPIP which is reduced in the process hence changes from blue towards colorless. This is why the graph of E slopes down as photosynthesis takes place. As the photosynthetic process continues released electrons are taken in by DCPIP hence over time the solution fades in color. The photosynthetic process continues untilit reaches a plateau once photosystem II becomes light-saturated. after this, no more color change is observed, and the graph plateaus.C has no DCPIP hence the photosynthetic process cannot be monitored, although electrons are released there is no electron acceptor. There is no color change therefore absorbance levels remain constant. DC is put in darkness without light reactions of photosynthesis cannot take place. Therefore, no color changes are observed subsequently absorbance levels remain constant
REFERENCES
Ziehe, D., Dünschede, B.andSchünemann, D (Dec 2018). "Molecular mechanism of SRP-dependent light-harvesting protein transport to the thylakoid membrane in plants". Photosynthesis Research. 138 (3): 303–313. doi:10.1007/s11120-018-0544-6. PMC 6244792. PMID 29956039.
Whitmarsh,J, and Govindjee (1999). "Chapter 2: The Basic Photosynthetic Process". Concepts in Photobiology: Photosynthesis and Photomorphogenesis. Boston: Kluwer Academic Publishers. p. 13. ISBN 978-0-7923-5519-9.

Extension

What do

Concept map of photosynthesis

Refer to the concept map on the following page to answer these questions.

  1. What is the chemical species that is transferred through the light reactions? (Box A)

Answer: chlorophyll

  • What energy-rich compound is produced by the actions of the cytochrome complex? (Box B)

Answer: ATP

  • What is the compound (Box C) used to donate electrons to the photosystems, and which gives rise to 2H+ and O2?

Answer: H2O

  • What energy is used to energize the light reactions? (Box D)

Answer: Red light

  • What is the product of the reaction that is occurring at NADP+ reductase? (Box E)

Answer: NADPH+H+

  • Provide names for structures i and ii? (0.5 mark for each correct answer)

Answer: photosystem II and photosystem I respectively

  • The electron-accepting dye, DCPIP, substitutes for which compound in your prac 4, part B experiment?

Answer: NADP+

Introduction

In one paragraph (250 words or less) provide a brief introduction to your experiment (5 marks).  Use the following description and questions and the concept map on the previous page to guide you. Provide an overview of photosynthesis by describing the purpose of the light and dark reactions.  How do the light and dark reactions contribute to photosynthesis? Describe the products and by-products of the light reactions and the general concept of the system. What part of the system does the DCPIP substitute? At least 1 reference required.

Text Box: Insert text here
Photosynthesis involves the conversion of light energy by plants to the chemical form of energy which is later used in fueling plant activities. Consists of light and dark reaction phases. In the first phase, a molecule of chlorophyll in photosystem II(P680) takes in a photon and releases an electron. The electron is forwarded to pheophytin, which subsequently forwardsthe electron to a molecule of Quinone and this starts electron flow in a chain of electron transport leading to reducing of NADP to NADPH. The gradient of energy created by the above process is utilized by ATP synthase in ATP production. The molecule of chlorophyll in photosystem II gets back the electron it lost ultimately when a molecule of water is broken down by photolysis, releasing O2. the electron freed on photosystem II enters a molecule of chlorophyll(P700) in photosystem I. The electron goes through a chain of acceptors of electrons where it releases some energy. eventually the electron is used in the reduction of NADPwith H+ into NADPH, which has a key role in the dark phase. In the dark phase, RuBisCO enzyme gets atmosphericCO2, and using the Calvin cycle utilizes the already formed NADPH, releasing 3 sugars of carbon later used in forming starch and sucrose, hence food manufacture. The process of carbon fixation leads to the production of a 3C sugar product which in turn is changed into final carbohydrates.
References
Bryant, D.A., and Frigaard N.U.(2006) “Prokaryotic photosynthesis and phototrophy illuminated.” Trends inMicrobiology 14(11):488-496 doi:10.1016/J.TIM.2006.09.001. PMID16997562
Reece, J., Urry, L., Cain, M., Wasserman, S., Minosky, P. and Jackson, R. (2011) Biology (International ed) Pearson Education.pp235, ISBN 978-0-321-73975-9

Hypothesis

In 50 words or less, state the hypothesis of the experiment.

Text Box: Insert text here
To measure the rate at which photochemical reactions occur using color changes observed in DCPIP


Methods

In one paragraph, (250 words or less) describe your experimental procedure. Include a description of the experimental treatment and any controls. The purpose of the controls and the expected change in your measurement also needs to be clearly described (5 marks).

Text Box: Insert text here
Three solutions are provided- buffer solution,DCPIP solution, and chloroplast solution. Use the three to set up three cuvettes. All solutions are measured in microlitres using micropipettes. Label the first tube C for control .in this, put 1090 microliters of the buffer, and 10 of chloroplast solution. Label the next tube DC for dark control. here, put 1040 microliters buffer solution, 50 of DCPIP, and 10 0f chloroplast solution. Label the last tube E for the experiment. Here put 1040 microliters of buffer solution, 50 of DCPIP, and 10 of chloroplast solution. Put the dark control cuvette in a dark area and leave the other 2 in the light. Observecolor changes at 0 minutes and then measure the absorbance of each solution in each cuvette using a spectrophotometer. Do the same at 2,4,6,8,10 and 12 minutes. Note the absorbance values in a table, these will be used to later plot a graph. The purpose of the controls is to guarantee that the observed changes seen in the experiment are from the introduced variables (in this case light for dark control and DCPIP for control) and not from anything else. DCPIP in oxidized form is blue while in reduced form is colorless. The expected observations, therefore, are that the mixture with the DCPIP will turn to colorless after some time in exposure to light as photosynthesis will take place and yield electrons that reduce the DCPIP. The mixture put in darkness will not undergo any color change as light is required for photosynthesis to take place.The control though exposed to light doesn’t have DCPIP so though photosynthesis takes place here, the initial green color of chloroplast solution will persist


Results

Using the data your group collected in prac 4, produce a graph of absorbance against time using Excel. Include a suitable title, labeling of the x and y axes with appropriate units, and a figure legend. Provide a figure legend/caption (in the box, below your graph) that concisely describes the graph that is shown and the experiment that underlies the measurements. A figure legend/caption does not reproduce the entire experimental procedures in detail, but rather puts the shown result into an experimental context (12 marks for graph, 6 marks for caption/legend).

Text Box: Insert figure and caption/legend here
 
Change in absorbance with increasing time in control, dark control, and experiment solutions

Results 2.

In 200 words or less, describe the trend observed in your results (4 marks).

Text Box: Insert text here
As observed in the above graph the absorbance in E, the experiment solution reduces with time until it reaches a plateau where it ceases to reduce and remains constant. the absorbance of the dark control solution remains constant the whole time. the same is observed in the absorbance of the control solution. The absorbance levels go hand in hand with the color changes observed in the three solutions.the darker the solution the higher the absorbance. This is why as the color in the experiment solution fades the absorbance reduces. The dark control undergoes no color changes hence absorbance remains high. The control has no DCPIP hence absorbance remains low the entire time

Conclusion

In one paragraph (150 words or less) provide a conclusion linking your observed trend with the functioning of the light reactions in plants. How does the amount of light receive affect the light reactions of photosynthesis? At least 2 references required (8 marks)

Text Box: Insert text here
In conclusion, photosynthetic reactions are light-dependent and involve the release of electrons which in this case aretaken in by DCPIP which is reduced in the process hence changes from blue towards colorless. This is why the graph of E slopes down as photosynthesis takes place. As the photosynthetic process continues released electrons are taken in by DCPIP hence over time the solution fades in color. The photosynthetic process continues untilit reaches a plateau once photosystem II becomes light-saturated. after this, no more color change is observed, and the graph plateaus.C has no DCPIP hence the photosynthetic process cannot be monitored, although electrons are released there is no electron acceptor. There is no color change therefore absorbance levels remain constant. DC is put in darkness without light reactions of photosynthesis cannot take place. Therefore, no color changes are observed subsequently absorbance levels remain constant
REFERENCES
Ziehe, D., Dünschede, B.andSchünemann, D (Dec 2018). "Molecular mechanism of SRP-dependent light-harvesting protein transport to the thylakoid membrane in plants". Photosynthesis Research. 138 (3): 303–313. doi:10.1007/s11120-018-0544-6. PMC 6244792. PMID 29956039.
Whitmarsh,J, and Govindjee (1999). "Chapter 2: The Basic Photosynthetic Process". Concepts in Photobiology: Photosynthesis and Photomorphogenesis. Boston: Kluwer Academic Publishers. p. 13. ISBN 978-0-7923-5519-9.

Extension

What do you think would happened to the change in absorbance of an experimental system (assume that it is the same set up as in the prac) if a compound was added to the assay which blocked the conversion of water to oxygen, and hence the introduction of electrons at photosystem II? Two sentences (50 words or less) would be enough to answer this question. (3 marks)

Text Box: Insert text here
Loss of an electron makes chlorophyll to be in a state that's oxidized. The photochemical reactions of photosynthesis can only continue if chlorophyll is in the reduced state hence interference with water molecule ultimately ceases the process therefore no significant changes in absorbance values will be observed.

you think would happened to the change in absorbance of an experimental system (assume that it is the same set up as in the prac) if a compound was added to the assay which blocked the conversion of water to oxygen, and hence the introduction of electrons at photosystem II? Two sentences (50 words or less) would be enough to answer this question. (3 marks)

Text Box: Insert text here
Loss of an electron makes chlorophyll to be in a state that's oxidized. The photochemical reactions of photosynthesis can only continue if chlorophyll is in the reduced state hence interference with water molecule ultimately ceases the process therefore no significant changes in absorbance values will be observed.

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