Subjects
Maths
Chemistry
Biology
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
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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
3 Dec 2025
988
3 pages
Niamh Cooke @niamhcooke_yelp
Biological molecules are the building blocks of all living things, from the water in your cells to the... Show more
Ever wondered why you need to drink water to survive? Water is a polar molecule with an unequal charge distribution - hydrogen atoms are slightly positive whilst oxygen is slightly negative. This simple property makes water absolutely essential for life.
Water acts as the perfect solvent for metabolic reactions and has a high specific heat capacity, which means it takes loads of energy to heat up. This is brilliant for your body because it prevents dangerous temperature swings. When you sweat, water's large latent heat creates a cooling effect as it evaporates.
The strong cohesion between water molecules enables plants to transport water up through their stems - imagine tiny water molecules holding hands in an unbreakable chain! Ice floats because it's less dense than liquid water, creating an insulating layer that protects aquatic life in winter.
Inorganic ions like hydrogen (controls blood pH), iron (found in haemoglobin), sodium (helps transport glucose), and phosphates (essential for DNA and ATP) occur throughout your body in varying concentrations. You can test for different biological molecules using simple food tests - Benedict's for sugars, Biuret for proteins, emulsion test for lipids, and iodine for starch.
Quick Tip Remember food test colours - Benedict's turns red for positive, Biuret goes lilac, emulsion test becomes cloudy, and iodine turns blue-black with starch!
Proteins literally build and run your body - from the enzymes digesting your food to the haemoglobin carrying oxygen in your blood. Amino acids are protein monomers containing an amine group, carboxylic acid group, and a variable 'R' group that makes each of the 20 amino acids unique.
Primary structure refers to the specific order of amino acids in the chain. This sequence determines everything else about the protein's function. Secondary structure describes how the chain folds into either alpha helixes or beta pleated sheets, held together by hydrogen bonds.
The tertiary structure is the final 3D shape - either globular (compact and rounded like enzymes) or fibrous (long and thin like keratin in your hair). This shape determines the protein's job completely.
Collagen demonstrates fibrous proteins perfectly - its incredible strength comes from hydrogen and covalent bonds, with molecules wrapping around each other to form tough fibrils in your tendons and skin. Haemoglobin shows globular proteins in action - its four polypeptide chains each contain a haem group that grabs oxygen molecules and releases them where needed.
Memory Hack Think of protein structure like building a house - primary is choosing the bricks (amino acid order), secondary is making walls , and tertiary is the final building shape!
Carbohydrates are your body's preferred fuel source, made entirely of carbon, hydrogen, and oxygen atoms. They range from simple monosaccharides like glucose to complex polysaccharides that store massive amounts of energy.
Glucose exists as alpha or beta forms - this tiny difference matters hugely! Glycogen (your body's energy store) uses alpha glucose with 1,4 and 1,6 glycosidic bonds creating loads of branches for quick energy release. Starch stores plant energy through amylose (unbranched, coiled) and amylopectin (branched). Meanwhile, cellulose uses beta glucose to create incredibly strong plant cell walls.
Lipids are only soluble in organic solvents like alcohol, not water. Saturated fats have no carbon-carbon double bonds and stay solid at room temperature, whilst unsaturated fats contain double bonds that create kinks, keeping them liquid.
Triglycerides store energy efficiently - one glycerol molecule plus three fatty acid chains joined by ester bonds. Phospholipids replace one fatty acid with a hydrophilic phosphate group, creating molecules that love and hate water simultaneously. This dual nature makes them perfect for cell membranes, forming protective barriers with hydrophilic heads facing outward and hydrophobic tails tucked inside.
Key Insight The shape of molecules determines their function - branched glycogen releases energy quickly, whilst unbranched cellulose creates structural strength!
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.
24
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Comprehensive A-Level Biology notes covering essential biological molecules including carbohydrates (starch, glycogen, cellulose), proteins (amino acids, structure), lipids, and enzymes. Understand monomers, polymers, and the role of enzymes in biochemical reactions. Ideal for exam preparation and revision.
BiologyExplore comprehensive revision notes on biological molecules, including carbohydrates, lipids, proteins, and nucleic acids. Understand key concepts such as enzyme-substrate complexes, DNA replication, and the properties of ATP. Ideal for AS/A Level Biology students preparing for exams.
Biologysimplified notes for quick recall
BiologyExplore the essential concepts of biological molecules, including the roles of water, monomers, and polymers. This summary covers carbohydrates, their types (monosaccharides, disaccharides, polysaccharides), and key processes like condensation and hydrolysis. Ideal for biology students seeking to grasp the fundamentals of biomolecules and their significance in metabolic reactions.
BiologyExplore the essential concepts of biological molecules, including carbohydrates, proteins, and lipids. This summary covers the structure and function of key macromolecules, condensation and hydrolysis reactions, and the role of hydrogen bonds in biological systems. Ideal for students preparing for exams or seeking a comprehensive understanding of biomolecules.
BiologyExplore the fundamentals of metabolism, including its definition, examples like respiration, and the metabolic rate. This summary covers the three main types of food molecules: carbohydrates, proteins, and lipids, essential for GCSE Biology students. Enhance your understanding of cellular processes and energy usage in living organisms.
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
Niamh Cooke
@niamhcooke_yelp
Biological molecules are the building blocks of all living things, from the water in your cells to the proteins that make your muscles work. Understanding these molecules - water, carbohydrates, lipids, and proteins - helps explain how your body functions... 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 why you need to drink water to survive? Water is a polar molecule with an unequal charge distribution - hydrogen atoms are slightly positive whilst oxygen is slightly negative. This simple property makes water absolutely essential for life.
Water acts as the perfect solvent for metabolic reactions and has a high specific heat capacity, which means it takes loads of energy to heat up. This is brilliant for your body because it prevents dangerous temperature swings. When you sweat, water's large latent heat creates a cooling effect as it evaporates.
The strong cohesion between water molecules enables plants to transport water up through their stems - imagine tiny water molecules holding hands in an unbreakable chain! Ice floats because it's less dense than liquid water, creating an insulating layer that protects aquatic life in winter.
Inorganic ions like hydrogen (controls blood pH), iron (found in haemoglobin), sodium (helps transport glucose), and phosphates (essential for DNA and ATP) occur throughout your body in varying concentrations. You can test for different biological molecules using simple food tests - Benedict's for sugars, Biuret for proteins, emulsion test for lipids, and iodine for starch.
Quick Tip: Remember food test colours - Benedict's turns red for positive, Biuret goes lilac, emulsion test becomes cloudy, and iodine turns blue-black with starch!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Proteins literally build and run your body - from the enzymes digesting your food to the haemoglobin carrying oxygen in your blood. Amino acids are protein monomers containing an amine group, carboxylic acid group, and a variable 'R' group that makes each of the 20 amino acids unique.
Primary structure refers to the specific order of amino acids in the chain. This sequence determines everything else about the protein's function. Secondary structure describes how the chain folds into either alpha helixes or beta pleated sheets, held together by hydrogen bonds.
The tertiary structure is the final 3D shape - either globular (compact and rounded like enzymes) or fibrous (long and thin like keratin in your hair). This shape determines the protein's job completely.
Collagen demonstrates fibrous proteins perfectly - its incredible strength comes from hydrogen and covalent bonds, with molecules wrapping around each other to form tough fibrils in your tendons and skin. Haemoglobin shows globular proteins in action - its four polypeptide chains each contain a haem group that grabs oxygen molecules and releases them where needed.
Memory Hack: Think of protein structure like building a house - primary is choosing the bricks (amino acid order), secondary is making walls , and tertiary is the final building shape!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Carbohydrates are your body's preferred fuel source, made entirely of carbon, hydrogen, and oxygen atoms. They range from simple monosaccharides like glucose to complex polysaccharides that store massive amounts of energy.
Glucose exists as alpha or beta forms - this tiny difference matters hugely! Glycogen (your body's energy store) uses alpha glucose with 1,4 and 1,6 glycosidic bonds creating loads of branches for quick energy release. Starch stores plant energy through amylose (unbranched, coiled) and amylopectin (branched). Meanwhile, cellulose uses beta glucose to create incredibly strong plant cell walls.
Lipids are only soluble in organic solvents like alcohol, not water. Saturated fats have no carbon-carbon double bonds and stay solid at room temperature, whilst unsaturated fats contain double bonds that create kinks, keeping them liquid.
Triglycerides store energy efficiently - one glycerol molecule plus three fatty acid chains joined by ester bonds. Phospholipids replace one fatty acid with a hydrophilic phosphate group, creating molecules that love and hate water simultaneously. This dual nature makes them perfect for cell membranes, forming protective barriers with hydrophilic heads facing outward and hydrophobic tails tucked inside.
Key Insight: The shape of molecules determines their function - branched glycogen releases energy quickly, whilst unbranched cellulose creates structural strength!
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.
24
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Comprehensive A-Level Biology notes covering essential biological molecules including carbohydrates (starch, glycogen, cellulose), proteins (amino acids, structure), lipids, and enzymes. Understand monomers, polymers, and the role of enzymes in biochemical reactions. Ideal for exam preparation and revision.
BiologyExplore comprehensive revision notes on biological molecules, including carbohydrates, lipids, proteins, and nucleic acids. Understand key concepts such as enzyme-substrate complexes, DNA replication, and the properties of ATP. Ideal for AS/A Level Biology students preparing for exams.
Biologysimplified notes for quick recall
BiologyExplore the essential concepts of biological molecules, including the roles of water, monomers, and polymers. This summary covers carbohydrates, their types (monosaccharides, disaccharides, polysaccharides), and key processes like condensation and hydrolysis. Ideal for biology students seeking to grasp the fundamentals of biomolecules and their significance in metabolic reactions.
BiologyExplore the essential concepts of biological molecules, including carbohydrates, proteins, and lipids. This summary covers the structure and function of key macromolecules, condensation and hydrolysis reactions, and the role of hydrogen bonds in biological systems. Ideal for students preparing for exams or seeking a comprehensive understanding of biomolecules.
BiologyExplore the fundamentals of metabolism, including its definition, examples like respiration, and the metabolic rate. This summary covers the three main types of food molecules: carbohydrates, proteins, and lipids, essential for GCSE Biology students. Enhance your understanding of cellular processes and energy usage in living organisms.
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
Sociology