What is Photosynthesis?
Photosynthesis is referred to as the process of converting the light energy of the Sun into chemical energy. During this process, the light energy gets captured and is then used to convert carbon dioxide and water to glucose and oxygen.
Photosynthetic processes can be divided into two categories: oxygenic and anoxygenic. Both work on the same principles, although plants, algae, and cyanobacteria use oxygenic photosynthesis the most.
Light energy transfers electrons from water (H2O) taken up by plant roots to CO2 to make carbohydrates during oxygenic photosynthesis. The CO2 is "reduced," or gains electrons, while the water is "oxidised," or loses electrons, in this process. Along with carbs, oxygen is generated.
6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O
"Anoxygenic Photosynthetic Bacteria," anoxygenic photosynthesis uses electron donors that aren't water and don’t produce oxygen. Green sulfur bacteria and phototrophic purple bacteria are among the microorganisms that undergo this activity.
CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O
However, this entire process of photosynthesis occurs in two different processes:
Light reaction and dark reaction.
Light Reaction
The light reaction of the photosynthesis occurs in the chloroplast inside the grana. In this reaction, the light energy is converted to chemical energy in the form of ATP and NADPH. In this reaction, when phosphate is added in the presence of sunlight or by the process of ATP synthesis by cells, it is referred to as photophosphorylation. Carotenoids make up the accessory pigments. The chlorophyll in the thylakoid membrane of chloroplasts absorbs the energy from the sun. Two-electron transport chains generate ATP and NADPH, which are then transferred to ATP and NADPH. During the process, both water and oxygen are utilised.
Dark Reaction
In the dark reaction of photosynthesis, the energy which is produced in the light reaction is used for converting carbon dioxide into carbohydrates. This reaction happens in the stroma of the chloroplasts. The nighttime reactions of photosynthesis are propelled by the energy provided by ATP (made during the light reactions). The phrase "dark reactions" does not imply that the reactions take place at night or that darkness is required. It means that the reactions can continue regardless of how much light is present. The phrase is solely used to differentiate between dark and light reactions, both of which require light.
Students can refer to the Light Dependent Reactions page for more information.
What is Photophosphorylation?
Otto Kandler published the first experimental evidence for photophosphorylation in vivo in 1950, utilising intact Chlorella cells and interpreting his findings as light-dependent ATP production. With the use of P32, Daniel I. Arnon identified photophosphorylation in isolated chloroplasts in vitro in 1954. In 1956, he released his first review of early photophosphorylation studies.
Photophosphorylation is the process in which light energy is used from photosynthesis to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP). It is the process in which the energy-rich ATP molecules are synthesised by the transfer of the phosphate group to the ADP molecule during the presence of sunlight.
Photophosphorylation is of Two Different Types:
Non-cyclic photophosphorylation
Difference Between Cyclic and Non-Cyclic Photophosphorylation
Cyclic Photophosphorylation
Cyclic photophosphorylation is a process that results in the movement of the electrons in a cyclic way to synthesise the ATP molecules. In this process, the plant cells convert ADP to ATP to gain immediate energy for their cells. The process of cyclic photophosphorylation generally occurs in the thylakoid membrane and makes use of Photosystem I and Chlorophyll P700.
Non-cyclic Photophosphorylation
Non-cyclic photophosphorylation is a process that results in the movement of the electrons in a non-cyclic way to synthesise the ATP molecules by using the energy from the excited electrons that are provided by Photosystem II.
Students Can Check All Other Biology-related Topics for Their Reference-
FAQs on Difference Between Cyclic and Non-Cyclic Photophosphorylation
1. Explain the Process of Non-cyclic Photophosphorylation in Detail.
Phosphorylation refers to the process in which ATP gets formed from ADP in the light reaction of the process of photosynthesis. This process is carried out in two different ways, namely, cyclic photophosphorylation and non-cyclic photophosphorylation.
Non-cyclic photophosphorylation refers to the process in which the electrons that are expelled from the exciting photo center do not return. This process happens when both photosystems I and II are involved. The photolysis of water leads to the release of electrons and hence, a constant water supply is needed. In this process, both NADPH and ATP get formed.
2. Differentiate Between Cyclic and Noncyclic Photophosphorylation.
The differences between cyclic and noncyclic photophosphorylation include
Cyclic photophosphorylation happens only in the photosystem I but non-cyclic photophosphorylation occurs in both the photosystems I and II.
In cyclic photophosphorylation, only ATP is produced, whereas, in non-cyclic photophosphorylation, both NADPH and ATP are produced.
In cyclic photophosphorylation, the electrons get expelled by photosystem I and they return to the system. On the other hand, in non-cyclic photophosphorylation, the electrons that are expelled by the photosystems do not return.
Photolysis of water does not occur in cyclic photophosphorylation, but it occurs in non-cyclic photophosphorylation.
Oxygen does not get released in cyclic photophosphorylation, but it gets released in the case of non-cyclic photophosphorylation.
Water does not get consumed in cyclic photophosphorylation, but it gets consumed in non-cyclic photophosphorylation.
3. What is the difference between cyclic and non-cyclic photophosphorylation?
The main difference is in the electron flow: cyclic photophosphorylation involves a cyclic electron flow within Photosystem I, while non-cyclic photophosphorylation has a linear electron flow between Photosystem II and Photosystem I.
4. What is cyclic photophosphorylation?
Cyclic photophosphorylation is a process in which electrons cycle back to Photosystem I (PS-I) after generating ATP, without producing oxygen or NADPH.
5. What is non-cyclic photophosphorylation?
Non-cyclic photophosphorylation is a process where electrons move linearly from Photosystem II (PS-II) to Photosystem I (PS-I), producing ATP, NADPH, and oxygen through water photolysis.
6. Cyclic vs Non-Cyclic Photophosphorylation: Which produces oxygen?
Non-cyclic photophosphorylation produces oxygen as a byproduct of water photolysis, while cyclic photophosphorylation does not produce oxygen.
7. What are the similarities between cyclic and non-cyclic photophosphorylation?
Both processes occur in the thylakoid membrane, involve the absorption of light energy, and contribute to ATP production in photosynthesis.
8. Why is non-cyclic photophosphorylation essential for photosynthesis?
Non-cyclic photophosphorylation is essential because it generates both ATP and NADPH, which are critical for the Calvin cycle and oxygen production.
9. In which organisms do cyclic and non-cyclic photophosphorylation occur?
Cyclic photophosphorylation occurs in photosynthetic bacteria and isolated chloroplasts, while non-cyclic photophosphorylation is observed in algae, plants, and cyanobacteria.
10. What are the products of cyclic vs non-cyclic photophosphorylation?
Cyclic photophosphorylation produces only ATP, while non-cyclic photophosphorylation produces ATP, NADPH, and oxygen.
11. Does photolysis occur in cyclic photophosphorylation?
No, photolysis of water occurs only in non-cyclic photophosphorylation, leading to oxygen release and electron donation to Photosystem II.
12. Why is cyclic photophosphorylation less common than non-cyclic photophosphorylation?
Cyclic photophosphorylation is less common because it does not produce NADPH or oxygen, which are essential for the Calvin cycle and aerobic life processes.
