Ever wonder how your muscles work or what makes enzymes... 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
5
0
Lucy
04/12/2025
Biology
AQA A Level Biology Proteins notes
412
•
4 Dec 2025
•
Comprehensive AQA A Level Biology Proteins Study Notes
Lucy
@lucy_sldh
1 / 3
Building Blocks of Life: Amino Acids and Protein Formation
Think of amino acids as biological Lego blocks - there are 20 different types, and they can be arranged in countless ways to create different proteins. Each amino acid has the same basic structure: an amine group (NH2), a carboxyl group (COOH), and a unique side chain (R group) that gives it special properties.
When two amino acids join together through a condensation reaction, they form a peptide bond by releasing a water molecule. Two amino acids create a dipeptide, whilst many amino acids linked together form a polypeptide.
The brilliant thing is that amino acids can be arranged in any sequence you can imagine. Since proteins can be hundreds of amino acids long, the possibilities are virtually endless! This sequence isn't random though - it's precisely this order that determines how the protein will fold and ultimately how it'll function in your body.
Key Point: The sequence of amino acids is like a recipe - change the order, and you get a completely different protein with different abilities!
The Four Levels of Protein Structure
Understanding protein structure is like understanding architecture - there are four distinct levels that build upon each other. The primary structure is simply the sequence of amino acids in the chain, like letters in a sentence.
The secondary structure forms when the chain starts to fold into regular patterns. The two main types are the alpha helix (like a spiral staircase) and the beta pleated sheet (like a folded fan). These shapes are held together by hydrogen bonds - weak but important chemical attractions between different parts of the chain.
Some proteins go further and develop a tertiary structure, where the entire chain folds into a complex 3D shape. This is especially important for enzymes! When the protein has a roughly spherical shape, we call it a globular protein. Finally, quaternary structure occurs when multiple polypeptide chains work together as one functional unit.
Remember: Each level of structure depends on the one before it - mess up the primary structure, and everything else goes wrong too!
Quick Review: Key Protein Concepts
Let's nail down the essentials you need to remember for your exams. The primary structure is the specific order of amino acids in a protein chain - think of it as the protein's unique fingerprint.
Hydrogen bonds are the weak forces that hold the secondary structure together, creating those characteristic helixes and pleated sheets. Meanwhile, peptide bonds form between amino acids during condensation reactions, creating the backbone of every protein.
Here's the big picture: a protein's structure determines its function, and that structure is entirely decided by the sequence of amino acids. Change even one amino acid, and you might completely alter what the protein can do.
Exam Tip: Remember the hierarchy - primary determines secondary, secondary influences tertiary, and some proteins need quaternary structure to work properly!
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.
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
Comprehensive AQA A Level Biology Proteins Study Notes
Lucy
@lucy_sldh
Ever wonder how your muscles work or what makes enzymes so special? It all comes down to proteins - these incredible molecules that do most of the heavy lifting in your body. Understanding how proteins are built from simple building... Show more
Building Blocks of Life: Amino Acids and Protein Formation
Think of amino acids as biological Lego blocks - there are 20 different types, and they can be arranged in countless ways to create different proteins. Each amino acid has the same basic structure: an amine group (NH2), a carboxyl group (COOH), and a unique side chain (R group) that gives it special properties.
When two amino acids join together through a condensation reaction, they form a peptide bond by releasing a water molecule. Two amino acids create a dipeptide, whilst many amino acids linked together form a polypeptide.
The brilliant thing is that amino acids can be arranged in any sequence you can imagine. Since proteins can be hundreds of amino acids long, the possibilities are virtually endless! This sequence isn't random though - it's precisely this order that determines how the protein will fold and ultimately how it'll function in your body.
Key Point: The sequence of amino acids is like a recipe - change the order, and you get a completely different protein with different abilities!
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
The Four Levels of Protein Structure
Understanding protein structure is like understanding architecture - there are four distinct levels that build upon each other. The primary structure is simply the sequence of amino acids in the chain, like letters in a sentence.
The secondary structure forms when the chain starts to fold into regular patterns. The two main types are the alpha helix (like a spiral staircase) and the beta pleated sheet (like a folded fan). These shapes are held together by hydrogen bonds - weak but important chemical attractions between different parts of the chain.
Some proteins go further and develop a tertiary structure, where the entire chain folds into a complex 3D shape. This is especially important for enzymes! When the protein has a roughly spherical shape, we call it a globular protein. Finally, quaternary structure occurs when multiple polypeptide chains work together as one functional unit.
Remember: Each level of structure depends on the one before it - mess up the primary structure, and everything else goes wrong too!
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
Quick Review: Key Protein Concepts
Let's nail down the essentials you need to remember for your exams. The primary structure is the specific order of amino acids in a protein chain - think of it as the protein's unique fingerprint.
Hydrogen bonds are the weak forces that hold the secondary structure together, creating those characteristic helixes and pleated sheets. Meanwhile, peptide bonds form between amino acids during condensation reactions, creating the backbone of every protein.
Here's the big picture: a protein's structure determines its function, and that structure is entirely decided by the sequence of amino acids. Change even one amino acid, and you might completely alter what the protein can do.
Exam Tip: Remember the hierarchy - primary determines secondary, secondary influences tertiary, and some proteins need quaternary structure to work properly!
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.
5
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Similar content
Protein Structure Overview
Explore the essential concepts of protein structure, including amino acids, peptide bonds, and the four levels of protein organization. This summary covers key topics such as the primary, secondary, tertiary, and quaternary structures, along with examples like collagen and hemoglobin. Ideal for AQA A-Level Biology students seeking a comprehensive understanding of protein functions and structures.
Biology12
A-Level Biology Active Recall
Enhance your understanding of A-Level OCR Biology with this comprehensive active recall resource. Covering key concepts such as cell structure, enzyme function, and ecological interactions, this study material is designed to reinforce your knowledge and improve exam performance. Ideal for revision and self-assessment.
Biology12
Biological molecules - proteins
OCR a level biology
Biology13
Digestive Enzymes Overview
Explore the essential roles of digestive enzymes in breaking down proteins, fats, and carbohydrates. This summary covers the functions of lipases, proteases, and amylase, detailing their sources and the digestion process. Ideal for biology students seeking to understand nutrient absorption and enzyme activity.
Biology11
Digestive Enzymes Explained
Explore the role of digestive enzymes in breaking down food molecules into absorbable nutrients. This summary covers key concepts such as the lock-and-key model, enzyme specificity, and the functions of protease, lipase, and carbohydrase in digestion. Ideal for biology students preparing for exams.
Biology11
Triglycerides & Phospholipids Overview
Explore the formation and functions of triglycerides and phospholipids, including ester bonds, energy storage, and membrane structure. This summary covers key concepts such as cholesterol's role in membrane fluidity and the hydrophilic and hydrophobic properties of lipids. Ideal for students studying lipid biochemistry.
Biology12
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