Understanding biochemistry is like having a toolkit for analysing life... Show more
Biology350 views·Updated Jun 2, 2026·2 pagesAS Level Biology 1.1: KEY Topics Explained - WJEC
Kat bert@katbert
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Biochemical Tests and Water Properties
You'll need to master four key biochemical tests for your exams. Starch turns blue-black with iodine solution, whilst proteins change from blue to purple with biuret reagent. For lipids, mix with ethanol then water - a cloudy emulsion means lipids are present.
Reducing sugars create a colour spectrum with Benedict's reagent, from blue (no sugar) through green, yellow, orange to brick-red (loads of sugar). Non-reducing sugars need boiling with hydrochloric acid first to break them down.
Water's unique properties make life possible. Its high surface tension creates habitats, whilst high specific heat capacity keeps cellular conditions stable. The fact that ice floats protects aquatic life underneath, and water's cohesive properties allow it to be pulled up through plant stems.
Quick Tip: Remember the acronym CHILIS for water properties - Colourless, High surface tension, High latent heat, High specific heat, Ice floats, Liquid at room temp, Strong cohesion!
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Protein Structure and Lipid Functions
Protein structure has four levels you must understand. Primary structure is simply the amino acid sequence, whilst secondary structure involves hydrogen bonding creating repeating patterns like alpha-helices. Tertiary structure gives the final 3D shape through various bonds and interactions.
Globular proteins fold into spherical shapes and dissolve in water (like haemoglobin), whereas fibrous proteins remain long and parallel, usually insoluble (like collagen). Quaternary structure involves multiple polypeptide chains working together.
Lipids serve three main functions: insulation, energy storage, and protection. Triglycerides combine glycerol with three fatty acids, whilst phospholipids have just two fatty acids plus a phosphate group, creating molecules with hydrophilic heads and hydrophobic tails.
Exam Focus: Van der Waals forces occur because electrons move constantly, creating temporary positive and negative areas that help molecules stick together - this often appears in extended response questions!
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Biology350 views·Updated Jun 2, 2026·2 pagesAS Level Biology 1.1: KEY Topics Explained - WJEC
Kat bert@katbert
Understanding biochemistry is like having a toolkit for analysing life itself - these fundamental tests and molecular structures form the backbone of A-level Biology. From identifying what's in your food to understanding how proteins fold, these concepts will pop up... Show more
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Biochemical Tests and Water Properties
You'll need to master four key biochemical tests for your exams. Starch turns blue-black with iodine solution, whilst proteins change from blue to purple with biuret reagent. For lipids, mix with ethanol then water - a cloudy emulsion means lipids are present.
Reducing sugars create a colour spectrum with Benedict's reagent, from blue (no sugar) through green, yellow, orange to brick-red (loads of sugar). Non-reducing sugars need boiling with hydrochloric acid first to break them down.
Water's unique properties make life possible. Its high surface tension creates habitats, whilst high specific heat capacity keeps cellular conditions stable. The fact that ice floats protects aquatic life underneath, and water's cohesive properties allow it to be pulled up through plant stems.
Quick Tip: Remember the acronym CHILIS for water properties - Colourless, High surface tension, High latent heat, High specific heat, Ice floats, Liquid at room temp, Strong cohesion!
2
of 2Sign up to see the content. It's free!
- Access to all documents
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Protein Structure and Lipid Functions
Protein structure has four levels you must understand. Primary structure is simply the amino acid sequence, whilst secondary structure involves hydrogen bonding creating repeating patterns like alpha-helices. Tertiary structure gives the final 3D shape through various bonds and interactions.
Globular proteins fold into spherical shapes and dissolve in water (like haemoglobin), whereas fibrous proteins remain long and parallel, usually insoluble (like collagen). Quaternary structure involves multiple polypeptide chains working together.
Lipids serve three main functions: insulation, energy storage, and protection. Triglycerides combine glycerol with three fatty acids, whilst phospholipids have just two fatty acids plus a phosphate group, creating molecules with hydrophilic heads and hydrophobic tails.
Exam Focus: Van der Waals forces occur because electrons move constantly, creating temporary positive and negative areas that help molecules stick together - this often appears in extended response questions!
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.
Similar content
Most popular content: Proteins
5Most popular content in Biology
9Most popular content
9Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google 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 SiOS 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 KlichAndroid 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.
AnnaiOS user