Subjects
Maths
Biology
Chemistry
English Language
History
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
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1l the quest for political stability: germany, 1871-1991
Britain & the wider world: 1745 -1901
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
Biology
9 Dec 2025
139
2 pages
lucy _ @lucy__lizu
Your circulatory system is basically your body's delivery service, constantly transporting everything your cells need to survive. Understanding... Show more
Ever wondered what's actually flowing through your veins? Blood isn't just red liquid - it's made up of four key components that each have specific jobs.
Red blood cells are perfectly designed oxygen taxis. Their biconcave shape and lack of nucleus gives them maximum space to pack in haemoglobin, the iron-containing protein that grabs onto oxygen in your lungs and delivers it everywhere else.
White blood cells are your body's security team. Phagocytes literally eat harmful microorganisms, whilst lymphocytes produce antibodies - think of them as wanted posters that help identify threats. Platelets act like biological superglue, converting fibrinogen to fibrin to form clots when you're injured.
The heart has four chambers that work in pairs. The left ventricle has thicker walls than the right because it pumps blood around your entire body, whilst the right ventricle only sends blood to your lungs. Valves prevent backflow, ensuring blood always moves in the right direction through this double circulation system.
Quick Tip Remember that arteries carry blood away from the heart (both start with 'A'), whilst veins carry blood towards it. Capillaries are where the actual exchange of materials happens.
Your pulse rate shoots up during exercise because your muscle cells are screaming for more oxygen and glucose to fuel increased respiration. It's like pressing the accelerator on your body's engine.
When you exercise, your cardiac output increases dramatically. This means more blood pumps around your body each minute, creating higher blood pressure and faster blood flow to your working muscles. The result? More oxygen and glucose delivery, plus quicker removal of waste products like carbon dioxide and lactic acid.
Here's where fitness levels really show. Unfit people have higher resting heart rates, experience bigger heart rate spikes during exercise, and take much longer to recover afterwards. Their circulatory systems simply aren't as efficient at meeting the body's demands.
Think of it like comparing a well-tuned sports car to an old banger - both can get you there, but one does it much more efficiently. Regular exercise trains your heart to become a more powerful pump, just like any other muscle.
Exam Focus Be ready to explain why heart rate increases during exercise and how fitness affects recovery time - this comes up frequently in exam questions.
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 key concepts of human body organization, focusing on the circulatory and digestive systems. This summary covers the structure and function of major organs, including the heart, lungs, and digestive tract, essential for AQA Combined Science revision.
BiologyExplore key concepts in human and plant organization with this interactive study resource. Covering blood components, circulatory and digestive systems, plant structures, and the role of enzymes, this resource is designed for GCSE Biology students. Engage with active recall questions to reinforce your understanding of topics such as heart disease, cancer, and nutrient transport. Perfect for exam preparation and enhancing your knowledge of biological systems.
BiologyExplore the structure and function of the heart and blood vessels in the circulatory system. This summary covers the roles of arteries, veins, and capillaries, detailing how blood is transported throughout the body. Ideal for AQA GCSE Biology students preparing for exams.
BiologyExplore key concepts in National 5 Biology Unit 2, covering the nervous and endocrine systems, cell specialization, genetic inheritance, and biological processes. This summary includes essential topics such as mitosis, meiosis, fertilization, and the structure and function of the heart. Ideal for exam preparation and understanding biological systems. Type: Summary.
BiologyExplore the specialisation of animal and plant cells, focusing on their structures and functions. This summary covers key concepts such as muscle, nerve, red blood, root hair, xylem, and phloem cells, detailing how their adaptations enable specific roles within tissues and organs. Ideal for GCSE students preparing for exams.
BiologyExplore the functions and adaptations of blood vessels in the circulatory system. This summary covers blood flow direction, pressure differences, and the structure of arteries, veins, and capillaries, along with a diagram illustrating the heart's role in blood circulation. Ideal for understanding blood transport in humans.
BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
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
lucy _
@lucy__lizu
Your circulatory system is basically your body's delivery service, constantly transporting everything your cells need to survive. Understanding how blood, the heart, and blood vessels work together will help you ace your biology exams and understand why your heart pounds... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered what's actually flowing through your veins? Blood isn't just red liquid - it's made up of four key components that each have specific jobs.
Red blood cells are perfectly designed oxygen taxis. Their biconcave shape and lack of nucleus gives them maximum space to pack in haemoglobin, the iron-containing protein that grabs onto oxygen in your lungs and delivers it everywhere else.
White blood cells are your body's security team. Phagocytes literally eat harmful microorganisms, whilst lymphocytes produce antibodies - think of them as wanted posters that help identify threats. Platelets act like biological superglue, converting fibrinogen to fibrin to form clots when you're injured.
The heart has four chambers that work in pairs. The left ventricle has thicker walls than the right because it pumps blood around your entire body, whilst the right ventricle only sends blood to your lungs. Valves prevent backflow, ensuring blood always moves in the right direction through this double circulation system.
Quick Tip: Remember that arteries carry blood away from the heart (both start with 'A'), whilst veins carry blood towards it. Capillaries are where the actual exchange of materials happens.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your pulse rate shoots up during exercise because your muscle cells are screaming for more oxygen and glucose to fuel increased respiration. It's like pressing the accelerator on your body's engine.
When you exercise, your cardiac output increases dramatically. This means more blood pumps around your body each minute, creating higher blood pressure and faster blood flow to your working muscles. The result? More oxygen and glucose delivery, plus quicker removal of waste products like carbon dioxide and lactic acid.
Here's where fitness levels really show. Unfit people have higher resting heart rates, experience bigger heart rate spikes during exercise, and take much longer to recover afterwards. Their circulatory systems simply aren't as efficient at meeting the body's demands.
Think of it like comparing a well-tuned sports car to an old banger - both can get you there, but one does it much more efficiently. Regular exercise trains your heart to become a more powerful pump, just like any other muscle.
Exam Focus: Be ready to explain why heart rate increases during exercise and how fitness affects recovery time - this comes up frequently in exam questions.
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 key concepts of human body organization, focusing on the circulatory and digestive systems. This summary covers the structure and function of major organs, including the heart, lungs, and digestive tract, essential for AQA Combined Science revision.
BiologyExplore key concepts in human and plant organization with this interactive study resource. Covering blood components, circulatory and digestive systems, plant structures, and the role of enzymes, this resource is designed for GCSE Biology students. Engage with active recall questions to reinforce your understanding of topics such as heart disease, cancer, and nutrient transport. Perfect for exam preparation and enhancing your knowledge of biological systems.
BiologyExplore the structure and function of the heart and blood vessels in the circulatory system. This summary covers the roles of arteries, veins, and capillaries, detailing how blood is transported throughout the body. Ideal for AQA GCSE Biology students preparing for exams.
BiologyExplore key concepts in National 5 Biology Unit 2, covering the nervous and endocrine systems, cell specialization, genetic inheritance, and biological processes. This summary includes essential topics such as mitosis, meiosis, fertilization, and the structure and function of the heart. Ideal for exam preparation and understanding biological systems. Type: Summary.
BiologyExplore the specialisation of animal and plant cells, focusing on their structures and functions. This summary covers key concepts such as muscle, nerve, red blood, root hair, xylem, and phloem cells, detailing how their adaptations enable specific roles within tissues and organs. Ideal for GCSE students preparing for exams.
BiologyExplore the functions and adaptations of blood vessels in the circulatory system. This summary covers blood flow direction, pressure differences, and the structure of arteries, veins, and capillaries, along with a diagram illustrating the heart's role in blood circulation. Ideal for understanding blood transport in humans.
BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
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
