Yes, I went on and became a medical doctor. I came back here anyways because I am amazed every day that light is actually the source of all energy on earth.
Wow. Thank you so much Sal. Photosynthesis is easy in general bio but in AP we get all specific and i swear i was lost. Ive been watching all your videos on photosynthesis and i feel much better on my understanding on photosynthesis. Im actually interested in learning about it and im fascinated. Your videos are SO MUCH BETTER than books/teachers. Thank you so much.
I would love to meet you in real life to give you a hug. I remember watching you on a local channel explaining what you do in your videos. My father reminded me to check youtube to help me when real people cannot and you have worked wonders. Thank you so much and please don't stop teaching!
Step 1: Don't go to lectures Step 2: Make notes from slides that prof posts online Step 3: Watch these youtube videos day before the exam Step 4: Get 93% on the exam WINNING.
Crazy how free youtube videos explain the concepts outlined in $100 textbooks better than the professors I pay tens of thousands per semester. College is a scam.
khan academy......you are the most amazing people.....you have such a good way of explaining things where lecturers talk all complex and it gets really confusing....i really admire what you do and i think i speak for everybody when i say THANK YOU SO MUCH KHAN ACADEMY
i pay 600 dollars for a class which the prof reads off the ppt for 3 hours every week. I go on khan academy and get the same content for free and in less time gotta love university
Correct me if I'm wrong but I don't think there is involvement of Photosystem 2 in cyclic photophosphorylation. Electrons flow from plastoquinone to cyt b/f to plastocyanin, then reduce ferredoxin through light driven PS1.
Both photosystem 1 and 2 push electrons through cyt b6/f. The Cyt b6/f complex is what generates the H+ Gradient. The only difference is that In noncyclic phosphorylation the Electrons come from water(oxidizing it to O2), through Photosystem 2, then through CytB6/f, then through Photosystem 1, and ultimately it ends up in NADPH. In Cyclic phosphorylation, the electrons come from photosystem 1 and NEED to be returned to photosystem 1. PS1 takes energized electrons and pushes them through the Cyt complex and then it is returned to PS1 to be re-energized(by photons).
The hydrogens are pumped from the stroma into the lumen using the energy in the electrons. When the electrons are in PS1, they are energized by photons. The energized electons get passed to Cyt B. As the electrons go through the Cyt complex it powers the hydrogen pump. As the electrons leave Cyt B they are placed back into PS1 as low energy electrons. Protons are also generated from the oxidation of water in noncyclic phosphorylation. It's very complicated what happens inside of the Cyt complex. (They call it a COMPLEX for a reason! lol) The hydrogens come from the stroma and are pumped into the lumen. Once the gradient is formed it powers ATP synthase. ATP synthase only works when Protons are being pumped back into the stroma.
You're welcome! And actually, random protons dont just float around in solution for 2 reasons. 1. The protons are bound to water, H+ is just shorthand for saying H3O+. But thats just symantics. :) And reason 2 is that they arent really random protons. They have to come from somewhere. This means that there is another molecule in your body that is missing a hydrogen and is now negatively charged. This usually has to do with the fact that water will deprotonate carboxylic acids in your body. So, pyruvate, oxolate, succinate, anything ending in ATE used to have a proton attached to it but since it is in contact with water, the water grabs it(forming the H3O+ I mentioned) and creating a carboxylate ion. You're right though. There are alot of things that I feel like teachers dont go over that can drastically help in understanding concepts. Part of this might just be because it isn't within the scope of that class to teach that type of information. Like i was watching this video while taking my plant biology course. I understood it moderately. One semester later after taking my senior level Biochemistry course I understand this whole mechanism 100x better because I know what is ACTUALLY happening in all of the complexes and not just a general flow of what is happening.
Correction: 16:54 - 17:11 The cyclic electron flow uses PSI but not PSII... The e- cyclic back from Fd to cytochrome complex from there to P700 in the PSI.
Thank you so much Sir, with out your video i would have never understood this. it was so confusing, but now i have a very good understanding. Thanks for getting into the "weeds" because it only helped me more in understanding the process..
@Sonictriforce Your statement is correct, although you fail to notice that he is talking about Linear Light Reactions, not Cyclic. In the previous video see 13:55.
im not sure if the electrons come back to the PS II in cyclic photophosphorylation. aren't they getting excited in the PS I and then returning to the PS I?
@grayshorts You're right. In cyclic photo phosphorylation, the electron skips PS2 and gets circulated back to PS1 by re-entering either the cytochrome complex or plastoquinone. Also, I thought the last electron carrier in non-cyclic is ferradoxin, not plastocyanin. Correct me if I'm wrong.
Right after protein Fd (Ferredoxin), there's a NADP+ reductase protein where NADP+ + H+ (proton) helps make NADPH ultimately for use of Calvin Cycle. Also, for cyclic photophosphorylation or cyclic electron flow, the proteins involved for the electron transport chain is PS I, Ferredoxin, Cytochrome complex, and Plastocyanin, then back to PS I. I don't think the electron transport chain goes as far back as PS II? We're only concerned about Chorophyll a (P700) in PS I when we're on Cyclic electron flow. Yes, ATP is the product of cyclic electron flow and no NADPH. Thank you for the upload! Glad to review this.
Great video , understood it fully but are unsure when you say at 16:43 that the electron return to ps11 I think it returns back to ps1 when it's in a lower energy state ? Thanks
I love that I can watch this now and make corrections ... @13:10 is all wrong. Cytochrome is missing & then its waaaay more complicated than that just 'pumping' H+
I'm as excited as these electrons hit by photons for my exam tomorrow including photosynthesis krebs cycle nitrogen cycle and eveery knowledge you can ever find in the thickest bio books Yay
I have a question , in lumen why water oxidized to form oxygen and protons while water is a highly stable molecule. In other words which force cause water to get oxidized ?? Answer me plzz
Can someone remind me what the main difference is between how ATP is produced by oxidative phosphorylation in respiration, and how it is produced in photosynthesis?
I was under the impression that it is the membrane-bound Fo portion of ATP synthase that spins to release H+ ions back into the stroma. I believe that the F1 portion (in the stroma) was held in place by a separate rigid membrane-bound structure.
ohhhhh... missed that.. XD thanks.. so basically the electron passing through the transfer chain "merger" with one of the H+ in the stroma and then bond to the NADP+ creating NADPH.... right??
I hope I'm not too late: There are actually hydrogens being used in the production of NADPH. The hydrogens used in the NADP+ are in a kind of a cycle, they're being recycled so to speak. They are already in the STROMA, so the NADP+, the e- and the H+ become NADPH with the NADP reductase. Hope this helps. Ask if you didn't understand. ^__^
This comment was 10 yrs ago, hope you're doing well! If I may ask, what do you mean by "the hydrogens are in a kind of *cycle* "? Aren't they just floating around the stroma, going with the flow of the concentration gradient?
Correct me if I'm wrong but I believe that cyclic photophosphorlylation does NOT use Photosystem 2, only Photosystem 1. At 16:50 you draw the electron going back to PS2, but it should go back to PS1. Otherwise, great lecture.
Hi there, I have a slight doubt. We have told that in both photosistems, photons doesn't excite straightly the chlorophyll a but it is picked by some other pigments or antennas on the outside of the photosistems and then the energy of the photon passes through these complexes of molecules and finally reaches the chlorophyll a in the centre of the photosistems. We have also told that the energy of the photons is transferred from the other pigments to chlorophyll a thanks to resonance energy. Here is my doubt: how does this resonance energy actually work? He said we can immagine it as a vibration but i still have doubts about how actually the resonance occurs. Like so much these videos by the way, great work.
okay so when the hydrogens are taken off of H20, are those hydrogens already in the lumen or are they in the stroma? if they are already in the lumen, where are the hydrogens in the stroma coming from?
someone confused the dislike button with the like button but dont worry, every one can make a mistake, except for the guy who does this videos he is always right
@Sonictriforce Excuse my ignorance, and I'm sorry if I'm wrong, but my textbook says exactly what the person says in the video. It's a high school textbook so I maybe the authors were trying to make it less complicated for us, but it says so nevertheless. Again, I'm sorry if I'm wrong :)
i dont understand the part with NADP+ becoming NADPH.. how does the electron make a H?? if it was NADPH+, then it wud make sense... help anyone? but its a superly awesome video...
@luisdemasiado Well, sure he's completely right with most of the stuff, but yes, when it comes to cyclic photo phosphorylation, the electron is transferred only in PS1 in a cyclic manner and doesn't even tough PS2 cuz plastocyanin transfers the electron to P700, which further transfers it to FRS, then to ferredoxin, to cyt b6, then to cyt f, back to plastocyanin and again to P700... and this cycle keeps going on, but P680 has absolutely nothing to do with cyclic photo phosphorylation.
@torresisbeast1 I did pass my test, but my teacher made the test extra hard on purpose (he told us). He started asking all of these application questions that no-one understood. I got all the fact-based things right though (things like 'How are the lost electrons replaced after they are used in Photosystem II?). On top of that, my test was also on Cellular Respiration so it's double trouble lol.
+Jonathon Shafer Photons are electromagnetic radiations or packets of light. These are mass less. Consider them like subatomic particles though they are not but size wise. Radiations don't need penetrating.
2 dislikes are from people who took the time to watch the videos, didn't take the time to even listen to what he was saying and went into their exam thinking they were a pro. oh btw they failed miserably
Lol, he is so funny!! The photons coming form 93 million miles away!! I'm just wondering if the correction is made? I don't want to learn the wrong thing or else it's hard to take the wrong info out o fmy head~.~ anyways! This is awesome!! Saves my life!!!!!!
I hope those who watched about 7,8,9 and 10 years ago passed well and are
doing well in their lives.
Yes, I went on and became a medical doctor. I came back here anyways because I am amazed every day that light is actually the source of all energy on earth.
Wow. Thank you so much Sal. Photosynthesis is easy in general bio but in AP we get all specific and i swear i was lost. Ive been watching all your videos on photosynthesis and i feel much better on my understanding on photosynthesis. Im actually interested in learning about it and im fascinated. Your videos are SO MUCH BETTER than books/teachers. Thank you so much.
I would love to meet you in real life to give you a hug. I remember watching you on a local channel explaining what you do in your videos. My father reminded me to check youtube to help me when real people cannot and you have worked wonders. Thank you so much and please don't stop teaching!
why do i find this so funny
it's so cool to see someone who is so passionate and excited about what he's explaining
Those who have disliked are professors who are jelly.
my exam is tomorrow and ive been watching your videos and theyve helped me understand cellular respiration and photosynthesis a ton more
How was the exam?
This dude right here gets excited.
God bless u khanaacademy
greets from a medical student from Kosovo
Step 1: Don't go to lectures
Step 2: Make notes from slides that prof posts online
Step 3: Watch these youtube videos day before the exam
Step 4: Get 93% on the exam
WINNING.
same here bro
you do this in uni? im doing this in grade 12 bruh
X DeHaan Solo X I'm watching this at 9th grade bro.
+Debashish Choudhury same
+Debashish Choudhury i'm in kindergarden watching this, I plan on having my bachelor's by 9th grade
I'm watching this while in my mother's womb right now. Got 120% on the last exam.
Crazy how free youtube videos explain the concepts outlined in $100 textbooks better than the professors I pay tens of thousands per semester. College is a scam.
khan academy......you are the most amazing people.....you have such a good way of explaining things where lecturers talk all complex and it gets really confusing....i really admire what you do and i think i speak for everybody when i say THANK YOU SO MUCH KHAN ACADEMY
He is better than my Bio teacher.
Yeah, you could say that we all had worst bio teachers
Bryan Nguyen true. my bio teacher literally shows us powerpoints and no talking at all.
i pay 600 dollars for a class which the prof reads off the ppt for 3 hours every week. I go on khan academy and get the same content for free and in less time
gotta love university
I have a biochem 2 exam in 10 hours. This is helping a lot.
I whitelisted your youtube channel on my AdBlock because you're a truly good man
Please never stop teaching these videos help so much
i've been growing dependent on your videos sal, thanks alot!
Correct me if I'm wrong but I don't think there is involvement of Photosystem 2 in cyclic photophosphorylation. Electrons flow from plastoquinone to cyt b/f to plastocyanin, then reduce ferredoxin through light driven PS1.
That's how I was taught.
Both photosystem 1 and 2 push electrons through cyt b6/f. The Cyt b6/f complex is what generates the H+ Gradient. The only difference is that In noncyclic phosphorylation the Electrons come from water(oxidizing it to O2), through Photosystem 2, then through CytB6/f, then through Photosystem 1, and ultimately it ends up in NADPH. In Cyclic phosphorylation, the electrons come from photosystem 1 and NEED to be returned to photosystem 1. PS1 takes energized electrons and pushes them through the Cyt complex and then it is returned to PS1 to be re-energized(by photons).
The hydrogens are pumped from the stroma into the lumen using the energy in the electrons. When the electrons are in PS1, they are energized by photons. The energized electons get passed to Cyt B. As the electrons go through the Cyt complex it powers the hydrogen pump. As the electrons leave Cyt B they are placed back into PS1 as low energy electrons. Protons are also generated from the oxidation of water in noncyclic phosphorylation. It's very complicated what happens inside of the Cyt complex. (They call it a COMPLEX for a reason! lol)
The hydrogens come from the stroma and are pumped into the lumen. Once the gradient is formed it powers ATP synthase. ATP synthase only works when Protons are being pumped back into the stroma.
You're welcome! And actually, random protons dont just float around in solution for 2 reasons. 1. The protons are bound to water, H+ is just shorthand for saying H3O+. But thats just symantics. :) And reason 2 is that they arent really random protons. They have to come from somewhere. This means that there is another molecule in your body that is missing a hydrogen and is now negatively charged. This usually has to do with the fact that water will deprotonate carboxylic acids in your body. So, pyruvate, oxolate, succinate, anything ending in ATE used to have a proton attached to it but since it is in contact with water, the water grabs it(forming the H3O+ I mentioned) and creating a carboxylate ion.
You're right though. There are alot of things that I feel like teachers dont go over that can drastically help in understanding concepts. Part of this might just be because it isn't within the scope of that class to teach that type of information. Like i was watching this video while taking my plant biology course. I understood it moderately. One semester later after taking my senior level Biochemistry course I understand this whole mechanism 100x better because I know what is ACTUALLY happening in all of the complexes and not just a general flow of what is happening.
Good to know!
Correction: 16:54 - 17:11
The cyclic electron flow uses PSI but not PSII... The e- cyclic back from Fd to cytochrome complex from there to P700 in the PSI.
Thank you so much Sir, with out your video i would have never understood this. it was so confusing, but now i have a very good understanding. Thanks for getting into the "weeds" because it only helped me more in understanding the process..
god bless khan, god bless eng subs, god bless their makers, god bless everybody in general
@Sonictriforce Your statement is correct, although you fail to notice that he is talking about Linear Light Reactions, not Cyclic. In the previous video see 13:55.
im not sure if the electrons come back to the PS II in cyclic photophosphorylation. aren't they getting excited in the PS I and then returning to the PS I?
@grayshorts You're right. In cyclic photo phosphorylation, the electron skips PS2 and gets circulated back to PS1 by re-entering either the cytochrome complex or plastoquinone.
Also, I thought the last electron carrier in non-cyclic is ferradoxin, not plastocyanin. Correct me if I'm wrong.
AMAZING!! My botany exam doesnt seem so scary anymore :D:D Thanks!
I was so confused at the statement he made on the electrons ending up in P700! Thanks for clarifying!
if only i could pay as much attention to my teacher as i do to these videos
Right after protein Fd (Ferredoxin), there's a NADP+ reductase protein where NADP+ + H+ (proton) helps make NADPH ultimately for use of Calvin Cycle.
Also, for cyclic photophosphorylation or cyclic electron flow, the proteins involved for the electron transport chain is PS I, Ferredoxin, Cytochrome complex, and Plastocyanin, then back to PS I. I don't think the electron transport chain goes as far back as PS II? We're only concerned about Chorophyll a (P700) in PS I when we're on Cyclic electron flow. Yes, ATP is the product of cyclic electron flow and no NADPH. Thank you for the upload! Glad to review this.
Yes, in cyclic photophosphorylation PSII is not involved, I guess there's some misunderstanding here
You are amazing !!!! I am going to pass my test now
Thank you so much for existing! I mean that from the very bottom of my heart!
thank you! Cramming for my ap bio exam and every minute is needed haha
khan you are a genius, thanks for uploading
YOUR TEN TIMES BETTER THAN MY PROFESSOR!
although im spanish, i think i couldnt have ever received a better explanation, THANKSS
Super duper helpful. You turned this concept from meaningless gibberish to something I can actually understand and respect
@grayshorts This isnt cyclic phosphorylation.Its non-cyclic which does involve PS1 as well as PS2.
OMG I hope I pass my test with this sense my textbook is so complicated. Thank you for making this :)
it has been 10 years )
Great video , understood it fully but are unsure when you say at 16:43 that the electron return to ps11 I think it returns back to ps1 when it's in a lower energy state ? Thanks
I love that I can watch this now and make corrections ... @13:10 is all wrong. Cytochrome is missing & then its waaaay more complicated than that just 'pumping' H+
The biology version of spark notes and wolfram alpha. Awesome accent included :D
Sir but ps 2 is not involved in cyclic photophosphorylation
Sal, you're my hero
I'm as excited as these electrons hit by photons for my exam tomorrow including photosynthesis krebs cycle nitrogen cycle and eveery knowledge you can ever find in the thickest bio books
Yay
I'm a peruvian Student and I lern biology in german. But anyway this video is totally helpful for me. Muchas gracias
I'm not sure but on the cyclic, instead of going back to the photosytem2, isn't it supposed to go back to PQ and not PS2?
Thank you Khan academy, I learned a lot!
Thanks Khan. I love your videos
I have a question , in lumen why water oxidized to form oxygen and protons while water is a highly stable molecule. In other words which force cause water to get oxidized ?? Answer me plzz
@Sonictriforce if electrons go from fd to b6f, then where do the H+ protons get pumped in?
cuz in a non-cyclic cycle it comes in through PQ right =\
Can someone remind me what the main difference is between how ATP is produced by oxidative phosphorylation in respiration, and how it is produced in photosynthesis?
I was under the impression that it is the membrane-bound Fo portion of ATP synthase that spins to release H+ ions back into the stroma. I believe that the F1 portion (in the stroma) was held in place by a separate rigid membrane-bound structure.
@whattacock
OIL acronym means "oxidize is losing"
RIG acronym means" reduction is gaining"
mr. khan cyclic photophosphrylation does not end up back in PS II - it does end up in the PS II electron transport chain though
ohhhhh... missed that.. XD thanks.. so basically the electron passing through the transfer chain "merger" with one of the H+ in the stroma and then bond to the NADP+ creating NADPH.... right??
do the H+'s from water also get out from the lumen via the atp synthase?
I hope I'm not too late:
There are actually hydrogens being used in the production of NADPH. The hydrogens used in the NADP+ are in a kind of a cycle, they're being recycled so to speak. They are already in the STROMA, so the NADP+, the e- and the H+ become NADPH with the NADP reductase.
Hope this helps. Ask if you didn't understand. ^__^
This comment was 10 yrs ago, hope you're doing well! If I may ask, what do you mean by "the hydrogens are in a kind of *cycle* "? Aren't they just floating around the stroma, going with the flow of the concentration gradient?
@@jamesarnoldd I went and retracted in another comment lmao. I don't remember any of this tbh
@@FranciscoJxL oh- hmm alright then thx
Correct me if I'm wrong but I believe that cyclic photophosphorlylation does NOT use Photosystem 2, only Photosystem 1. At 16:50 you draw the electron going back to PS2, but it should go back to PS1.
Otherwise, great lecture.
he says in cyclic the elctron falls into the PS 2 but doesnt cyclic phosphorylation only invovle PS1??
True
+Tasty Watermelon
That's true the electron does not fall into ps2 but actually falls to cyt b6
i still dont get why and when this happens tho
I actually paused the video to address this, so many errors in this video *SIGH*
Hi there, I have a slight doubt. We have told that in both photosistems, photons doesn't excite straightly the chlorophyll a but it is picked by some other pigments or antennas on the outside of the photosistems and then the energy of the photon passes through these complexes of molecules and finally reaches the chlorophyll a in the centre of the photosistems. We have also told that the energy of the photons is transferred from the other pigments to chlorophyll a thanks to resonance energy. Here is my doubt: how does this resonance energy actually work? He said we can immagine it as a vibration but i still have doubts about how actually the resonance occurs. Like so much these videos by the way, great work.
Refer to the Resonance video of Khan Academy Organic Chemistry.You'll surely understand the concept from it.
Great job!
i love you so much. i really wish you were my teacher.
How many ATP are produced in cyclic photophosphorylation? If two explain me the pathway of ATPs formation.
okay so when the hydrogens are taken off of H20, are those hydrogens already in the lumen or are they in the stroma? if they are already in the lumen, where are the hydrogens in the stroma coming from?
very special thank u for ur efforts
How does Light Energy (photons) "excite" electrons? Is there other examples of electrical response to light?
Yes, the emitionspectrum. The Northern Light is a good example
someone confused the dislike button with the like button but dont worry, every one can make a mistake, except for the guy who does this videos he is always right
And now I can pass my biology a-level :D
Thank you so much!
I like how he called the electron dude.
Thank you. That's life saving
4:58 any reason as to why he changed color for the remaining names here?
The ones after Plastoquinone are not part of PSII
I don't think the electron goes to photostream 2 in cyclic photophosphorylation. Does it?
Photosystem*
These videos are soooo helpful thank you!
Sal for President!
At what level is this taught? Secondary schools?
Love Khan Academy!
@Sonictriforce Excuse my ignorance, and I'm sorry if I'm wrong, but my textbook says exactly what the person says in the video. It's a high school textbook so I maybe the authors were trying to make it less complicated for us, but it says so nevertheless. Again, I'm sorry if I'm wrong :)
Thank you for saving my life!
i like his drawings
what about the oxygen evolving complex?
What are the 2 products of cyclic phosphorilization? (Bc we are being asked for 2 products, not just 1)
@undagr0undvibes it sounds about right. Instead of going to PS2, I believe it'll go back to PQ.
So why does the cell use both pathways if they both produce energy?
Great video.
You saved me. Thanks so much!
thank u so much !!!
it feels like you're in slow motion
i dont understand the part with NADP+ becoming NADPH.. how does the electron make a H?? if it was NADPH+, then it wud make sense... help anyone? but its a superly awesome video...
@luisdemasiado Well, sure he's completely right with most of the stuff, but yes, when it comes to cyclic photo phosphorylation, the electron is transferred only in PS1 in a cyclic manner and doesn't even tough PS2 cuz plastocyanin transfers the electron to P700, which further transfers it to FRS, then to ferredoxin, to cyt b6, then to cyt f, back to plastocyanin and again to P700... and this cycle keeps going on, but P680 has absolutely nothing to do with cyclic photo phosphorylation.
@torresisbeast1 I did pass my test, but my teacher made the test extra hard on purpose (he told us). He started asking all of these application questions that no-one understood. I got all the fact-based things right though (things like 'How are the lost electrons replaced after they are used in Photosystem II?). On top of that, my test was also on Cellular Respiration so it's double trouble lol.
Ahahahahah "and maybe we can breathe."
Pun intended?
i can't find the video before this one, anyone know where i can find it?
I'm learning. Anyone can answer that knows the answer. How do photons penetrate the Cell wall and stroma to reach the Thylacoid?
+Jonathon Shafer
Photons are electromagnetic radiations or packets of light. These are mass less.
Consider them like subatomic particles though they are not but size wise. Radiations don't need penetrating.
Of course the electron gets excited, he gets to approach the lumen.
I want to meet the face behind this voice 😊
2 dislikes are from people who took the time to watch the videos, didn't take the time to even listen to what he was saying and went into their exam thinking they were a pro. oh btw they failed miserably
Well you are learning from him so technically he is your teacher.
Legend Fam. your real help
Lol, he is so funny!!
The photons coming form 93 million miles away!!
I'm just wondering if the correction is made? I don't want to learn the wrong thing or else it's hard to take the wrong info out o fmy head~.~
anyways! This is awesome!!
Saves my life!!!!!!
Wow. Now I feel like a genius.........