Explain the processes that take place in the stroma including the reactants going in and the products produced from these processes in (a) bright sunlight and in (b) darkness. (c) What happens over an extended period of darkness of many days?
please help, i tried re reading the information that went over this but i am having a hard time understanding please help, thx!<3
They are the light reactions and calvin cycle. The products from light reactions are ATP and NADPH.
Sure, I'd be happy to help explain the processes that take place in the stroma and the differences between bright sunlight and darkness.
The stroma is the fluid-filled space inside the chloroplasts, which are organelles found in plant cells. It is where several important processes occur, including the Calvin cycle, which is responsible for carbon fixation and the production of glucose.
(a) In bright sunlight:
During bright sunlight, photosynthesis occurs at its maximum capacity. The stroma receives energy in the form of sunlight, which is absorbed by the chlorophyll pigments in the thylakoid membranes. The absorbed light energy is then used in the light-dependent reactions that take place in the thylakoid membranes. These reactions produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are energy-rich molecules that will be used in the Calvin cycle.
Once the ATP and NADPH are produced in the thylakoid membranes, they move into the stroma to participate in the Calvin cycle. The Calvin cycle takes carbon dioxide (CO2) from the atmosphere as its starting reactant, along with the ATP and NADPH produced in the light-dependent reactions. In the stroma, the CO2 is converted into glucose through a series of chemical reactions. Glucose is a sugar molecule that serves as an energy source for the plant.
Therefore, in bright sunlight, the reactants entering the stroma are CO2, ATP, and NADPH, while the product produced is glucose.
(b) In darkness:
In the absence of light, or during darkness, the light-dependent reactions cannot occur, as they rely on light energy. As a result, there is no production of ATP or NADPH. Without ATP and NADPH, the Calvin cycle cannot proceed since it requires these energy-rich molecules as a source of energy.
In darkness, the reactant CO2 is not efficiently converted into glucose because the Calvin cycle is limited by the absence of ATP and NADPH. Instead, plants may switch to alternative metabolic processes, such as respiration, where glucose is broken down to release energy.
(c) Over an extended period of darkness (many days):
When a plant is subjected to extended periods of darkness, it ultimately affects its overall growth and survival. Without sufficient light, the plant's energy reserves, stored as carbohydrates (such as glucose), will gradually be utilized. Initially, the plant consumes the readily available glucose stored in its cells. As these reserves deplete, the plant may then rely on other energy sources or enter a state of dormancy. Continued darkness can result in the depletion of energy reserves and, ultimately, the plant's death if it is unable to access sufficient light for extended periods.
I hope this explanation clarifies the processes that take place in the stroma and the differences between bright sunlight and darkness. Let me know if you have any further questions!