Ever wondered how plants transport water from their roots to... Show more
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
Subjects
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
Show all topics
124
•
9 Dec 2025
•
abby
@aabby.reidd
Ever wondered how plants transport water from their roots to... Show more





Transpiration is basically how plants move water from their roots up to their leaves, where it evaporates through tiny pores called stomata. Think of it like a plant's drinking and sweating system combined! Water enters through root hair cells by osmosis, travels up the xylem vessels (which are strengthened with lignin rings), and eventually evaporates from the leaves.
Guard cells act like bouncers at the stomata, controlling whether they're open or closed and therefore how much water the plant loses. High temperatures, wind, and large surface areas increase transpiration, whilst high humidity decreases it.
Plants have two main transport systems: xylem (dead tissue that carries water and minerals upwards) and phloem (living tissue with companion cells that transports sugars in both directions). The phloem contains sieve plates and tubes that allow sugar to move between cells.
Key Insight: Just like humans have blood vessels, plants have their own "plumbing system" - xylem and phloem work together to keep plants hydrated and fed.
Your circulatory system works similarly but uses three types of blood vessels. Arteries carry blood away from your heart with thick, muscular walls to handle high pressure. Veins bring blood back to your heart with thinner walls, valves to prevent backflow, and wider channels for lower pressure. Capillaries have walls just one cell thick, creating massive networks in your tissues for efficient material exchange.

Respiration is how your cells unlock energy from glucose - it's happening in every cell right now as you read this! This enzyme-controlled process generates ATP, which is basically your body's energy currency.
Aerobic respiration (with oxygen) happens in two stages: glycolysis in the cytoplasm breaks glucose into pyruvate (making 2 ATP), then the main event occurs in the mitochondria, producing loads more ATP plus carbon dioxide and water as waste products.
When oxygen isn't available, cells switch to fermentation. In animals, this produces lactate and only 2 ATP (which is why you get muscle fatigue during intense exercise). In plants and yeast, fermentation creates ethanol and carbon dioxide - that's how bread rises and alcohol is made!
Remember: Aerobic respiration gives you way more energy (lots of ATP) than fermentation (just 2 ATP), which is why you can't sprint forever without getting tired.

Every cell is like a busy factory with specific parts doing different jobs. The cell membrane controls what enters and exits, whilst the nucleus contains all your genetic information. Mitochondria are the powerhouses where respiration happens, and ribosomes are protein-making machines.
DNA is a double-stranded helix held together by complementary base pairs (Adenine with Thymine, Guanine with Cytosine). Sections called genes contain instructions for making specific proteins.
Three key transport processes move substances around cells. Diffusion moves molecules from high to low concentration (no energy needed). Osmosis is the same but specifically for water through a selectively permeable membrane. Active transport moves substances against the concentration gradient, which requires energy and special membrane proteins.
Top Tip: Think of diffusion like students leaving school - they naturally spread from crowded corridors to empty spaces without any effort needed.
Proteins are made when mRNA copies the genetic code from DNA in the nucleus and takes it to ribosomes for assembly. These proteins become enzymes (biological catalysts), hormones, antibodies, or structural components.

Mitosis is how your body grows and repairs itself by creating identical diploid cells (46 chromosomes). During mitosis, chromosomes line up, spindle fibres pull chromatids apart, and the cytoplasm divides to form two identical cells.
Stem cells are special because they can both copy themselves and become specialised cell types. Embryonic stem cells can become any cell type, whilst tissue stem cells are more limited but less controversial.
Your nervous system works like an incredibly fast communication network. Receptors detect stimuli, sensory neurons send messages to your brain and spinal cord (CNS), interneurons process the information, and motor neurons tell effectors (muscles and glands) how to respond.
Brain Breakdown: Your cerebrum handles conscious thoughts and memory, your cerebellum controls balance, and your medulla manages vital functions like breathing and heart rate - all automatically!
Reproduction involves male and female gametes (sex cells with 23 chromosomes each). In humans, sperm from testes meets an egg in the oviduct. Variation in offspring comes in two types: discrete (distinct groups like blood type) caused by single genes, and continuous (ranges like height) caused by multiple genes working together.
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
App 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
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
abby
@aabby.reidd
Ever wondered how plants transport water from their roots to their leaves, or how your heart pumps blood around your body? This biology content covers the essential transport systems in both plants and animals, plus key processes like respiration, cell... Show more

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Transpiration is basically how plants move water from their roots up to their leaves, where it evaporates through tiny pores called stomata. Think of it like a plant's drinking and sweating system combined! Water enters through root hair cells by osmosis, travels up the xylem vessels (which are strengthened with lignin rings), and eventually evaporates from the leaves.
Guard cells act like bouncers at the stomata, controlling whether they're open or closed and therefore how much water the plant loses. High temperatures, wind, and large surface areas increase transpiration, whilst high humidity decreases it.
Plants have two main transport systems: xylem (dead tissue that carries water and minerals upwards) and phloem (living tissue with companion cells that transports sugars in both directions). The phloem contains sieve plates and tubes that allow sugar to move between cells.
Key Insight: Just like humans have blood vessels, plants have their own "plumbing system" - xylem and phloem work together to keep plants hydrated and fed.
Your circulatory system works similarly but uses three types of blood vessels. Arteries carry blood away from your heart with thick, muscular walls to handle high pressure. Veins bring blood back to your heart with thinner walls, valves to prevent backflow, and wider channels for lower pressure. Capillaries have walls just one cell thick, creating massive networks in your tissues for efficient material exchange.

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Respiration is how your cells unlock energy from glucose - it's happening in every cell right now as you read this! This enzyme-controlled process generates ATP, which is basically your body's energy currency.
Aerobic respiration (with oxygen) happens in two stages: glycolysis in the cytoplasm breaks glucose into pyruvate (making 2 ATP), then the main event occurs in the mitochondria, producing loads more ATP plus carbon dioxide and water as waste products.
When oxygen isn't available, cells switch to fermentation. In animals, this produces lactate and only 2 ATP (which is why you get muscle fatigue during intense exercise). In plants and yeast, fermentation creates ethanol and carbon dioxide - that's how bread rises and alcohol is made!
Remember: Aerobic respiration gives you way more energy (lots of ATP) than fermentation (just 2 ATP), which is why you can't sprint forever without getting tired.

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Every cell is like a busy factory with specific parts doing different jobs. The cell membrane controls what enters and exits, whilst the nucleus contains all your genetic information. Mitochondria are the powerhouses where respiration happens, and ribosomes are protein-making machines.
DNA is a double-stranded helix held together by complementary base pairs (Adenine with Thymine, Guanine with Cytosine). Sections called genes contain instructions for making specific proteins.
Three key transport processes move substances around cells. Diffusion moves molecules from high to low concentration (no energy needed). Osmosis is the same but specifically for water through a selectively permeable membrane. Active transport moves substances against the concentration gradient, which requires energy and special membrane proteins.
Top Tip: Think of diffusion like students leaving school - they naturally spread from crowded corridors to empty spaces without any effort needed.
Proteins are made when mRNA copies the genetic code from DNA in the nucleus and takes it to ribosomes for assembly. These proteins become enzymes (biological catalysts), hormones, antibodies, or structural components.

Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Mitosis is how your body grows and repairs itself by creating identical diploid cells (46 chromosomes). During mitosis, chromosomes line up, spindle fibres pull chromatids apart, and the cytoplasm divides to form two identical cells.
Stem cells are special because they can both copy themselves and become specialised cell types. Embryonic stem cells can become any cell type, whilst tissue stem cells are more limited but less controversial.
Your nervous system works like an incredibly fast communication network. Receptors detect stimuli, sensory neurons send messages to your brain and spinal cord (CNS), interneurons process the information, and motor neurons tell effectors (muscles and glands) how to respond.
Brain Breakdown: Your cerebrum handles conscious thoughts and memory, your cerebellum controls balance, and your medulla manages vital functions like breathing and heart rate - all automatically!
Reproduction involves male and female gametes (sex cells with 23 chromosomes each). In humans, sperm from testes meets an egg in the oviduct. Variation in offspring comes in two types: discrete (distinct groups like blood type) caused by single genes, and continuous (ranges like height) caused by multiple genes working together.
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.
You can download the app from Google Play Store and Apple App Store.
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
Explore the essential functions and structures of cell membranes, including the fluid mosaic model, phospholipid bilayer, and the role of membrane proteins. This summary covers how membranes regulate substance movement, compartmentalize cellular functions, and facilitate communication within and outside the cell.
Explore key concepts in cell biology, including DNA structure, protein synthesis, cellular respiration, and genetic engineering. This summary covers essential processes such as glycolysis, fermentation, and enzyme functions, providing a comprehensive overview for students studying cellular structures and functions. Ideal for Nat 5 Biology revision.
Explore key concepts of cell structure and function in this comprehensive glossary. Understand the roles of organelles, transport mechanisms, and cellular processes essential for A-level biology. Ideal for students seeking clarity on cell anatomy, membrane transport, and the differences between eukaryotic and prokaryotic cells.
Explore the key organelles of eukaryotic cells, including their structures and functions. This summary covers the nucleus, mitochondria, chloroplasts, Golgi apparatus, lysosomes, ribosomes, endoplasmic reticulum, cell wall, vacuoles, and cytoskeleton. Ideal for students studying cell biology and looking for a concise reference on organelle functions and characteristics.
Explore the structure of biological membranes and the various transport mechanisms including simple diffusion, facilitated diffusion, and active transport. This summary covers key concepts such as glycolipids, glycoproteins, and the phospholipid bilayer, essential for A-Level Biology students across all exam boards (OCR, Edexcel, AQA).
Explore key concepts in NAT5 Biology with this comprehensive summary covering proteins, enzymes, DNA structure, cellular respiration, and genetic engineering. Understand the roles of organelles, protein synthesis, and transport mechanisms like diffusion and osmosis. Ideal for exam preparation and quick revision.
App 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
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