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Biology
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AP Chemistry
English
AP English Literature
AP Biology
Nov 30, 2025
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3 pages
Light-dependent reactions are a crucial first stage of photosynthesis where plants convert sunlight into chemical energy. Taking place... Show more
Ever wondered how plants turn sunlight into energy? It all happens in specialized structures called thylakoid membranes inside chloroplasts of leaf cells. During light-dependent reactions, plants capture light energy to produce two important energy storage molecules ATP and NADPH. As a bonus, this process releases oxygen gas that we breathe!
This process occurs in two simultaneous ways non-cyclic photophosphorylation and cyclic photophosphorylation. These reactions take place across thousands of photosystems embedded in the thylakoid membranes.
In non-cyclic photophosphorylation, both Photosystem I and II absorb light energy. This energy excites electrons to higher energy levels until the reaction centers release them. The electrons from Photosystem II travel through an electron transport chain (ETC) before eventually reducing Photosystem I. As electrons move along this chain, their energy pumps hydrogen ions into the thylakoid space, creating a concentration gradient—similar to what happens in cellular respiration.
Amazing Fact The light-dependent reactions are nature's original solar panels, converting sunlight into usable energy with remarkable efficiency!
The hydrogen ion gradient built up inside the thylakoid stores potential energy, like water behind a dam. This stored energy will soon power ATP production.
Meanwhile, electrons leaving Photosystem I travel through another electron transport chain. These electrons are used to convert NADP+ into NADPH. Think of NADP+ as a dead battery and NADPH as a fully charged one. This "charged battery" will later provide the energy needed to build glucose molecules during the Calvin Cycle.
The concentrated hydrogen ions don't stay trapped forever. They rush through special channels in the ATP synthase enzyme, like water through a turbine. This flow of ions powers the enzyme to add a phosphate group to ADP, creating ATP—a process called chemiosmosis. The ATP will fuel glucose production in the next stage of photosynthesis.
Another important product forms during non-cyclic photophosphorylation oxygen gas. After Photosystem II loses electrons, it splits water molecules (photolysis) to replace them. This splitting releases hydrogen ions and oxygen gas. Remarkably, all of Earth's oxygen gas originated from water molecules through this process!
Think About This Every breath you take contains oxygen molecules that were once part of water in a plant somewhere!
Non-cyclic photophosphorylation produces three key products ATP and NADPH (energy storage molecules for the Calvin Cycle) and oxygen gas. The name perfectly describes how electrons move in a linear path—from water through Photosystem II, through an electron transport chain, to Photosystem I, and finally to NADP+ to make NADPH.
While this is happening, a second process called cyclic photophosphorylation occurs simultaneously. Unlike the non-cyclic pathway, this process involves only Photosystem I. Light energy absorbed by Photosystem I causes electrons to be released, but instead of ending at NADP+, these electrons travel through a different electron transport chain and circle back to Photosystem I.
As electrons move through this cyclic pathway, they also drive hydrogen ion transport into the thylakoid. These ions then flow through ATP synthase to generate ATP—the only product of cyclic photophosphorylation. No oxygen or NADPH is produced in this cyclic pathway.
The name "cyclic photophosphorylation" comes from the circular path of the electrons (cyclic) and the addition of phosphate to ADP (phosphorylation). Together, both pathways ensure plants have the energy molecules they need for the next stage of photosynthesis.
Quick Check Can you explain why plants need both cyclic and non-cyclic pathways? (Hint think about the different products each pathway creates!)
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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AP Bio, light dependent reactions review
AP Biology"Some organisms consume other organisms to obtain organic molecules these are called heterotrophs. Organisms that can produce their own organic molecules from inorganic molecules are called autotrophs."
AP BiologyThis document summarizes the Photosynthesis topic in AP Biology with concepts likes Calvin cycle, the flow of an electron, how ATP is produced, etc.
AP BiologyBiology all notes for the class
AP BiologyExplore the intricate processes of cellular metabolism, including glycolysis, Krebs cycle, and the electron transport chain. This summary covers key concepts such as ATP production, photosynthesis, and enzyme inhibition mechanisms. Ideal for IB Biology HL students seeking a comprehensive understanding of bioenergetics and metabolic pathways.
BiologyIn class notes
AP BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Light-dependent reactions are a crucial first stage of photosynthesis where plants convert sunlight into chemical energy. Taking place in the thylakoid membranes of chloroplasts, these reactions capture light energy to produce ATP and NADPH—the energy currency molecules plants need to... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered how plants turn sunlight into energy? It all happens in specialized structures called thylakoid membranes inside chloroplasts of leaf cells. During light-dependent reactions, plants capture light energy to produce two important energy storage molecules: ATP and NADPH. As a bonus, this process releases oxygen gas that we breathe!
This process occurs in two simultaneous ways: non-cyclic photophosphorylation and cyclic photophosphorylation. These reactions take place across thousands of photosystems embedded in the thylakoid membranes.
In non-cyclic photophosphorylation, both Photosystem I and II absorb light energy. This energy excites electrons to higher energy levels until the reaction centers release them. The electrons from Photosystem II travel through an electron transport chain (ETC) before eventually reducing Photosystem I. As electrons move along this chain, their energy pumps hydrogen ions into the thylakoid space, creating a concentration gradient—similar to what happens in cellular respiration.
Amazing Fact: The light-dependent reactions are nature's original solar panels, converting sunlight into usable energy with remarkable efficiency!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The hydrogen ion gradient built up inside the thylakoid stores potential energy, like water behind a dam. This stored energy will soon power ATP production.
Meanwhile, electrons leaving Photosystem I travel through another electron transport chain. These electrons are used to convert NADP+ into NADPH. Think of NADP+ as a dead battery and NADPH as a fully charged one. This "charged battery" will later provide the energy needed to build glucose molecules during the Calvin Cycle.
The concentrated hydrogen ions don't stay trapped forever. They rush through special channels in the ATP synthase enzyme, like water through a turbine. This flow of ions powers the enzyme to add a phosphate group to ADP, creating ATP—a process called chemiosmosis. The ATP will fuel glucose production in the next stage of photosynthesis.
Another important product forms during non-cyclic photophosphorylation: oxygen gas. After Photosystem II loses electrons, it splits water molecules (photolysis) to replace them. This splitting releases hydrogen ions and oxygen gas. Remarkably, all of Earth's oxygen gas originated from water molecules through this process!
Think About This: Every breath you take contains oxygen molecules that were once part of water in a plant somewhere!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Non-cyclic photophosphorylation produces three key products: ATP and NADPH (energy storage molecules for the Calvin Cycle) and oxygen gas. The name perfectly describes how electrons move in a linear path—from water through Photosystem II, through an electron transport chain, to Photosystem I, and finally to NADP+ to make NADPH.
While this is happening, a second process called cyclic photophosphorylation occurs simultaneously. Unlike the non-cyclic pathway, this process involves only Photosystem I. Light energy absorbed by Photosystem I causes electrons to be released, but instead of ending at NADP+, these electrons travel through a different electron transport chain and circle back to Photosystem I.
As electrons move through this cyclic pathway, they also drive hydrogen ion transport into the thylakoid. These ions then flow through ATP synthase to generate ATP—the only product of cyclic photophosphorylation. No oxygen or NADPH is produced in this cyclic pathway.
The name "cyclic photophosphorylation" comes from the circular path of the electrons (cyclic) and the addition of phosphate to ADP (phosphorylation). Together, both pathways ensure plants have the energy molecules they need for the next stage of photosynthesis.
Quick Check: Can you explain why plants need both cyclic and non-cyclic pathways? (Hint: think about the different products each pathway creates!)
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
4
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
AP Bio, light dependent reactions review
AP Biology"Some organisms consume other organisms to obtain organic molecules these are called heterotrophs. Organisms that can produce their own organic molecules from inorganic molecules are called autotrophs."
AP BiologyThis document summarizes the Photosynthesis topic in AP Biology with concepts likes Calvin cycle, the flow of an electron, how ATP is produced, etc.
AP BiologyBiology all notes for the class
AP BiologyExplore the intricate processes of cellular metabolism, including glycolysis, Krebs cycle, and the electron transport chain. This summary covers key concepts such as ATP production, photosynthesis, and enzyme inhibition mechanisms. Ideal for IB Biology HL students seeking a comprehensive understanding of bioenergetics and metabolic pathways.
BiologyIn class notes
AP BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
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