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Nikita Parmar

Updated on 02nd May, 2023 , 4 min read

Differentiate Between Cyclic and Noncyclic Photophosphorylation: Definitions, Similarities and Key Differences

Difference Between Cyclic and Noncyclic Photophosphorylation Overview

Photosynthesis is the process through which light energy is converted into chemical energy. The acquired solar energy is used to convert carbon dioxide and water into glucose and oxygen. The photosynthetic process is divided into two parts: the light reaction and the dark reaction. Photophosphorylation is the insertion of a phosphate group during the light reaction of photosynthesis in the presence of light.

What is Photophosphorylation?

Otto Kandler discovered photophosphorylation in vivo for the first time in 1950, using whole Chlorella cells, and interpreted his findings as light-dependent ATP generation. In 1954, Daniel I. Arnon used P32 to identify photophosphorylation in isolated chloroplasts in vitro. He published his first overview of early photophosphorylation experiments in 1956. Photophosphorylation is the conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) using light energy from photosynthesis (ATP). It is the mechanism by which energy-rich ATP molecules are generated in the presence of sunlight by transferring the phosphate group to the ADP molecule.

Photophosphorylation is of 2 Different Types, which are as follows-

  1. Cyclic Photophosphorylation
  2. Noncyclic Photophosphorylation

Difference Between Cyclic and Noncyclic Photophosphorylation Definitions

The following table gives definitions related to the difference between cyclic and noncyclic photophosphorylation-

Cyclic Photophosphorylation

Noncyclic Photophosphorylation

Cyclic Photophosphorylation is the mechanism by which ADP is converted into ATP to create energy for the cells' immediate needs.

Noncyclic photophosphorylation is a mechanism that harnesses the energy from excited electrons created by Photosystem II to cause non-cyclic electron movement, which results in the formation of ATP molecules.

In cyclic photophosphorylation, only one photosystem (PS I) is employed, and there is no reduction in NADP+.

The protons (H+) are formed when water molecules split and interact with electrons to reduce NADP to NADPH. The following equation depicts the reaction.

NADPᐩ+ 2Hᐩ+ 2e⁻→ NADPH + Hᐩ

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Differentiate Between Cyclic and Noncyclic Photophosphorylation

The following table gives the difference between cyclic and noncyclic photophosphorylation-

Parameters

Cyclic Photophosphorylation

Noncyclic Photophosphorylation

Meaning

The process of producing ATP during the cyclic electron transport chain of light-dependent photosynthesis is referred to as "cyclic photophosphorylation."

Noncyclic photophosphorylation is the method by which ATP is produced from the noncyclic electron transport chain in photosynthetic light reactions.

Photosynthesis Found 

Anaerobic condition

Aerobic condition

Photosystem

PS-I

PS-II

Product

ATP

Reduced coenzymes and ATP

Oxygen Production

Yes

No

Occurrence

Photosynthetic bacteria and isolated chloroplast

Algae, cyanobacteria, plants, etc.

Electron Acceptor

P700

NADP+

Flow Pattern of Electrons

Cyclic

Linear

Electron donor

P700

P680

Photolysis of water

Water does not split during this process

Water splits or photolyzes

Carbon dioxide involvement

Occurs when the CO2 concentration is less in the atmosphere

Occurs at normal CO2 concentration

Effect of Diuron 

The process is not inhibited by diuron

The process is sensitive to the diuron

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Difference Between Cyclic and Noncyclic Photophosphorylation Similarities

The following are some of the similarities between cyclic and noncyclic photophosphorylation-

  1. The light-dependent photosynthetic process includes both cyclic and noncyclic photophosphorylation.
  2. Cyclic and noncyclic photophosphorylation mechanisms are components of ETS that perform phosphorylation (phosphate group addition) or ATP production.

Key Differences Between Cyclic and Noncyclic Photophosphorylation 

The following are the distinctions between cyclic and noncyclic photophosphorylation-

  1. Cyclic photophosphorylation occurs solely in photosystem I, whereas noncyclic photophosphorylation occurs in both photosystems I and II.
  2. Only ATP is created during cyclic photophosphorylation, but both NADPH and ATP are produced during non-cyclic photophosphorylation.
  3. Electrons are evacuated by photosystem I and returned to the system during cyclic photophosphorylation. Non-cyclic photophosphorylation, on the other hand, does not return the electrons released by the photosystems.
  4. Water photolysis occurs in non-cyclic photophosphorylation but not in cyclic photophosphorylation.
  5. Oxygen is not released during cyclic photophosphorylation, but it is released during non-cyclic photophosphorylation.
  6. Although water is not used during cyclic photophosphorylation, it is consumed during non-cyclic photophosphorylation.

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Sample Questions on Differentiate Between Cyclic and Noncylic Photophosphorylation

Sample Question 1: Define the term "photophosphorylation."

Photophosphorylation is the insertion of a phosphate group during the light reaction of photosynthesis in the presence of light. Photophosphorylation is phosphorylation that takes place in the presence of light.

Sample Question 2: What are the two different forms of photophosphorylation?

Ans: Photophosphorylation is classified into two types: cyclic photophosphorylation and non-cyclic photophosphorylation.

Sample Question 3: Describe the non-cyclic photophosphorylation mechanism.

When electrons are liberated from the excited photo center and do not return, the process of non-cyclic photophosphorylation occurs. Only when both photosystems I and II are involved does this process occur. Water photolysis results in the release of electrons. As a result, a consistent supply of water is necessary for this operation. During this process, both NADPH and ATP are produced.

Sample Question 4: Which of the following scenarios is optimal for cyclic photophosphorylation?

The cyclic photophosphorylation approach is only suitable for bacteria.

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Things to Remember

  1. The two processes of photosynthesis are the light reaction and the dark reaction. The dark response occurs in the absence of light, whereas the light reaction occurs in the presence of light.
  2. The photosynthetic light reaction occurs in the grana's chloroplast.
  3. In the photosynthetic light process, light energy is converted into chemical energy in the form of ATP and NADPH.
  4. In the dark reaction of photosynthesis, the energy provided by the light reaction is used to transform carbon dioxide into carbohydrates. This occurs within the chloroplast stroma.
  5. Photophosphorylation is the insertion of a phosphate group during the light reaction of photosynthesis in the presence of light.
  6. Photophosphorylation is phosphorylation that takes place in the presence of light.
  7. Electrons in cyclic photophosphorylation move in a cyclic pattern, whereas electrons in non-cyclic photophosphorylation do not travel in a cyclic pattern.

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Frequently Asked Questions

Ans. Proton Motive Force is the other main source of energy in photophosphorylation.

Ans. Cyclic photosynthesis generates ATP but not NADPH.

Ans. Phosphorylation is the mechanism by which ATP is produced from ADP during the light response of photosynthesis. This process can be carried out in two ways: cyclic photophosphorylation and non-cyclic photophosphorylation. The process in which electrons are released from the exciting photo center and do not return is referred to as non-cyclic photophosphorylation. When both photosystems I and II are involved, this process occurs. Because the photolysis of water results in the release of electrons, a steady supply of water is required. Both NADPH and ATP are generated during this process.

Ans. Cyclic flow of pattern in the cyclic and linear flow of pattern in noncyclic photophosphorylation.

Ans. The following equation depicts the reaction: NADPᐩ+ 2Hᐩ+ 2e⁻→ NADPH + Hᐩ

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