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10 Dec 2025
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Comprehensive Biology Notes on Photosynthesis
raniya
@raniya
1 / 5
What Is Photosynthesis?
Think of photosynthesis as nature's way of cooking - plants use sunlight as their energy source to whip up a meal of glucose (sugar) from simple ingredients. This amazing process happens mainly in the leaves, where tiny structures called chloroplasts contain a green chemical called chlorophyll that captures light energy.
The recipe is surprisingly simple: carbon dioxide from the air plus water from the soil, mixed with sunlight energy, creates glucose and releases oxygen as a bonus. This is why we can breathe - plants are constantly pumping out oxygen during photosynthesis!
To prove that a leaf has been busy making food, scientists use the starch test. You boil the leaf to kill it, soak it in ethanol to remove the green colour, then add iodine solution. If the leaf turns blue-black, it's been making starch (stored glucose) - proof that photosynthesis happened!
Quick Tip: Remember the word equation - Carbon dioxide + Water → Glucose + Oxygen (with sunlight and chlorophyll needed)
Testing What Plants Need
Scientists love proving things work, so they've designed clever experiments to show exactly what plants need for photosynthesis. Want to prove light is essential? Cover part of a leaf with tinfoil for 24 hours, then test for starch - only the uncovered bits will test positive!
The chlorophyll experiment uses variegated leaves (ones with green and white patches). After keeping the plant in darkness then light, only the green parts test positive for starch. This proves you need that green stuff to make food!
Iodine solution is your best mate for these experiments. It's like a food detector - turns yellow-brown when there's no starch, but goes blue-black when starch is present. Dead handy for seeing exactly where photosynthesis happened on a leaf.
Once plants make glucose, they're quite clever with it. Some gets used immediately for respiration (plant breathing), some gets stored as starch or oils for later, some becomes cellulose for strong cell walls, and some makes proteins for growth.
Remember: Plants are basically living factories - they make their food, then decide whether to eat it now, save it, or use it for building materials!
Plant Nutrition and Leaf Structure
Just like you need vitamins and minerals to grow properly, plants need specific minerals from the soil to stay healthy. Nitrogen helps make chlorophyll , magnesium is essential for growth, and calcium builds strong cell walls. Missing any of these leads to stunted, unhealthy plants.
Leaves are perfectly designed for photosynthesis - they're like solar panels with built-in plumbing! The wax cuticle acts as waterproofing, whilst the palisade mesophyll layer is packed tight with chloroplasts to catch maximum light. The spongy mesophyll has air spaces for gas exchange.
Stomata (tiny pores) are the leaf's breathing holes, controlled by guard cells that open and close them. These let carbon dioxide in and oxygen out - essential for photosynthesis to work.
The stomata experiment proves how important these pores are. Cover them with Vaseline and the leaf can't photosynthesise properly because gases can't get in or out!
Cool Fact: A single leaf can have thousands of stomata - they're like tiny doors constantly opening and closing to control what goes in and out!
Respiration vs Photosynthesis
Don't get confused - respiration is the opposite of photosynthesis! Whilst photosynthesis makes glucose using sunlight, respiration breaks down glucose to release energy. Plants do both processes, just like how you eat food then use it for energy.
The respiration equation is: glucose + oxygen → energy + carbon dioxide + water. Notice how this is basically photosynthesis backwards? Plants photosynthesise during the day when there's light, but they respire all the time - day and night.
Think of it as the plant's energy cycle: photosynthesis creates the fuel (glucose), then respiration burns that fuel to power everything the plant needs to do - growing, moving water around, making new cells, and staying alive.
Key Point: Photosynthesis = making food with light energy; Respiration = using that food to release energy for life processes
Investigating Photosynthesis Rate
You can actually measure how fast photosynthesis happens using pondweed and a simple setup! As the plant photosynthesises underwater, it releases oxygen bubbles that you can count. More bubbles = faster photosynthesis.
The classic experiment involves placing a desk lamp at different distances from the pondweed and counting bubbles per minute. You'll discover that light intensity massively affects the rate - closer light means more bubbles, further away means fewer bubbles.
This experiment shows that photosynthesis isn't just on or off - it can happen faster or slower depending on conditions. Temperature, carbon dioxide levels, and light intensity all affect the rate.
Pro Tip: Always let the pondweed settle for 5 minutes before counting - this lets it adjust to the new light conditions and gives you more accurate results!
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Thomas R
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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
Comprehensive Biology Notes on Photosynthesis
raniya
@raniya
Photosynthesis is one of the most important processes on Earth - it's how plants make their own food using sunlight! Understanding how this works will help you grasp why plants are green, how they survive, and why they're essential for... Show more
What Is Photosynthesis?
Think of photosynthesis as nature's way of cooking - plants use sunlight as their energy source to whip up a meal of glucose (sugar) from simple ingredients. This amazing process happens mainly in the leaves, where tiny structures called chloroplasts contain a green chemical called chlorophyll that captures light energy.
The recipe is surprisingly simple: carbon dioxide from the air plus water from the soil, mixed with sunlight energy, creates glucose and releases oxygen as a bonus. This is why we can breathe - plants are constantly pumping out oxygen during photosynthesis!
To prove that a leaf has been busy making food, scientists use the starch test. You boil the leaf to kill it, soak it in ethanol to remove the green colour, then add iodine solution. If the leaf turns blue-black, it's been making starch (stored glucose) - proof that photosynthesis happened!
Quick Tip: Remember the word equation - Carbon dioxide + Water → Glucose + Oxygen (with sunlight and chlorophyll needed)
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Testing What Plants Need
Scientists love proving things work, so they've designed clever experiments to show exactly what plants need for photosynthesis. Want to prove light is essential? Cover part of a leaf with tinfoil for 24 hours, then test for starch - only the uncovered bits will test positive!
The chlorophyll experiment uses variegated leaves (ones with green and white patches). After keeping the plant in darkness then light, only the green parts test positive for starch. This proves you need that green stuff to make food!
Iodine solution is your best mate for these experiments. It's like a food detector - turns yellow-brown when there's no starch, but goes blue-black when starch is present. Dead handy for seeing exactly where photosynthesis happened on a leaf.
Once plants make glucose, they're quite clever with it. Some gets used immediately for respiration (plant breathing), some gets stored as starch or oils for later, some becomes cellulose for strong cell walls, and some makes proteins for growth.
Remember: Plants are basically living factories - they make their food, then decide whether to eat it now, save it, or use it for building materials!
Sign up to see the contentIt's free!
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Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
Plant Nutrition and Leaf Structure
Just like you need vitamins and minerals to grow properly, plants need specific minerals from the soil to stay healthy. Nitrogen helps make chlorophyll , magnesium is essential for growth, and calcium builds strong cell walls. Missing any of these leads to stunted, unhealthy plants.
Leaves are perfectly designed for photosynthesis - they're like solar panels with built-in plumbing! The wax cuticle acts as waterproofing, whilst the palisade mesophyll layer is packed tight with chloroplasts to catch maximum light. The spongy mesophyll has air spaces for gas exchange.
Stomata (tiny pores) are the leaf's breathing holes, controlled by guard cells that open and close them. These let carbon dioxide in and oxygen out - essential for photosynthesis to work.
The stomata experiment proves how important these pores are. Cover them with Vaseline and the leaf can't photosynthesise properly because gases can't get in or out!
Cool Fact: A single leaf can have thousands of stomata - they're like tiny doors constantly opening and closing to control what goes in and out!
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Improve your grades
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Respiration vs Photosynthesis
Don't get confused - respiration is the opposite of photosynthesis! Whilst photosynthesis makes glucose using sunlight, respiration breaks down glucose to release energy. Plants do both processes, just like how you eat food then use it for energy.
The respiration equation is: glucose + oxygen → energy + carbon dioxide + water. Notice how this is basically photosynthesis backwards? Plants photosynthesise during the day when there's light, but they respire all the time - day and night.
Think of it as the plant's energy cycle: photosynthesis creates the fuel (glucose), then respiration burns that fuel to power everything the plant needs to do - growing, moving water around, making new cells, and staying alive.
Key Point: Photosynthesis = making food with light energy; Respiration = using that food to release energy for life processes
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
Investigating Photosynthesis Rate
You can actually measure how fast photosynthesis happens using pondweed and a simple setup! As the plant photosynthesises underwater, it releases oxygen bubbles that you can count. More bubbles = faster photosynthesis.
The classic experiment involves placing a desk lamp at different distances from the pondweed and counting bubbles per minute. You'll discover that light intensity massively affects the rate - closer light means more bubbles, further away means fewer bubbles.
This experiment shows that photosynthesis isn't just on or off - it can happen faster or slower depending on conditions. Temperature, carbon dioxide levels, and light intensity all affect the rate.
Pro Tip: Always let the pondweed settle for 5 minutes before counting - this lets it adjust to the new light conditions and gives you more accurate results!
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.
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4.8/5
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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