Talk:Photosynthesis

Semi-protected edit request on 8 March 2022

in the text there is a typo. Change the word "photosyntethic" to "photosynthetic" Mfmdec (talk) 16:06, 8 March 2022 (UTC)

Good catch, thanks.  Done  BelowTheSun  (T•C) 16:17, 8 March 2022 (UTC)

Equation not correct

We read in section "Light-independent reactions", calvin cycle: 3 CO2 + 9 ATP + 6 NADPH + 6 H+ → C3H6O3-phosphate + 9 ADP + 8 Pi + 6 NADP+ + 3 H2O

But this is not correct, it should be:

3 CO2 + 9 ATP + 6 NADPH + 6 H+ + 5 H2O → C3H6O3-phosphate + 9 ADP + 8 Pi + 6 NADP+

Not water is produced, rather needed for the hydrolysis of ATP->ADP. If you don't believe me, don't write ATP, but C10H16N5O13P3 and ADP is C10H15N5O10P2. --2A02:810D:1600:2FD0:7C48:3C9:B08C:7686 (talk) 12:50, 11 April 2022 (UTC)

oxygen "stores chemical energy"?

I find the following sentence in the lede less than helpful:

In most cases, oxygen is also released as a waste product that stores three times more chemical energy than the carbohydrates.

That sentence simply makes very little sense: chemical energy is released or stored through chemical reactions. There's no absolute way of saying that 6 O2 contains "three times more chemical energy" than glucose. All you can say is how much energy is required for the overall reaction producing those two products from CO2 and water. (The story is very different for nuclear reactions, E=mc² etc. etc.)

In fact, what the reference talks about is the bond energy of O2, that released by the reaction ${\ce {O + O -> O2}}$ of monatomic oxygen to O2. That bond energy is 498 kJ per mole of O2 produced. Great. The hypothetical reaction 6 C + 12 H + 6 O -> glucose releases, apparently, 9672 kJ per mole of glucose produced.

That doesn't mean that O₂ "contains more chemical energy" than glucose. It certainly doesn't mean that it "stores three times more chemical energy". For starters, 9672 isn't "3 times more" than 2988, it's 3.23 times as much. More importantly, again, this is the energy released by forming bonds.

Quite the reverse is true: if, hypothetically, we had an infinite supply of glucose and split it into its individual (non-bonded) atoms, the products of that reaction would store 3.23 times as much energy per mole of glucose as splitting 6 moles of oxygen into its monatomic form could store. (Which is a silly idea under standard conditions, because the monatomic oxygen would form molecules almost right away.)

So the numbers simply don't mean what the article claims they do; the "three times more" is incorrect; the reference doesn't mention any factor of 4 (or 3); the reference should be secondary for such an important statement (or at least it would be important if it made sense).

I'm removing the sentence. Feel free to revert and discuss, but as it is it's unsourced OR which misrepresents what I'm pretty sure the authors of the paper intended to say.

IpseCustos (talk) 20:35, 7 June 2022 (UTC)

Semi-protected edit request on 17 August 2022

and thats why the sky is blue Hannah blood (talk) 12:12, 17 August 2022 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. EnIRtpf09b^{chat with me}

As discussed in Diffuse_sky_radiation#Color, the explanation has nothing to do with photosynthesis, but rather that blue light is scattered more. Boghog (talk) 07:30, 18 August 2022 (UTC)

References

photosynthesis

Without photosynthesis their would be no life.During photosynthesis plants take carbon dioxide (CO2) and water (H20) from the air and soil. (By:Fatima waseem) 69.112.151.30 (talk) 14:08, 19 August 2022 (UTC)

Photosynthesis and solar panels efficiencies

Plants usually convert light into chemical energy with a photosynthetic efficiency of 3–6%. By comparison, solar panels convert light into electric energy at an efficiency of approximately 6–20% for mass-produced panels, and above 40% in laboratory devices. The 6-20% is now 20-40% and the electric energy of the panels is virtually infinite temperature while recombining hydrocarbons and oxygen at most gives a couple of thousand Kelvins. For most modern uses this corresponds to another factor of 3 in desirability of the photovoltaic power. On the other side plants can build themselves, but also use some of the energy for themselves at least until they die. Apart for personal considerations a hard to make comparison. The most striking consideration is that the average american uses as much primary energy as what's produced by photosynthesis pro capite, no wonder we are in trouble. Oscar Blauman 10:49, 1 October 2022 (UTC)