Maths
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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
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Chemistry
2 Dec 2025
117
3 pages
Ever wondered how the proteins in your muscles are built, or why some medicines work differently on different... Show more
Amino acids are the building blocks of proteins, and they're pretty clever molecules because they contain both an amine group (NH₂) and a carboxyl group (COOH). This dual personality makes them incredibly versatile in chemical reactions.
Think of amino acids as chemical chameleons. The COOH group can act as an acid (donating protons), whilst the NH₂ group can act as a base (accepting protons). This means amino acids can react with both acids and bases to form salts.
For example, when 2-aminoethanoic acid reacts with sodium hydroxide (NaOH), the carboxyl group loses a proton. When it reacts with hydrochloric acid (HCl), the amine group gains a proton. This ability to react with both acids and bases is what makes amino acids so important in biological systems.
Quick Tip Remember that amino acids are amphoteric - they can behave as both acids and bases depending on the conditions!
The carboxyl group in amino acids can also undergo esterification when reacted with alcohols under acidic conditions. This reaction produces an ester and water, just like other carboxylic acid reactions you've seen before.
Now, let's tackle isomers - molecules that share the same molecular formula but differ in other ways. Structural isomers have different structural formulas entirely, like completely different arrangements of atoms.
Stereoisomers are more subtle - they have the same molecular and structural formulas but different spatial arrangements. This includes E/Z isomers, which exist around C=C double bonds where rotation is restricted, and optical isomers, which are non-superimposable mirror images.
Remember For E/Z isomers to exist, each carbon in the C=C bond must be connected to two different substituents - no rotation allowed!
Optical isomers are like your left and right hands - they're mirror images that can't be superimposed on each other, no matter how you twist them. This happens when you have a chiral carbon atom bonded to four different groups.
The chiral carbon adopts a tetrahedral shape with bond angles of 109.5°. Each chiral carbon produces exactly two optical isomers, called a pair of enantiomers. These molecules are identical in most properties but rotate light in opposite directions.
It's crucial to remember that carbons involved in double bonds or benzene rings can't be chiral because they don't have four different substituents. Many amino acids contain chiral carbons, which is why this concept is so important in biochemistry.
Key Point Look for carbons bonded to four different groups - that's your chiral centre and the source of optical isomerism!
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.
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Explore the fundamentals of hydrocarbons, including their classification into aliphatic, alicyclic, and aromatic types. This summary covers key concepts such as homologous series, functional groups, and the general formulas for alkanes, alkenes, and alkynes. Ideal for OCR A A-Level Chemistry students seeking a concise understanding of organic chemistry.
ChemistryExplore the fundamentals of isomerism in organic chemistry, including structural isomers, position isomers, and functional group isomers. Understand the impact of molecular structure on physical properties, and learn the rules for naming carbon chains using IUPAC nomenclature. This summary covers key concepts such as stereochemistry, intermolecular forces, and the characteristics of alkanes, alkenes, and carboxylic acids.
ChemistryExplore key concepts in organic chemistry, including nomenclature, reaction mechanisms, and isomerism. This summary covers IUPAC naming rules, functional groups, and stereochemistry, providing a comprehensive overview for AQA AS Organic Chemistry students.
ChemistryExplore the structural characteristics and bonding of benzene, including the comparison between the Kekulé and delocalized models. This summary covers key concepts such as resonance, sigma bonds, and the implications of enthalpy changes in hydrogenation. Ideal for OCR A-Level Chemistry students seeking to understand the stability and reactivity of benzene and its derivatives.
ChemistryHope this helps!
ChemistryExplore the key concepts of hydrocarbons in National 5 Chemistry, including alkanes, alkenes, cycloalkanes, and isomerism. This summary covers the structural differences, properties, and general formulas of these compounds, providing a clear understanding of their roles in organic chemistry.
ChemistryApp 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
Ever wondered how the proteins in your muscles are built, or why some medicines work differently on different people? It all comes down to amino acids and their fascinating chemical properties, including their ability to exist as mirror images of... Show more
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Amino acids are the building blocks of proteins, and they're pretty clever molecules because they contain both an amine group (NH₂) and a carboxyl group (COOH). This dual personality makes them incredibly versatile in chemical reactions.
Think of amino acids as chemical chameleons. The COOH group can act as an acid (donating protons), whilst the NH₂ group can act as a base (accepting protons). This means amino acids can react with both acids and bases to form salts.
For example, when 2-aminoethanoic acid reacts with sodium hydroxide (NaOH), the carboxyl group loses a proton. When it reacts with hydrochloric acid (HCl), the amine group gains a proton. This ability to react with both acids and bases is what makes amino acids so important in biological systems.
Quick Tip: Remember that amino acids are amphoteric - they can behave as both acids and bases depending on the conditions!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The carboxyl group in amino acids can also undergo esterification when reacted with alcohols under acidic conditions. This reaction produces an ester and water, just like other carboxylic acid reactions you've seen before.
Now, let's tackle isomers - molecules that share the same molecular formula but differ in other ways. Structural isomers have different structural formulas entirely, like completely different arrangements of atoms.
Stereoisomers are more subtle - they have the same molecular and structural formulas but different spatial arrangements. This includes E/Z isomers, which exist around C=C double bonds where rotation is restricted, and optical isomers, which are non-superimposable mirror images.
Remember: For E/Z isomers to exist, each carbon in the C=C bond must be connected to two different substituents - no rotation allowed!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Optical isomers are like your left and right hands - they're mirror images that can't be superimposed on each other, no matter how you twist them. This happens when you have a chiral carbon atom bonded to four different groups.
The chiral carbon adopts a tetrahedral shape with bond angles of 109.5°. Each chiral carbon produces exactly two optical isomers, called a pair of enantiomers. These molecules are identical in most properties but rotate light in opposite directions.
It's crucial to remember that carbons involved in double bonds or benzene rings can't be chiral because they don't have four different substituents. Many amino acids contain chiral carbons, which is why this concept is so important in biochemistry.
Key Point: Look for carbons bonded to four different groups - that's your chiral centre and the source of optical isomerism!
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.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamentals of hydrocarbons, including their classification into aliphatic, alicyclic, and aromatic types. This summary covers key concepts such as homologous series, functional groups, and the general formulas for alkanes, alkenes, and alkynes. Ideal for OCR A A-Level Chemistry students seeking a concise understanding of organic chemistry.
ChemistryExplore the fundamentals of isomerism in organic chemistry, including structural isomers, position isomers, and functional group isomers. Understand the impact of molecular structure on physical properties, and learn the rules for naming carbon chains using IUPAC nomenclature. This summary covers key concepts such as stereochemistry, intermolecular forces, and the characteristics of alkanes, alkenes, and carboxylic acids.
ChemistryExplore key concepts in organic chemistry, including nomenclature, reaction mechanisms, and isomerism. This summary covers IUPAC naming rules, functional groups, and stereochemistry, providing a comprehensive overview for AQA AS Organic Chemistry students.
ChemistryExplore the structural characteristics and bonding of benzene, including the comparison between the Kekulé and delocalized models. This summary covers key concepts such as resonance, sigma bonds, and the implications of enthalpy changes in hydrogenation. Ideal for OCR A-Level Chemistry students seeking to understand the stability and reactivity of benzene and its derivatives.
ChemistryHope this helps!
ChemistryExplore the key concepts of hydrocarbons in National 5 Chemistry, including alkanes, alkenes, cycloalkanes, and isomerism. This summary covers the structural differences, properties, and general formulas of these compounds, providing a clear understanding of their roles in organic chemistry.
ChemistryApp 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
