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Victor
10/12/2025
Biology
Amino Acids and Polypeptides
18
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10 Dec 2025
•
Understanding Amino Acids and Polypeptides
Victor
@the1andonly
1 / 6
Course Introduction
This is your Biology workbook for Year 12, focusing on one of the most crucial topics you'll study this year. You're about to dive into amino acids and polypeptides - the fundamental components that make life possible at the molecular level.
Why Proteins Matter
Proteins are absolutely everywhere in your body, doing jobs you probably never imagined! These polymers are built from amino acid monomers and serve more functions than any other type of molecule.
Think about what's happening in your body right now: collagen is keeping your skin strong, haemoglobin is carrying oxygen through your blood, and insulin is regulating your blood sugar. Your muscles use myosin to contract, whilst antibodies patrol your bloodstream fighting infections.
Amino acids contain four essential elements: carbon, hydrogen, oxygen, and nitrogen (some also have sulphur). They're called amino acids because they have both an amino group and a carboxyl group attached to a central carbon atom, plus a variable R group that makes each one unique.
Key insight: The R group is what makes each amino acid different - it's like each amino acid's unique fingerprint that determines its properties and role in proteins.
Amino Acid Structure
Understanding amino acid structure is simpler than you think! Every amino acid has the same basic framework: an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and that all-important R group - all attached to a central carbon.
The magic happens with the R group (side chain). This is what makes each of the 20 naturally occurring amino acids unique. For example, serine has a simple -CH₂OH side chain, whilst cysteine is the only amino acid containing sulphur in its -CH₂SH group.
Leucine shows how R groups can be much larger and more complex, with its branched hydrocarbon chain. These different side chains give each amino acid distinct properties - some are polar, others non-polar, some are charged, others neutral.
Remember: The purple boxed area (amino group, carboxyl group, hydrogen, and central carbon) is identical in every amino acid - only the R group changes!
Forming Dipeptides
Here's where amino acids start becoming something bigger! When two amino acids join together through a condensation reaction, they form a dipeptide connected by a crucial peptide bond.
The process is surprisingly elegant: the hydroxyl group from one amino acid's carboxyl group combines with a hydrogen atom from another amino acid's amino group. This creates a molecule of water and leaves behind a strong covalent bond between the amino acids.
Hydrolysis does the exact opposite - it breaks apart dipeptides by adding water back in. This is how your digestive system breaks down dietary proteins into individual amino acids that your body can use.
Top tip: Remember that condensation reactions always remove water to form bonds, whilst hydrolysis reactions always add water to break bonds - this pattern appears throughout biology!
Quick Review Questions
Let's check your understanding with some straightforward questions that often appear on exams.
All amino acids contain four elements: carbon, hydrogen, oxygen, and nitrogen. The peptide bond connects amino acids together through condensation reactions that also produce water as a byproduct.
What makes amino acids unique? Their R groups create the diversity. What makes polypeptides different from each other? It's all about the sequence and number of amino acids - like having different arrangements of the same alphabet letters creating completely different words.
Exam success: These fundamental concepts appear in virtually every protein-related question, so nail these basics and you're already ahead of the game!
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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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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
Understanding Amino Acids and Polypeptides
Victor
@the1andonly
Ever wondered why your muscles can contract, your blood can carry oxygen, or your body can fight off infections? It all comes down to proteins - incredible molecular machines made from simple building blocks called amino acids that keep you... Show more
Course Introduction
This is your Biology workbook for Year 12, focusing on one of the most crucial topics you'll study this year. You're about to dive into amino acids and polypeptides - the fundamental components that make life possible at the molecular level.
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
Why Proteins Matter
Proteins are absolutely everywhere in your body, doing jobs you probably never imagined! These polymers are built from amino acid monomers and serve more functions than any other type of molecule.
Think about what's happening in your body right now: collagen is keeping your skin strong, haemoglobin is carrying oxygen through your blood, and insulin is regulating your blood sugar. Your muscles use myosin to contract, whilst antibodies patrol your bloodstream fighting infections.
Amino acids contain four essential elements: carbon, hydrogen, oxygen, and nitrogen (some also have sulphur). They're called amino acids because they have both an amino group and a carboxyl group attached to a central carbon atom, plus a variable R group that makes each one unique.
Key insight: The R group is what makes each amino acid different - it's like each amino acid's unique fingerprint that determines its properties and role in proteins.
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
Amino Acid Structure
Understanding amino acid structure is simpler than you think! Every amino acid has the same basic framework: an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and that all-important R group - all attached to a central carbon.
The magic happens with the R group (side chain). This is what makes each of the 20 naturally occurring amino acids unique. For example, serine has a simple -CH₂OH side chain, whilst cysteine is the only amino acid containing sulphur in its -CH₂SH group.
Leucine shows how R groups can be much larger and more complex, with its branched hydrocarbon chain. These different side chains give each amino acid distinct properties - some are polar, others non-polar, some are charged, others neutral.
Remember: The purple boxed area (amino group, carboxyl group, hydrogen, and central carbon) is identical in every amino acid - only the R group changes!
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Forming Dipeptides
Here's where amino acids start becoming something bigger! When two amino acids join together through a condensation reaction, they form a dipeptide connected by a crucial peptide bond.
The process is surprisingly elegant: the hydroxyl group from one amino acid's carboxyl group combines with a hydrogen atom from another amino acid's amino group. This creates a molecule of water and leaves behind a strong covalent bond between the amino acids.
Hydrolysis does the exact opposite - it breaks apart dipeptides by adding water back in. This is how your digestive system breaks down dietary proteins into individual amino acids that your body can use.
Top tip: Remember that condensation reactions always remove water to form bonds, whilst hydrolysis reactions always add water to break bonds - this pattern appears throughout biology!
Sign up to see the contentIt's free!
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Improve your grades
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Quick Review Questions
Let's check your understanding with some straightforward questions that often appear on exams.
All amino acids contain four elements: carbon, hydrogen, oxygen, and nitrogen. The peptide bond connects amino acids together through condensation reactions that also produce water as a byproduct.
What makes amino acids unique? Their R groups create the diversity. What makes polypeptides different from each other? It's all about the sequence and number of amino acids - like having different arrangements of the same alphabet letters creating completely different words.
Exam success: These fundamental concepts appear in virtually every protein-related question, so nail these basics and you're already ahead of the game!
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
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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Most popular content: Polypeptide
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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