What happens if the thylakoid membrane is permeable to hydrogen ions?
What happens if the thylakoid membrane is permeable to hydrogen ions?
If the thylakoid membrane was highly permeable to hydrogen ions, then the electron transfer chain would not be able to produce a hydrogen ion gradient across the membrane. Hydrogen ions would not flow through ATP synthase, and ATP synthesis would cease. ATP is generated in the process.
Is the thylakoid membrane permeable to protons?
At various stages in this process, protons are released into the thylakoid lumen or taken up from the stroma, generating a proton gradient. Such a gradient can be maintained because the thylakoid membrane is essentially impermeable to protons. The thylakoid space becomes markedly acidic, with the pH approaching 4.
What would happen if the thylakoid membrane was permeable to protons?
If the thylakoid plant membrane was readily permeable to protons, ATP synthesis would be decreased in the thylakoid.
Is the thylakoid membrane permeable to hydrogen ions?
The hydrogen ions are allowed to pass through the thylakoid membrane through an embedded protein complex called ATP synthase. The flow of hydrogen ions through ATP synthase is called chemiosmosis, because the ions move from an area of high to low concentration through a semi-permeable structure.
How does NADP become NADPH?
Photosynthesis uses a different energy carrier, NADPH, but it functions in a comparable way. The lower energy form, NADP+, picks up a high energy electron and a proton and is converted to NADPH. When NADPH gives up its electron, it is converted back to NADP+.
Why is pH of thylakoid lower than stroma?
The electron transport chain moves protons across the thylakoid membrane into the lumen (the space inside the thylakoid disk). Note that a high concentration of protons = an acidic pH, so the thylakoid lumen has a much more acidic (lower) pH than the stroma.
What are the two types of photophosphorylation?
Photophosphorylation is of two types:
- Cyclic Photophosphorylation.
- Non-cyclic Photophosphorylation.
What is the difference between cyclic and noncyclic photophosphorylation?
In the cyclic photophosphorylation, only ATP is produced, whereas, in the non-cyclic photophosphorylation both NADPH and ATP are produced. On the other hand, in non-cyclic photophosphorylation, the electrons that are expelled by the photosystems do not return.
What is the pH of stroma?
It has long been accepted that the cytoplasm and the chloroplast stroma have a neutral pH close to 7, but upon illumination the stroma is alkalized up to pH 8 as a consequence of H+-pumping into the thylakoid lumen.
How are electrons produced in the thylakoid reaction?
This reaction produces electrons that are needed for the electron transport chains, protons that are pumped into the lumen to produce a proton gradient, and oxygen. Although oxygen is needed for cellular respiration, the gas produced by this reaction is returned to the atmosphere.
How are pigments embedded in the thylakoid membrane?
Photosynthetic pigments (e.g., chlorophyll) are embedded into the thylakoid membrane, making it the site of the light-dependent reactions in photosynthesis. The stacked coil shape of the grana gives the chloroplast a high surface area to volume ratio, aiding the efficiency of photosynthesis.
When does thylakoid proton permeability increase after flash?
However, any increase in thylakoid proton permeability not associated with chloroplast ATP synthase activity increases the rate of decay of the flash‐induced electrochromic shift. Therefore, traces were analysed from 50 to 100 ms after the actinic flash, a time frame during which the fast decay dominates.
How does the chemiosmotic potential of the thylakoid membrane work?
Together, these proteins make use of light energy to drive electron transport chains that generate a chemiosmotic potential across the thylakoid membrane and NADPH, a product of the terminal redox reaction. The ATP synthase uses the chemiosmotic potential to make ATP during photophosphorylation .