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21 Dec 2025
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AQA GCSE Biology: Unit 2 - Mastering Plant Functions and Processes
Aarush Balouria
@aarushbalouria
1 / 6
Leaf Structure and Specialised Tissues
Your leaf is basically a photosynthesis factory with multiple floors, each designed for specific tasks. The palisade mesophyll sits at the top layer, packed with tall, thin cells crammed full of chloroplasts - think of them as solar panels positioned to catch maximum sunlight.
Below that, you'll find the spongy mesophyll, which looks completely different. These irregularly-shaped cells are loosely packed with air spaces everywhere, creating a massive surface area for gas exchange. They've got fewer chloroplasts because their main job isn't photosynthesis - it's letting carbon dioxide flow in and oxygen flow out.
The epidermis acts like the leaf's protective skin. It's covered in a waxy cuticle that works like waterproof coating, preventing the plant from losing precious water through evaporation. Aquatic plants don't bother with this waxy layer since they're surrounded by water anyway.
Key Point: Stomata are tiny pores controlled by guard cells that can open and close like gates, balancing the plant's need for gas exchange with preventing water loss.
Root Hair Cells and Water Absorption
Down in the soil, root hair cells are working overtime to keep your plant hydrated and fed. These cells are covered in tiny projections that dramatically increase their surface area - imagine having thousands of tiny straws all absorbing water and minerals simultaneously.
Each root hair cell is packed with mitochondria because they need loads of energy for active transport. Unlike simple diffusion, active transport moves substances from low to high concentration (against the natural flow), which requires energy from respiration.
The cell structure is beautifully simple: a large vacuole for storage, cytoplasm full of mitochondria for energy, and that crucial cell membrane controlling what gets in and out.
Top Tip: Active transport is essential because plants often need to absorb minerals even when there's more inside the plant than in the soil - they're literally working against nature!
Factors Affecting Transpiration Rate
Four main environmental factors control how fast plants lose water. High temperature makes water molecules move faster, increasing evaporation from cell surfaces and speeding up diffusion out of leaves.
Low humidity (dry air) creates a steeper concentration gradient, so water vapour diffuses more rapidly from the moist leaf interior into the dry outside air. Air movement (wind) removes water vapour from around leaves, maintaining this steep gradient and increasing transpiration rate.
Light intensity affects transpiration indirectly - more light increases photosynthesis rates, causing more stomata to open, which increases water loss. When plants are water-stressed, leaves wilt and collapse, reducing surface area available for evaporation.
Adaptation Alert: Xerophytes like cacti have evolved special features to survive in dry environments - think thick waxy cuticles, reduced leaf surface area, and water storage tissues.
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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.
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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.
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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.
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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.
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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
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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
AQA GCSE Biology: Unit 2 - Mastering Plant Functions and Processes
Aarush Balouria
@aarushbalouria
Ever wondered how a leaf is perfectly designed to make food whilst not dying from water loss? Plant tissues work together like a well-organised team, with each layer having a specific job that keeps the plant alive and thriving.
Leaf Structure and Specialised Tissues
Your leaf is basically a photosynthesis factory with multiple floors, each designed for specific tasks. The palisade mesophyll sits at the top layer, packed with tall, thin cells crammed full of chloroplasts - think of them as solar panels positioned to catch maximum sunlight.
Below that, you'll find the spongy mesophyll, which looks completely different. These irregularly-shaped cells are loosely packed with air spaces everywhere, creating a massive surface area for gas exchange. They've got fewer chloroplasts because their main job isn't photosynthesis - it's letting carbon dioxide flow in and oxygen flow out.
The epidermis acts like the leaf's protective skin. It's covered in a waxy cuticle that works like waterproof coating, preventing the plant from losing precious water through evaporation. Aquatic plants don't bother with this waxy layer since they're surrounded by water anyway.
Key Point: Stomata are tiny pores controlled by guard cells that can open and close like gates, balancing the plant's need for gas exchange with preventing water loss.
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Root Hair Cells and Water Absorption
Down in the soil, root hair cells are working overtime to keep your plant hydrated and fed. These cells are covered in tiny projections that dramatically increase their surface area - imagine having thousands of tiny straws all absorbing water and minerals simultaneously.
Each root hair cell is packed with mitochondria because they need loads of energy for active transport. Unlike simple diffusion, active transport moves substances from low to high concentration (against the natural flow), which requires energy from respiration.
The cell structure is beautifully simple: a large vacuole for storage, cytoplasm full of mitochondria for energy, and that crucial cell membrane controlling what gets in and out.
Top Tip: Active transport is essential because plants often need to absorb minerals even when there's more inside the plant than in the soil - they're literally working against nature!
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Factors Affecting Transpiration Rate
Four main environmental factors control how fast plants lose water. High temperature makes water molecules move faster, increasing evaporation from cell surfaces and speeding up diffusion out of leaves.
Low humidity (dry air) creates a steeper concentration gradient, so water vapour diffuses more rapidly from the moist leaf interior into the dry outside air. Air movement (wind) removes water vapour from around leaves, maintaining this steep gradient and increasing transpiration rate.
Light intensity affects transpiration indirectly - more light increases photosynthesis rates, causing more stomata to open, which increases water loss. When plants are water-stressed, leaves wilt and collapse, reducing surface area available for evaporation.
Adaptation Alert: Xerophytes like cacti have evolved special features to survive in dry environments - think thick waxy cuticles, reduced leaf surface area, and water storage tissues.
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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?
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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