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This transport chain produces a proton-motive force, pumping H + ions across the membrane and producing a concentration gradient that can be used to power ATP synthase during chemiosmosis. This pathway is known as cyclic photophosphorylation, and it produces neither O 2 nor NADPH.
It has two components: a difference in proton concentration (a H + gradient, ΔpH) and a difference in electric potential, with the N-side having a negative charge. [ 4 ] ATP synthase releases this stored energy by completing the circuit and allowing protons to flow down the electrochemical gradient, back to the N-side of the membrane. [ 5 ]
Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient.An important example is the formation of adenosine triphosphate (ATP) by the movement of hydrogen ions (H +) across a membrane during cellular respiration or photosynthesis.
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
According to the hypothesis, the high concentration of organic substances, particularly sugar, inside the phloem at a source such as a leaf creates a diffusion gradient (osmotic gradient) that draws water into the cells from the adjacent xylem. This creates turgor pressure, also called hydrostatic pressure, in the phloem. The hypothesis states ...
In contrast, C3 plants directly perform the Calvin Cycle in mesophyll cells, without making use of a CO 2 concentration method. Malate, the four-carbon compound is the namesake of "C4" photosynthesis. This pathway allows C4 photosynthesis to efficiently shuttle CO 2 to the RuBisCO enzyme and maintain high concentrations of CO 2 within bundle ...
Phosphoglycolate is quickly metabolized to glycolate that is toxic to a plant at a high concentration; it inhibits photosynthesis. Salvaging glycolate is an energetically expensive process that uses the glycolate pathway, and only 75% of the carbon is returned to the Calvin-Benson cycle as 3-phosphoglycerate.
Although, a nutrient concentration gradient would result from longitudinally uniform concentrations and flows, the complicated flow trajectories predicted produce a larger concentration gradient across the vacuolar membrane. [8] By Fick's laws of diffusion, it is known that larger concentration gradients lead to larger diffusive flows. [13]