Source: https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-2-proteins-a2-only

[Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [A Level](https://senecalearning.com/en-gb/revision-notes/a-level.md) › [Chemistry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry.md) › [AQA](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa.md) › Proteins (A2 Only)

# Proteins (A2 Only)

Chemistry: AQA A Level, topic 6.7.2

## Proteins

Amino acids are the monomers that form proteins. Proteins are important biological molecules with complex 3D structures.

### Synthesis

![Synthesis](https://image-v2.cdn.app.senecalearning.com/2018-08/08c77efc-ccdf-47d5-bb87-e3898cf07d8f/Dipeptide.jpg)

- Amino acids undergo condensation reactions to form proteins.
 - The carboxylic acid and amine groups can react to form a peptide linkage (biological word for amide linkage).
 - Two amino acid groups will react to form a dipeptide. Three amino acid groups will form a tripeptide and so on.

### Primary structure

![Primary structure](https://image-v2.cdn.app.senecalearning.com/2018-08/9f665841-8ed1-4713-baae-4bf94f7f33cf/polypeptide.jpg)

- The primary structure is given by the sequence of amino acids.
- The primary structure is held together by strong covalent bonds with peptide linkages happening between amino acid units.   
- In biology notation, each amino acid is represented by a three letter code. For example, alanine is Ala.

### Secondary structure

![Secondary structure](https://image-v2.cdn.app.senecalearning.com/2018-08/af35e42f-6270-41fd-a99a-98707db5e73b/DNA-double-helix-.jpg)

- The secondary structure is a result of the arrangement of polypeptide chains which causes specific hydrogen bonding interactions and lead to a specific secondary structure.
 - There are two types of secondary structure.
- The first is the α-helix:
 - α-Helix is a regular coiled configuration held together by hydrogen bonding. The chain twists into a coiled helix shape.

### Secondary structure

![Secondary structure](https://image-v2.cdn.app.senecalearning.com/2018-09/5f0c8a39-ad59-4b62-b80a-6264188cefea/beta-pleated-sheet-protein-secondary-structure-.png)

- The second secondary structure is β-pleated sheets:
 - β-pleated sheets cause amino acid sequences to run parallel to one another and extend to give a structure with pleated sheets.

### Tertiary structure

![Tertiary structure](https://image-v2.cdn.app.senecalearning.com/2018-09/e0e02c7c-784b-492e-8e10-a09138e54120/ribosome-protein-.jpg)

- The helices and sheets in the secondary structure can fold and interact to order the polypeptide strands into the final shape of the protein.
- The complex 3-D shape is stabilised by the following interactions of the amino acid side chains: 
 - Disulfide bridges (covalent S-S bonds).
 - Weak van der Waals’ forces.
 - Hydrogen bonding.
 - Ionic bonds.

## Enzymes

One of the most important functions of proteins is their use as enzymes. Enzymes are biological catalysts, which are highly specific.

### Specificity

![Specificity](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.2.1%20-%20Enzymes%201/key-2114046_640-min.jpg)

- Enzymes are made specific by their selective active sites.
- They are so specific that they can even select between stereoisomers such that they will only bind to one enantiomer of a substrate.
 - An example is L-amino oxidase, which only works on the L-amino acid and not the other enantiomer, the D-amino acid.

### Enzyme action

![Enzyme action](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/2.2.2%20Enzyme%20action%20-synthesis%20(s).png)

- A simple representation of enzyme action is the lock-and-key mechanism. 
 - This shows a simple representation of the importance of the shape of the active site. 
 - Because enzymes are proteins, this shape is determined by the 3D structure of the protein.

### Drugs as inhibitors

![Drugs as inhibitors](https://image-v2.cdn.app.senecalearning.com/2018-04/21e836e2-d655-42a0-9bc5-ccf5b5dbfd27/shutterstock_556414345.jpg)

- Enzymes can be deactivated using drugs.
 - The drug molecule can also bind to the active site.
- The level of inhibition is dependant on:
 - The relative concentration of substrate and drugs.
 - The relative binding strength of the drug and the substrate.

### Using computers to design drugs

![Using computers to design drugs](https://image-v2.cdn.app.senecalearning.com/2018-08/6cd86383-5aae-448b-acdb-2a8748168832/keyboard-70506_1920.jpg)

- If we know the structure of the enzyme and its active site, chemists can use computer modelling to find new drugs that would fit into the active site.
- The modelling calculates whether or not molecules have the correct polarity and stereochemistry to fit into the active site.
- The proposed models are then synthesised and their structure is optimised by experimental work.

## Test yourself on Proteins (A2 Only)

- What makes enzymes so selective?
- Computers can model drugs. What two features must drugs have to "fit" into an active site?

[Practise this topic for free](https://app.senecalearning.com/classroom/course/89dad2dd-9f68-460c-9247-131aea534bdb/section/76dfc141-2e61-4312-96d6-08361f136e6a/session)

- Previous topic: [6.7.1 Amino Acids (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-1-amino-acids-a2-only.md)
- Next topic: [6.7.3 DNA (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-3-dna-a2-only.md)

## Chemistry: AQA A Level contents

### 1 Physical Chemistry
- 1.1 Atomic Structure
  - [1.1.1 Fundamental Particles](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-1-fundamental-particles.md)
  - [1.1.2 Isotopes & Mass Number](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-2-isotopes-and-mass-number.md)
  - [1.1.3 Mass Spectrometry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-3-mass-spectrometry.md)
  - [1.1.4 Electron Shells, Sub-Shells & Orbitals](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-4-electron-shells-sub-shells-and-orbitals.md)
  - [1.1.5 Electron Configuration](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-5-electron-configuration.md)
  - [1.1.6 Ionisation Energy](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-6-ionisation-energy.md)
  - [1.1.7 Factors Affecting Ionisation Energies](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-7-factors-affecting-ionisation-energies.md)
  - [1.1.8 Trends of Ionisation](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-8-trends-of-ionisation.md)
  - [1.1.9 Specific Impacts on Ionisation Energies](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-9-specific-impacts-on-ionisation-energies.md)
  - [1.1.10 End of Topic Test - Atomic Structure](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-10-end-of-topic-test-atomic-structure.md)
  - [1.1.11 A-A* (AO3/4) - Atomic Structure](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-1-11-a-a-ao34-atomic-structure.md)
- 1.2 Amount of Substance
  - [1.2.1 Relative Masses](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-1-relative-masses.md)
  - [1.2.2 The Mole](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-2-the-mole.md)
  - [1.2.3 The Ideal Gas Equation](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-3-the-ideal-gas-equation.md)
  - [1.2.4 Empirical & Molecular Formulae](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-4-empirical-and-molecular-formulae.md)
  - [1.2.5 Balanced Equations](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-5-balanced-equations.md)
  - [1.2.6 Percentage Yield](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-6-percentage-yield.md)
  - [1.2.7 A-A* (AO3/4) - Percentage Yield](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-7-a-a-ao34-percentage-yield.md)
  - [1.2.8 Atom Economy](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-8-atom-economy.md)
  - [1.2.9 End of Topic Test - Amount of Substance](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-9-end-of-topic-test-amount-of-substance.md)
  - [1.2.10 A-A* (AO3/4) - Substances & Yield](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-10-a-a-ao34-substances-and-yield.md)
  - [1.2.11 Diagnostic Misconceptions - Moles](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-2-11-diagnostic-misconceptions-moles.md)
- 1.3 Bonding
  - [1.3.1 Ionic Bonding](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-1-ionic-bonding.md)
  - [1.3.2 Covalent & Dative Bonding](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-2-covalent-and-dative-bonding.md)
  - [1.3.3 Carbon Structures](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-3-carbon-structures.md)
  - [1.3.4 Metallic Bonding](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-4-metallic-bonding.md)
  - [1.3.5 Physical Properties](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-5-physical-properties.md)
  - [1.3.6 Shapes of Molecules](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-6-shapes-of-molecules.md)
  - [1.3.7 Polarity](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-7-polarity.md)
  - [1.3.8 Intermolecular Forces](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-8-intermolecular-forces.md)
  - [1.3.9 Intermolecular Forces 2](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-9-intermolecular-forces-2.md)
  - [1.3.10 End of Topic Test - Bonding](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-10-end-of-topic-test-bonding.md)
  - [1.3.11 Exam-Style Question - Shape of Molecules](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-11-exam-style-question-shape-of-molecules.md)
  - [1.3.12 A-A* (AO3/4) - Bonding](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-12-a-a-ao34-bonding.md)
  - [1.3.13 Diagnostic Misconceptions - Ions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-13-diagnostic-misconceptions-ions.md)
  - [1.3.14 Diagnostic Misconceptions - Ionic & Covalent](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-14-diagnostic-misconceptions-ionic-and-covalent.md)
  - [1.3.15 Diagnostic Misconceptions - Phase Change](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-15-diagnostic-misconceptions-phase-change.md)
  - [1.3.16 Diagnostic Misconceptions - Boiling](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-16-diagnostic-misconceptions-boiling.md)
  - [1.3.17 Diagnostic Misconceptions - Polar Bonds](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-3-17-diagnostic-misconceptions-polar-bonds.md)
- 1.4 Energetics
  - [1.4.1 Enthalpy Changes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-1-enthalpy-changes.md)
  - [1.4.2 Bond Breaking and Making](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-2-bond-breaking-and-making.md)
  - [1.4.3 Enthalpy Changes: Standard Conditions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-3-enthalpy-changes-standard-conditions.md)
  - [1.4.4 Calorimetry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-4-calorimetry.md)
  - [1.4.5 Hess' Law](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-5-hess-law.md)
  - [1.4.6 Bond Enthalpies](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-6-bond-enthalpies.md)
  - [1.4.7 End of Topic Test - Energetics](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-7-end-of-topic-test-energetics.md)
  - [1.4.8 Diagnostic Misconceptions - Calorimetry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-4-8-diagnostic-misconceptions-calorimetry.md)
- 1.5 Kinetics
  - [1.5.1 Collision Theory](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-5-1-collision-theory.md)
  - [1.5.2 Maxwell-Boltzmann Distribution](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-5-2-maxwell-boltzmann-distribution.md)
  - [1.5.3 Increasing Rates](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-5-3-increasing-rates.md)
  - [1.5.4 End of Topic Test - Kinetics](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-5-4-end-of-topic-test-kinetics.md)
- 1.6 Equilibria
  - [1.6.1 Le Chatelier](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-6-1-le-chatelier.md)
  - [1.6.2 Equilibrium Constants](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-6-2-equilibrium-constants.md)
  - [1.6.3 A-A* (AO3/4) - Energetics, Kinetics, Equilibria](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-6-3-a-a-ao34-energetics-kinetics-equilibria.md)
  - [1.6.4 End of Topic Test - Equilibria](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-6-4-end-of-topic-test-equilibria.md)
  - [1.6.5 Diagnostic Misconceptions - Solids](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-6-5-diagnostic-misconceptions-solids.md)
- 1.7 Redox
  - [1.7.1 Redox](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-7-1-redox.md)
  - [1.7.2 End of Topic Test - Redox](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/1-7-2-end-of-topic-test-redox.md)

### 2 Physical Chemistry 2 (A2 Only)
- 2.1 Thermodynamics (A2 Only)
  - [2.1.1 Born-Haber Cycles (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-1-born-haber-cycles-a2-only.md)
  - [2.1.2 Born-Haber Cycle Calculations (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-2-born-haber-cycle-calculations-a2-only.md)
  - [2.1.3 Entropy (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-3-entropy-a2-only.md)
  - [2.1.4 Free Energy (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-4-free-energy-a2-only.md)
  - [2.1.5 End of Topic Test - Thermodynamics](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-5-end-of-topic-test-thermodynamics.md)
  - [2.1.6 A-A* (AO3/4) - Thermodynamics](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-1-6-a-a-ao34-thermodynamics.md)
- 2.2 Rate Equations (A2 Only)
  - [2.2.1 Rate Equations (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-1-rate-equations-a2-only.md)
  - [2.2.2 Rate Equations 2 (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-2-rate-equations-2-a2-only.md)
  - [2.2.3 The Arrhenius Equation (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-3-the-arrhenius-equation-a2-only.md)
  - [2.2.4 Experimental Methods for Rates (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-4-experimental-methods-for-rates-a2-only.md)
  - [2.2.5 End of Topic Test - Rate Equations](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-5-end-of-topic-test-rate-equations.md)
  - [2.2.6 Exam-Style Question - Rates](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-6-exam-style-question-rates.md)
  - [2.2.7 A-A* (AO3/4) - Rate Equations](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-2-7-a-a-ao34-rate-equations.md)
- 2.3 The Equilibrium Constant Kp (A2 Only)
  - [2.3.1 Properties of Kp (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-3-1-properties-of-kp-a2-only.md)
- 2.4 Electrochemical Cells (A2 Only)
  - [2.4.1 Electrochemical Cells (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-1-electrochemical-cells-a2-only.md)
  - [2.4.2 Electrochemical Series (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-2-electrochemical-series-a2-only.md)
  - [2.4.3 Commercial Application (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-3-commercial-application-a2-only.md)
  - [2.4.4 End of Topic Test - Kp & Electrochemistry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-4-end-of-topic-test-kp-and-electrochemistry.md)
  - [2.4.5 A-A* (AO3/4) - Electrochemical Cells](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-5-a-a-ao34-electrochemical-cells.md)
  - [2.4.6 Diagnostic Misconceptions - Salt Bridges](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-6-diagnostic-misconceptions-salt-bridges.md)
  - [2.4.7 Diagnostic Misconceptions - Electrode, Electrolyte](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-4-7-diagnostic-misconceptions-electrode-electrolyte.md)
- 2.5 Acids & Bases (A2 Only)
  - [2.5.1 Brønsted-Lowry Acids & Bases (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-1-bronsted-lowry-acids-and-bases-a2-only.md)
  - [2.5.2 pH (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-2-ph-a2-only.md)
  - [2.5.3 The Ionic Product of Water (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-3-the-ionic-product-of-water-a2-only.md)
  - [2.5.4 Weak Acids & Bases (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-4-weak-acids-and-bases-a2-only.md)
  - [2.5.5 pH Curves & Titrations (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-5-ph-curves-and-titrations-a2-only.md)
  - [2.5.6 pH Curves & Titrations 2 (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-6-ph-curves-and-titrations-2-a2-only.md)
  - [2.5.7 Buffer Solutions (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-7-buffer-solutions-a2-only.md)
  - [2.5.8 End of Topic Test - Acids & Bases](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-8-end-of-topic-test-acids-and-bases.md)
  - [2.5.9 Exam-Style Question - Weak Acids](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-9-exam-style-question-weak-acids.md)
  - [2.5.10 A-A* (AO3/4) - Acids & Bases](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-10-a-a-ao34-acids-and-bases.md)
  - [2.5.11 Diagnostic Misconceptions - Ammonia is an Alkali](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-11-diagnostic-misconceptions-ammonia-is-an-alkali.md)
  - [2.5.12 Diagnostic Misconceptions - Water's Neutrality](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-12-diagnostic-misconceptions-waters-neutrality.md)
  - [2.5.13 Diagnostic Misconceptions - Concentrate & Strength](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/2-5-13-diagnostic-misconceptions-concentrate-and-strength.md)

### 3 Inorganic Chemistry
- 3.1 Periodicity & Trends
  - [3.1.1 The Periodic Table](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-1-1-the-periodic-table.md)
  - [3.1.2 Trends in the Periodic Table](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-1-2-trends-in-the-periodic-table.md)
  - [3.1.3 End of Topic Test - Periodicity & Trends](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-1-3-end-of-topic-test-periodicity-and-trends.md)
  - [3.1.4 Diagnostic Misconceptions - Atomic Radius](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-1-4-diagnostic-misconceptions-atomic-radius.md)
- 3.2 Group 2
  - [3.2.1 Group 2 Chemistry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-2-1-group-2-chemistry.md)
  - [3.2.2 End of Topic Test - Group 2](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-2-2-end-of-topic-test-group-2.md)
- 3.3 Group 7
  - [3.3.1 Introduction to Halogens](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-1-introduction-to-halogens.md)
  - [3.3.2 Reactions of Halogens](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-2-reactions-of-halogens.md)
  - [3.3.3 Chlorine & Chlorate(I)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-3-chlorine-and-chloratei.md)
  - [3.3.4 End of Topic Test - Group 7](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-4-end-of-topic-test-group-7.md)
  - [3.3.5 Exam-Style Question - Group 7](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-5-exam-style-question-group-7.md)
  - [3.3.6 A-A* (AO3/4) - Periodicity, Group 2 & 7](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/3-3-6-a-a-ao34-periodicity-group-2-and-7.md)

### 4 Inorganic Chemistry 2 (A2 Only)
- 4.1 Period 3 (A2 Only)
  - [4.1.1 Period 3 Elements & Oxides (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-1-1-period-3-elements-and-oxides-a2-only.md)
  - [4.1.2 Period 3 Oxides (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-1-2-period-3-oxides-a2-only.md)
  - [4.1.3 End of Topic Test - Period 3](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-1-3-end-of-topic-test-period-3.md)
- 4.2 Transition Metals (A2 Only)
  - [4.2.1 General Properties (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-1-general-properties-a2-only.md)
  - [4.2.2 Substitution Reactions (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-2-substitution-reactions-a2-only.md)
  - [4.2.3 Shapes of Complex Ions (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-3-shapes-of-complex-ions-a2-only.md)
  - [4.2.4 Colours of Ions (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-4-colours-of-ions-a2-only.md)
  - [4.2.5 Variable Oxidation States (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-5-variable-oxidation-states-a2-only.md)
  - [4.2.6 Titrations (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-6-titrations-a2-only.md)
  - [4.2.7 Homogeneous Catalysts (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-7-homogeneous-catalysts-a2-only.md)
  - [4.2.8 Heterogeneous Catalysts (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-8-heterogeneous-catalysts-a2-only.md)
  - [4.2.9 End of Topic Test - Transition Metals](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-9-end-of-topic-test-transition-metals.md)
  - [4.2.10 A-A* (AO3/4) - Transition Metals](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-2-10-a-a-ao34-transition-metals.md)
- 4.3 Reactions of Ions in Aqueous Solutions (A2 Only)
  - [4.3.1 Acidity (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-3-1-acidity-a2-only.md)
  - [4.3.2 Identification (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-3-2-identification-a2-only.md)
  - [4.3.3 End of Topic Test - Reactions of Ions in Solution](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/4-3-3-end-of-topic-test-reactions-of-ions-in-solution.md)

### 5 Organic Chemistry 1
- 5.1 Introduction
  - [5.1.1 Naming Conventions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-1-1-naming-conventions.md)
  - [5.1.2 Mechanism](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-1-2-mechanism.md)
  - [5.1.3 Isomerism](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-1-3-isomerism.md)
  - [5.1.4 End of Topic Test - Introduction to Organic Chem](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-1-4-end-of-topic-test-introduction-to-organic-chem.md)
- 5.2 Alkanes
  - [5.2.1 Fractional Distillation](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-2-1-fractional-distillation.md)
  - [5.2.2 Cracking](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-2-2-cracking.md)
  - [5.2.3 Combustion](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-2-3-combustion.md)
  - [5.2.4 Chlorination](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-2-4-chlorination.md)
  - [5.2.5 End of Topic Test - Alkanes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-2-5-end-of-topic-test-alkanes.md)
- 5.3 Halogenoalkanes
  - [5.3.1 Substitution Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-3-1-substitution-reactions.md)
  - [5.3.2 Elimination Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-3-2-elimination-reactions.md)
  - [5.3.3 Ozone Depletion](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-3-3-ozone-depletion.md)
  - [5.3.4 End of Topic Test - Halogenoalkanes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-3-4-end-of-topic-test-halogenoalkanes.md)
- 5.4 Alkenes
  - [5.4.1 Introduction to Alkenes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-4-1-introduction-to-alkenes.md)
  - [5.4.2 Reactions of Alkenes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-4-2-reactions-of-alkenes.md)
  - [5.4.3 Polymerisation Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-4-3-polymerisation-reactions.md)
  - [5.4.4 Properties of Polymers](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-4-4-properties-of-polymers.md)
  - [5.4.5 End of Topic Test - Alkenes](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-4-5-end-of-topic-test-alkenes.md)
- 5.5 Alcohols
  - [5.5.1 Production of Alcohols](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-1-production-of-alcohols.md)
  - [5.5.2 Oxidation of Alcohols](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-2-oxidation-of-alcohols.md)
  - [5.5.3 Oxidation of Alcohols - 2](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-3-oxidation-of-alcohols-2.md)
  - [5.5.4 Elimination Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-4-elimination-reactions.md)
  - [5.5.5 End of Topic Test - Alcohols](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-5-end-of-topic-test-alcohols.md)
  - [5.5.6 Exam-Style Question - Alcohols](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-5-6-exam-style-question-alcohols.md)
- 5.6 Organic Analysis
  - [5.6.1 Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-6-1-reactions.md)
  - [5.6.2 Reactions 2](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-6-2-reactions-2.md)
  - [5.6.3 Mass Spectrometry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-6-3-mass-spectrometry.md)
  - [5.6.4 Infrared Spectroscopy](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-6-4-infrared-spectroscopy.md)
  - [5.6.5 End of Topic Test - Organic Analysis](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-6-5-end-of-topic-test-organic-analysis.md)
- 5.7 A-A* (AO3/4) - Organic 1
  - [5.7.1 A-A* (AO3/4) - Organic 1](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/5-7-1-a-a-ao34-organic-1.md)

### 6 Organic Chemistry 2 (A2 Only)
- 6.1 Optical Isomerism (A2 Only)
  - [6.1.1 Optical Isomerism (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-1-1-optical-isomerism-a2-only.md)
  - [6.1.2 End of Topic Test - Optical Isomerism](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-1-2-end-of-topic-test-optical-isomerism.md)
- 6.2 Aldehydes & Ketones (A2 Only)
  - [6.2.1 Aldehydes & Ketones (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-2-1-aldehydes-and-ketones-a2-only.md)
  - [6.2.2 End of Topic Test - Aldehydes & Ketones](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-2-2-end-of-topic-test-aldehydes-and-ketones.md)
- 6.3 Carboxylic Acids & Esters (A2 Only)
  - [6.3.1 Acids & Esters (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-3-1-acids-and-esters-a2-only.md)
  - [6.3.2 Acylation (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-3-2-acylation-a2-only.md)
  - [6.3.3 End of Topic Test - Carboxylic Acids & Esters](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-3-3-end-of-topic-test-carboxylic-acids-and-esters.md)
- 6.4 Aromatic Chemistry (A2 Only)
  - [6.4.1 Structure & Reactivity (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-4-1-structure-and-reactivity-a2-only.md)
  - [6.4.2 Reactions of Benzene (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-4-2-reactions-of-benzene-a2-only.md)
  - [6.4.3 End of Topic Test - Aromatic Chemistry](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-4-3-end-of-topic-test-aromatic-chemistry.md)
- 6.5 Amines (A2 Only)
  - [6.5.1 Nature & Preparation of Amines (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-5-1-nature-and-preparation-of-amines-a2-only.md)
  - [6.5.2 Basicity & Nucleophilicity (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-5-2-basicity-and-nucleophilicity-a2-only.md)
  - [6.5.3 End of Topic Test - Amines](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-5-3-end-of-topic-test-amines.md)
- 6.6 Polymers (A2 Only)
  - [6.6.1 Condensation Polymers (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-6-1-condensation-polymers-a2-only.md)
  - [6.6.2 Biodegradability (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-6-2-biodegradability-a2-only.md)
- 6.7 Biological Organic (A2 Only)
  - [6.7.1 Amino Acids (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-1-amino-acids-a2-only.md)
  - [6.7.2 Proteins (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-2-proteins-a2-only.md)
  - [6.7.3 DNA (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-3-dna-a2-only.md)
  - [6.7.4 Anti-Cancer Drugs (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-4-anti-cancer-drugs-a2-only.md)
  - [6.7.5 End of Topic Test - Biological Organic](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-7-5-end-of-topic-test-biological-organic.md)
- 6.8 Organic Synthesis (A2 Only)
  - [6.8.1 Organic Synthesis (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-8-1-organic-synthesis-a2-only.md)
  - [6.8.2 Examples of Synthetic Routes (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-8-2-examples-of-synthetic-routes-a2-only.md)
  - [6.8.3 End of Topic Test - Polymers & Organic Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-8-3-end-of-topic-test-polymers-and-organic-synthesis.md)
- 6.9 NMR Spectroscopy (A2 Only)
  - [6.9.1 Understanding NMR (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-9-1-understanding-nmr-a2-only.md)
  - [6.9.2 Carbon-13 NMR (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-9-2-carbon-13-nmr-a2-only.md)
  - [6.9.3 Hydrogen-1 NMR (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-9-3-hydrogen-1-nmr-a2-only.md)
  - [6.9.4 Hydrogen-1 NMR 2 (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-9-4-hydrogen-1-nmr-2-a2-only.md)
  - [6.9.5 End of Topic Test - NMR](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-9-5-end-of-topic-test-nmr.md)
- 6.10 Chromatography (A2 Only)
  - [6.10.1 Overview of Chromatography (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-10-1-overview-of-chromatography-a2-only.md)
  - [6.10.2 Thin-Layer Chromatography (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-10-2-thin-layer-chromatography-a2-only.md)
  - [6.10.3 Column Chromatography (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-10-3-column-chromatography-a2-only.md)
  - [6.10.4 Gas Chromatography (A2 Only)](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-10-4-gas-chromatography-a2-only.md)
  - [6.10.5 End of Topic Test - Chromatography](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-10-5-end-of-topic-test-chromatography.md)
- 6.11 A-A* (AO3/4) - Organic 2
  - [6.11.1 A-A* (AO3/4) - Organic 2](https://senecalearning.com/en-gb/revision-notes/a-level/chemistry/aqa/6-11-1-a-a-ao34-organic-2.md)