H+ concentration gradient Photosynthesis

In summary, the textbook says that the H+ concentration gradient across the thylakoid membrane is maintained by: 1) photolysis 2) transport of electrons from photosystem II along carriers 3) formation of NADPH.
  • #1
garytse86
311
0
FOr the light dependent reaction, In the textbook it says that the H+ concentration gradient across the thylakoid membrane is maintained by:

1) photolysis
2) transport of electrons from photosystem II along carriers
3) formation of NADPH.

I can understand 1) and 3), but I have no idea how transport of e- would maintain a hydrogen ion concentration gradient. Can someone help please?

THanks.

Gary
 
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  • #2
Does this statement help:

The cytochrome b6/f complex acts to pump H+ across the thylakoid during electron transport
 
  • #3
so this is exactly the same as cyclic phosphorylation then? energy from e- is used to pump H+ across thylakoid membrane?
 
  • #4
but it seems silly for plants to have evolved such mechanisms.
Why pump the hydrogen into the lumen, and when they diffuse out along the electrochemical gradient the energy is used to synthesise ATP. Why go through this process, why can't the energy just be used to synthesise ATP in the first place?
 
  • #5
Energy for e- is used to pump H+ out. ATP is synthesis due to that process, which is why H+ are pump out.

Look at the figure
http://bio.winona.msus.edu/bates/Bio241/images/figure-08-12-1.jpg
 
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  • #6
why go through H+? why can't the energy from the electrons be directly used to synthesise ATP?
 
  • #7
There is no mechanism to do it directly. ATP synthase is powered by the proton gradient. The only way to make ATP is to use the enzyme ATP synthase, because of the structure of the ATP. Energy has to be transferred from photons to electrons to the H+ gradient, then to ATP.
 
  • #8
nipwoni said:
There is no mechanism to do it directly. ATP synthase is powered by the proton gradient. The only way to make ATP is to use the enzyme ATP synthase, because of the structure of the ATP. Energy has to be transferred from photons to electrons to the H+ gradient, then to ATP.
oh now i get it. It is because of the structure of the enzyme which needs a H+ gradient.


Many thanks to all of you.

Gary
 

Related to H+ concentration gradient Photosynthesis

1. What is an H+ concentration gradient in photosynthesis?

The H+ concentration gradient in photosynthesis refers to the difference in concentration of hydrogen ions (H+) between the thylakoid lumen (inside of the thylakoid) and the stroma (fluid-filled space outside of the thylakoid). This gradient is created during the light-dependent reactions of photosynthesis and is essential for the production of ATP and NADPH, which are used in the light-independent reactions.

2. How is the H+ concentration gradient created in photosynthesis?

The H+ concentration gradient is created through the process of chemiosmosis. During the light-dependent reactions, energy from sunlight is used to pump H+ ions from the stroma into the thylakoid lumen, creating a higher concentration of H+ ions inside the thylakoid. This creates an electrochemical gradient, with a higher concentration of positive ions inside the thylakoid.

3. Why is the H+ concentration gradient important in photosynthesis?

The H+ concentration gradient is important because it is used to produce ATP, the energy currency of the cell. As H+ ions flow back out of the thylakoid lumen through ATP synthase, the energy released is used to convert ADP into ATP. This process, known as chemiosmosis, is essential for the light-dependent reactions of photosynthesis and the overall production of glucose.

4. How does the H+ concentration gradient affect the rate of photosynthesis?

The H+ concentration gradient is closely linked to the rate of photosynthesis. The greater the difference in H+ concentration between the thylakoid lumen and the stroma, the more energy can be produced and the faster the rate of photosynthesis. Additionally, the H+ concentration gradient is responsible for the production of NADPH, which is also essential for the light-independent reactions and the overall rate of photosynthesis.

5. Can the H+ concentration gradient be disrupted in photosynthesis?

Yes, the H+ concentration gradient can be disrupted by various factors such as changes in pH, temperature, or the availability of certain molecules. This can affect the rate of photosynthesis and ultimately the overall production of glucose. For example, if the thylakoid membrane is damaged, the H+ concentration gradient may be disrupted and the production of ATP and NADPH will be affected.

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