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Updated Mar 24, 2026
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Understanding the Kidney in Biology
Evelyn Ridley
@ev_alice
How Your Kidneys Keep You Alive
Think of your kidneys as your body's ultimate bouncer - they decide what stays and what goes. Their main job is maintaining water levels whilst filtering out nasty waste products like urea and excess ions from your blood.
The clever bit happens in tiny structures called kidney tubules, where a process called selective reabsorption takes place. Your kidneys don't just chuck everything out - they're smart enough to save the good stuff like glucose, essential water, and useful ions that your body actually needs.
ADH (antidiuretic hormone) acts like your kidney's volume control. When you're dehydrated, your pituitary gland releases ADH, making your kidney tubules more permeable so they can grab more water back. Once your water levels are sorted, ADH production stops - that's negative feedback in action.
Quick Tip: Remember that selective reabsorption is selective for a reason - it only reabsorbs what your body needs, not everything that gets filtered out!
When Kidneys Fail: Treatment Options
When kidneys pack up completely, you've got kidney failure - and two main treatment routes to consider. Kidney transplants are the gold standard, involving swapping a dodgy kidney for a working one from a donor.
The catch? You might wait ages for a suitable donor, and there's always the risk of rejection where your immune system attacks the new kidney. Family donors reduce this risk, and immunosuppressive medicines help too, though they come with their own side effects.
Dialysis is your backup option - essentially an external kidney machine. It filters your blood through dialysis fluid, doing the job your kidneys can't manage anymore. Patients need treatment at least three times weekly for several hours each session.
Whilst dialysis keeps people alive, it's expensive, time-consuming, and requires strict dietary restrictions. It's brilliant for buying time whilst waiting for a transplant, but it's definitely not as convenient as having working kidneys.
Real Talk: Most patients prefer transplants over lifelong dialysis, but dialysis is often the only option available immediately after kidney failure.
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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.
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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.
Rohan U
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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.
Xander S
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THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
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Paul T
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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.
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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
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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
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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.
David K
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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
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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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Understanding the Kidney in Biology
Evelyn Ridley
@ev_alice
Your kidneys are basically your body's brilliant filtration system, working 24/7 to keep you healthy by removing waste and maintaining the perfect water balance. Understanding how they work and what happens when they fail is crucial for your biology studies... Show more
How Your Kidneys Keep You Alive
Think of your kidneys as your body's ultimate bouncer - they decide what stays and what goes. Their main job is maintaining water levels whilst filtering out nasty waste products like urea and excess ions from your blood.
The clever bit happens in tiny structures called kidney tubules, where a process called selective reabsorption takes place. Your kidneys don't just chuck everything out - they're smart enough to save the good stuff like glucose, essential water, and useful ions that your body actually needs.
ADH (antidiuretic hormone) acts like your kidney's volume control. When you're dehydrated, your pituitary gland releases ADH, making your kidney tubules more permeable so they can grab more water back. Once your water levels are sorted, ADH production stops - that's negative feedback in action.
Quick Tip: Remember that selective reabsorption is selective for a reason - it only reabsorbs what your body needs, not everything that gets filtered out!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
When Kidneys Fail: Treatment Options
When kidneys pack up completely, you've got kidney failure - and two main treatment routes to consider. Kidney transplants are the gold standard, involving swapping a dodgy kidney for a working one from a donor.
The catch? You might wait ages for a suitable donor, and there's always the risk of rejection where your immune system attacks the new kidney. Family donors reduce this risk, and immunosuppressive medicines help too, though they come with their own side effects.
Dialysis is your backup option - essentially an external kidney machine. It filters your blood through dialysis fluid, doing the job your kidneys can't manage anymore. Patients need treatment at least three times weekly for several hours each session.
Whilst dialysis keeps people alive, it's expensive, time-consuming, and requires strict dietary restrictions. It's brilliant for buying time whilst waiting for a transplant, but it's definitely not as convenient as having working kidneys.
Real Talk: Most patients prefer transplants over lifelong dialysis, but dialysis is often the only option available immediately after kidney failure.
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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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
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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
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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.
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David K
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Sudenaz Ocak
Android user
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Stefan S
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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
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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
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Thomas R
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Basil
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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.
David K
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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 Knowunity AI. 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