The process of photosynthesis has fascinated all biologists at least once when they were first introduced to it. The science behind the production of your own food by plants using some resources which are available in plentiful amounts to all the organisms but still counterproductive for others, plants stand out amongst all the other living beings. The chemical reactions (light-dependent and light-independent) involved in the photosynthesis process are a marvel of nature that is still being studied more each day by scientists across the world.
Basic questions like ‘how plants convert light energy to chemical energy’, ‘how water and carbon dioxide are magically translated to oxygen and food’, ‘how such immobile organisms (plants) manage to never run out of their energy requirements’ and many more keep the science enthusiasts on their toes wondering about the magic that plants possess!
Sadly, this curiosity is brought down to pieces when the photosynthesis process is introduced as a formal part of the school and college curriculum. The reasons are many; one of them being the tools used to teach this already-complex topic in classroom set-up. The students are left to cram the structure of the plant, leaf, plant cells, the organelle chloroplast, and its microstructures, and then the individual structural element of light and dark reactions. The introduction of pigment molecules, photosystems (PS-I and PS-II), concepts of oxidation and reduction (redox reactions), photons, and electrons start playing crazy games with the students’ minds. And this creates a worrisome situation as students are left perplexed at the end.
Since electron transport chains and pigment molecules form a vital part of the photosynthesis process, developing a deeper understanding of what goes on at the molecular level inside the plant’s chloroplasts becomes our prime goal.
For teachers explaining this topic in their classes, this article can provide real help as it highlights the blocks encountered by students and lists practical solutions to resolve them. By the end, we’ll share why a virtual lab simulation will prove useful not only for your students but also for you as an educator to deliver concepts more efficiently.
Figure: GIF from the Photosynthesis: Electron Transport Chain simulation by Labster. It is available for High School and University / College classes.
There are 3 reasons why students dread and confuse the topic of Photosynthesis: (1) Electron Transport Chain and (2) Algae Pigment Analysis. Acknowledging these blocks is the first step toward making the topic more approachable.
Photosynthesis is a complex assembly of many metabolic processes that are usually classified under the 2 stages; one light dependent (light reaction) and the other light independent (dark reaction). Specificities of the different reactions like the requirement of reducing and oxidizing agents, photons, energy carrier molecules like ATPs and NADPHs, abiotic factors like water availability, light irradiance, carbon dioxide saturation, etc demand a lot of critical thinking and introspection. Lacunae of pictorial or visual tools further amplify the fear and hesitation in students related to these intricacies.
Since chemical reactions and prerequisites of the different steps of the ETC demand different chemical entities, the topic becomes data-rich and heavy on content. The knowledge of different pigment molecules (chlorophyll types, carotenoids, xanthophylls, phycobilins, etc), ETC-important locations of plant chloroplasts (thylakoid lumen, chloroplast stroma), different wavelengths of PAR i.e. photosynthetically active radiation, spectra of pigments (absorption and action) and protein systems (PS-I and PS-II) drive the students mad. Simply cramming these details without understanding the rationale behind them can make the topic sound boring and incomprehensible.
Another major issue faced by students while studying this topic is that it sounds impractical. The complex illustrations in the books present no real-world utility to students. While students understand that the process is wondrous in nature, classroom teaching fails to exhibit any beneficial cause where theoretical knowledge can be applied.
In order to address the blocks encountered while teaching this topic, educators can engage the under-listed solutions in their classes. These can clarify many instrumental aspects of both ETC and pigment complexes. Not only can they make teaching easier for educators like you but will also make lessons clearer and easier to assimilate for your students.
Often teachers of botany, biochemistry, and plant physiology who teach this particular course ignorantly start off their class directly with sophisticated terminologies. This doesn’t even provide a chance to students to initiate visualization in their heads. Educators can take a slow and well-guided route when explaining these topics to students. We suggest some ways that can be helpful.
a. First explain the structure of the plant body (roots, stems, leaves).
b. Then explain the importance of leaves as why they are the major photosynthesizing organs of the plant body. (Reason: the presence of high amounts of photosynthetic pigments as compared to other parts)
Figure: This snippet from the Photosynthesis: Electron Transport Chain simulation by Labster helps your students to understand where exactly the pigment complex and ETC are located in the plants. It is available for High School and University / College classes
c. Then advent on to explain the structure of leaf cells and the importance of the organelle called ‘plastids’ (especially chloroplasts).
Figure: This snippet from the Photosynthesis: Electron Transport Chain simulation by Labster shows the different components of the plant cell. Identify the chloroplast in the, It is available for High School and University / College classes.
d. Discuss the structure of chloroplasts (thylakoids, thylakoid membrane, thylakoid lumen, stroma, lamella, orientation of ATP synthase, position of NADP reductase)
e. After this briefly explain why photosynthesis is important.
f. Give a brief overview of the prerequisites of the photosynthesis process (water, CO2, sunlight).
g. Now, you should take your students into the details, one at a time.
h. Explain how 2 different types of reactions are there and their individual importance.
i. how PS-II, oxygen-evolving complex, plastoquinone, cytochrome, PS-I, Fe-NADP reductase, and ATP synthase are organized in a chain called “electron transport chain”. Emphasize the importance of each of these membrane proteins and electron carriers. Take it very slowly; otherwise, this can be overwhelming for your students.
Figure: This snippet from the Photosynthesis: Electron Transport Chain simulation by Labster shows the different components of the Electron Transport Chain. Students can interact with the LabPad tool to learn more about each one of them. It is available for High School and University / College classes
j. Once the basic chain of events is clear to your students, explain the quantities. Like the number of photon molecules that incite the PS-II, the number to water molecules that split to give rise to oxygen, the number of electrons moved in the subsequent process and the number of NADPH and ATP produced.
Figure: This snippet from the Photosynthesis: Electron Transport Chain simulation by Labster shows what exactly happens at the PS-II of the ETC. The red-colored structure is the PS-II. Students can interact with the LabPad tool to learn more. It is available for High School and University / College classes
k. Explaining the directions and numbers of hydrogen ions moving across the thylakoid membrane (from stroma to thylakoid lumen and vice versa) in ETC can provide further clarity as to why NADPH and ATP are synthesized in the stroma and not in any other location of the chloroplast.
These are some of our time-tested hints for educators like you. In order to develop a good understanding amongst your students, taking this topic slowly and steadily is an earnest request and recommendation.
Teaching sessions with experiments and lively demonstrations are always a treat for the learners, especially when a topic as complex as ETC and Photosynthesis Pigment Complex is being explained. You can use the following example in your class to deliver an effective lesson on the topic of Hill’s reaction
Example: Ask your students to self-educate about the concept of PAR. As they learn that amongst the different wavelengths of sunlight, only a restricted range called PAR is utilized for photosynthesis by plants and algae alike, they’ll conceive some notions. Introduce them to the absorption and action spectrum of the general pigment molecules like chlorophyll and carotenoids. This is again bound to fixate another notion in their heads that the ETC of photosynthesis is switched on and primarily run by red and blue light.
Now begins the interesting experiment and analytical thinking session in the class…
a. Introduce them to dark-colored algae (not green-colored, therefore lack chlorophyll). And put forth a question if these algae will use red and blue light as the other green plants and algae, or will it use green light.
b. If it uses green light, is the measurement of electron flow possible using lab tools (for example using spectrophotometry)?
c. Introduce the lab technique that Dr. Robert Hill designed for in vitro measurement of electron flow in ETC. Explain the importance of the redox dye (like DCPIP) that’s used in such a lab-based experiment. Ask them to look out for any changes in the color of the dye (which signifies a change in redox state, i.e. an electron movement in the ETC).
In order to engage your students in this little experiment, you can also use the Photosynthesis: Algae Pigment Analysis simulation provided by Labster. This experiment will clear many concepts for your students like:
a. Importance of natural NADPH and artificial DCPIP
b. Pigment molecule and its specificity for PAR (Rationale: Dark algae possess different pigments for utilizing green light for photosynthesis. The energy production and electron flow are quantifiable using the change in spectrophotometer reading.)
c. Feasibility of using dark-colored algae for biofuel production (but under a different range of light, i.e. green light)
d. Concept clarity of Hill’s reaction
e. Importance of lab handling (use of ice buckets, micropipettes, spectrophotometer, different controls like positive and negative)
f. Understanding of absorption and action spectrum of different photosynthetic pigments
You can further design experiments and demonstrate more concepts like how chloroplast suspension containing pigment fraction exposed to light shows active action spectra while the same kept in dark (negative control) fails to do so. You can use the Photosynthesis: Algae Pigment Analysis simulation provided by Labster for this demonstration too.
Figure: This snippet from the Photosynthesis: Algae Pigment Analysis simulation by Labster shows lab workbench set-up for pigment fraction analysis. Students can interact with the LabPad tool to learn more. It is available for High School and University / College classes
Introduce the work of Dr. Robert Hill who elucidated the light reaction of photosynthesis with his distinguished caliber and ingenuity. In his memory and honor, the light reaction is sometimes referred to as Hill’s reaction. Stories about successful scientific endeavors might catch students' interest and motivate them to innovate in the future.
Robert Hill understood that oxygen production in photosynthesis doesn’t require CO2. He demonstrated it by using chloroplasts in vitro. He used artificial electron acceptors (a dye DCPIP). The man’s intellect made him equate DCPIP with natural NADP in the in vitro set-up. And it worked! As the chloroplast was subjected to light treatment, H2O molecules split and electron flow initiated. At last, Oz was generated and electron flow became visible by the change of the dye’s color.
Such stories can be engaging and mind-stirring. You can employ a similar storytelling technique for explaining the intricacies of the topic.
Figure: This snippet from the Photosynthesis: Algae Pigment Analysis simulation by Labster shows the use of DCPIP (Hill’s Reagent) in the in vitro experiment. Students can interact with the LabPad tool to learn more. It is available for High School and University / College classes.
Emphasize that the industrial shift from conventional sources of energy to sustainable sources is monumental in the history of mankind. Explain how this is creating a market for the biofuel industry. And then explain how this is the biggest example where the photosynthesis process is exploited at a mega-industrial level. If you understand the Basic Science behind photosynthesis, ETC, pigments, etc, you can innovate and apply your knowledge that potentially can one day make the most efficient photosynthetic machine. Such an optimized plant or algae would be able to serve as an exceptional biofuel replacing the conventional harmful fuels.
Quote similar examples to boost students to develop robust core concepts. This can ensure brilliance to perpetuate in the future STEM scientists!
Now since we very well know that the topic is full of complexities and there’s a huge void of visualization options, educators struggle to teach it. With virtual laboratory simulations from Labster, teachers can make more insightful points as students are rendered with better visual options. The 3D simulations can help you in engaging your students as the electron traverses its journey in the ETC. They can also understand the absorption and action spectra in a better way using the graphical representations of simulation.
Your students don’t have to struggle to imagine the different steps and structural components themselves as our interactive Photosynthesis: Algae Pigment Analysis and Photosynthesis: Electron Transport Chain simulations along with gamification elements come to the rescue. By using this way of active and immersive teaching, our virtual learning platform takes an advent in the field of Science to make the upcoming scientists thorough with the “basics of their respective subjects”.
You can learn more about the Photosynthesis: Algae Pigment Analysis and Photosynthesis: Electron Transport Chain simulations here or get in touch to find out how you can start using virtual labs with your students.
Figure: This snippet is from the Photosynthesis: Algae Pigment Analysis simulation by Labster. Students can interact with the LabPad tool to learn more. It is available for High School and University / College classes.
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