Difference between Cyclic and Noncyclic Photophosphorylation – Comparison Table

compare cyclic and noncyclic photophosphorylation

Cyclic Photophosphorylation vs Non-cyclic Photophosphorylation
(Similarities and Differences between Cyclic and Non-cyclic Photophosphorylation)

The process of photosynthesis is completed in two main steps – Light reaction and Dark reaction. The Light reaction is the light-dependent reaction where the assimilatory powers (ATP and reduced coenzymes) are generated in the grana of chloroplasts. During the light reaction, photolysis of water and evolution of oxygen take place. In the dark reaction (light independent reaction), the assimilatory powers synthesized in the light reaction are utilized to reduce the CO2 to carbohydrates.

During the light reaction, energy in the sunlight is captured by the reaction centers of photosystems (PS I and/or PS II) and they expel electrons with high energy. These electrons then pass through a series of complexes called Electron Transport System (ETS) to synthesize the assimilatory powers. During the pathway of electrons through the ETS, phosphorylation reaction occurs at specific points which results in the synthesis of energy-rich APT molecules. Since this phosphorylation is occurring in presence of light, it is called photophosphorylation. Depending upon the path of electrons in the electron-transport-system of the primary photochemical reaction, there are two types of photophosphorylation processes. They are (1) Cyclic photophosphorylation and (2) Noncyclic photophosphorylation. The present post discusses the similarities and differences between cyclic and noncyclic photophosphorylation with a comparison table.

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Difference between Mesophyll and Bundle Sheath Cells and Chloroplasts in C4 Plants

chloroplast variation of C4 plants

Differences between Mesophyll and Bundle Sheath Cells and Chloroplasts in C4 Plants
Mesophyll vs Bundle Sheath Chloroplasts: A Comparison Table)

The C4 cycle or Hatch and Slack pathway of dark reaction of photosynthesis are characterized by two structurally and functionally different chloroplasts in their leaves. The leaves of C4 plants such as maize possess the classical Kranz anatomy. In Kranz anatomy, each vascular bundle is surrounded by a ring of bundle sheath cells, followed by one or more concentric layers of mesophyll cells. Bundle sheath cells have thick cell walls and contain centrifugally arranged chloroplasts with large starch granules and unstacked thylakoid membranes, whereas the mesophyll cells contain randomly arranged chloroplasts with stacked thylakoids and little or no starch grains.

The mesophyll chloroplasts in C4 plants are highly specialized to do the light dependent reactions of photosynthesis whereas the bundle sheath cells are specialized to perform the light independent reactions. In C4 cycle, the atmospheric CO2 is first accepted by PEP in the cytoplasm of the mesophyll cells and converted to OAA with the help of the enzyme PEP carboxylase. OAA is then transported from the mesophyll cells to the bundle sheath cells. In the bundle sheath cells, OAA releases molecular CO2 and which is accepted by the regular RuBP to run the Calvin cycle or C3 cycle for the synthesis of carbohydrate precursors. 

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