Ever wondered how plants make their own food and keep... Show more
Biologia
SociologySign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
211
•
3 Dec 2025
•
Photosynthesis Chapter 11 - A Level Biology
Morgan
@morganb240605
1 / 7
Overview of Photosynthesis
Think of photosynthesis as a two-stage energy conversion factory that happens inside every green leaf. Plants use this process to transform light energy into chemical energy, creating glucose (C₆H₁₂O₆) - basically plant sugar - and releasing oxygen as a bonus.
The whole process can be summed up in one equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. What this means is that plants take in carbon dioxide and water, then use light energy to make glucose and oxygen.
Leaves are perfectly designed for this job with features like large surface areas to catch maximum sunlight, thin structures so gases can move easily, and thousands of tiny stomata (breathing pores) for gas exchange. Inside the leaves, chloroplasts are the tiny green factories where all the magic happens.
There are three main stages: capturing light energy with chlorophyll, the light-dependent reaction where water gets split and ATP (energy currency) is made, and the light-independent reaction where carbon dioxide becomes glucose.
Key Point: Every breath you take contains oxygen that was produced by photosynthesis - plants literally keep us alive!
The Light-Dependent Reaction
This is where the real energy conversion begins - think of it as photosynthesis's power station. When light hits chlorophyll molecules in the thylakoids , it kicks electrons to higher energy levels in a process called photoionisation.
Here's where it gets clever: water molecules get split apart by light energy in photolysis . This provides replacement electrons for the chlorophyll and creates hydrogen ions that are crucial for making ATP.
The chemiosmotic theory explains how ATP is actually produced. Hydrogen ions get pumped into the thylakoid space, creating a concentration gradient. When these ions flow back out through ATP synthase channels, they power the creation of ATP from ADP - like water flowing through a turbine to generate electricity.
Meanwhile, NADP picks up hydrogen ions to become reduced NADP (NADPH), which acts as an electron carrier. Both ATP and NADPH are essential products that fuel the next stage of photosynthesis.
Remember: The oxygen you breathe is actually just a waste product from this reaction - what plants really want is the ATP and NADPH!
The Light-Independent Reaction (Calvin Cycle)
Despite its name, this stage still depends on the light-dependent reaction's products - it just doesn't need direct sunlight. Taking place in the stroma (the fluid inside chloroplasts), this is where carbon dioxide finally becomes useful organic molecules through the Calvin cycle.
The cycle starts when CO₂ from the air reacts with ribulose bisphosphate (RuBP), a 5-carbon sugar, thanks to an enzyme called rubisco. This creates two molecules of glycerate 3-phosphate (GP), which then gets reduced to triose phosphate (TP) using the ATP and NADPH from the light-dependent stage.
Here's the brilliant bit: some TP molecules get converted into glucose, starch, and other organic compounds the plant needs. But most TP molecules are recycled back into RuBP using more ATP, keeping the cycle spinning.
It takes six turns of the Calvin cycle to make one glucose molecule - that's 6 CO₂ molecules, 18 ATP, and 12 NADPH. The stroma is perfectly set up for this with all the necessary enzymes, plus it's right next to the grana so products can diffuse quickly between stages.
Think of it this way: The Calvin cycle is like a recycling plant that takes waste CO₂ and turns it into useful products, powered by the energy from the light reactions.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Light-dependent Reactions
Most popular content in Biology
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Photosynthesis Chapter 11 - A Level Biology
Morgan
@morganb240605
Ever wondered how plants make their own food and keep our planet alive? Photosynthesisis the incredible process where plants capture sunlight and turn it into energy, producing the oxygen we breathe and the glucose that fuels life on Earth.... Show more
Overview of Photosynthesis
Think of photosynthesis as a two-stage energy conversion factory that happens inside every green leaf. Plants use this process to transform light energy into chemical energy, creating glucose (C₆H₁₂O₆) - basically plant sugar - and releasing oxygen as a bonus.
The whole process can be summed up in one equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. What this means is that plants take in carbon dioxide and water, then use light energy to make glucose and oxygen.
Leaves are perfectly designed for this job with features like large surface areas to catch maximum sunlight, thin structures so gases can move easily, and thousands of tiny stomata (breathing pores) for gas exchange. Inside the leaves, chloroplasts are the tiny green factories where all the magic happens.
There are three main stages: capturing light energy with chlorophyll, the light-dependent reaction where water gets split and ATP (energy currency) is made, and the light-independent reaction where carbon dioxide becomes glucose.
Key Point: Every breath you take contains oxygen that was produced by photosynthesis - plants literally keep us alive!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Light-Dependent Reaction
This is where the real energy conversion begins - think of it as photosynthesis's power station. When light hits chlorophyll molecules in the thylakoids , it kicks electrons to higher energy levels in a process called photoionisation.
Here's where it gets clever: water molecules get split apart by light energy in photolysis . This provides replacement electrons for the chlorophyll and creates hydrogen ions that are crucial for making ATP.
The chemiosmotic theory explains how ATP is actually produced. Hydrogen ions get pumped into the thylakoid space, creating a concentration gradient. When these ions flow back out through ATP synthase channels, they power the creation of ATP from ADP - like water flowing through a turbine to generate electricity.
Meanwhile, NADP picks up hydrogen ions to become reduced NADP (NADPH), which acts as an electron carrier. Both ATP and NADPH are essential products that fuel the next stage of photosynthesis.
Remember: The oxygen you breathe is actually just a waste product from this reaction - what plants really want is the ATP and NADPH!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Light-Independent Reaction (Calvin Cycle)
Despite its name, this stage still depends on the light-dependent reaction's products - it just doesn't need direct sunlight. Taking place in the stroma (the fluid inside chloroplasts), this is where carbon dioxide finally becomes useful organic molecules through the Calvin cycle.
The cycle starts when CO₂ from the air reacts with ribulose bisphosphate (RuBP), a 5-carbon sugar, thanks to an enzyme called rubisco. This creates two molecules of glycerate 3-phosphate (GP), which then gets reduced to triose phosphate (TP) using the ATP and NADPH from the light-dependent stage.
Here's the brilliant bit: some TP molecules get converted into glucose, starch, and other organic compounds the plant needs. But most TP molecules are recycled back into RuBP using more ATP, keeping the cycle spinning.
It takes six turns of the Calvin cycle to make one glucose molecule - that's 6 CO₂ molecules, 18 ATP, and 12 NADPH. The stroma is perfectly set up for this with all the necessary enzymes, plus it's right next to the grana so products can diffuse quickly between stages.
Think of it this way: The Calvin cycle is like a recycling plant that takes waste CO₂ and turns it into useful products, powered by the energy from the light reactions.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Similar content
Photosynthesis Mechanisms Explained
Explore the intricate processes of photosynthesis, including light-dependent and light-independent reactions, chloroplast structure, and the role of pigments like chlorophyll. This summary covers key concepts such as thylakoids, the Calvin cycle, and the action spectrum, providing a comprehensive overview for A-level Biology students.
Biology12
Calvin Cycle Overview
Explore the Calvin Cycle, the light-independent reactions of photosynthesis occurring in the stroma. This summary covers the journey of carbon dioxide, the role of RuBISCO, ATP and NADPH in synthesizing glucose, and the regeneration of RuBP. Ideal for students studying photosynthesis and its biochemical processes.
Biology12
Cellular Respiration Overview
Explore the key processes of cellular respiration, including glycolysis, the Krebs cycle, and oxidative phosphorylation. This summary highlights ATP production, metabolic pathways, and the role of NADH and FADH2 in energy transfer. Ideal for A2 Level WJEC biology students.
Biology13
Enzyme Reaction Temperature Study
Explore the impact of temperature on enzyme activity in this practical guide. Learn to conduct experiments using trypsin and milk powder to measure reaction rates, understand enzyme kinetics, and evaluate safety protocols. Ideal for A-Level Biology students, this resource covers essential techniques, risk assessments, and data analysis methods.
Biology12
Photosynthesis Mechanisms Explained
Explore the intricate processes of photosynthesis, including the light-dependent reactions and the Calvin cycle. This summary covers key concepts such as electron transport, ATP production, and the roles of chlorophyll and NADPH. Understand how glucose is synthesized and its various uses in plant metabolism. Ideal for higher biology students seeking a comprehensive overview of photosynthesis.
BiologyS5
Krebs Cycle Overview
Explore the Krebs Cycle and Link Reaction in cellular respiration. This summary covers key processes including dehydrogenation, decarboxylation, and the formation of NADH and FADH2. Understand how Acetyl CoA interacts with Oxaloacetate to produce ATP and carbon dioxide. Ideal for A-Level Biology students studying WJEC Unit 3.
Biology12
Most popular content: Light-dependent Reactions
Most popular content in Biology
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user