I created these notes throughout y12&13 and used them for my A level 2022 exams. I got a grade 9 in GCSE and am awaiting for my a level biology result. These notes were made using the CGP revision guide, AQA Biology textbook and class notes in order to cover everything in the course. I have also ad...
1.1 INTRODUCTION TO BIOLOGICAL
MOLECULES
07 September 2020
18:25
Covalent bonding - Atoms share a pair of electrons in their outer shells.
● Outer shells of both atoms are filled. A stable molecule is formed.
Ionic bonding - Electrostatic force of attraction between Ions with opposite charges
attract one another.
● Weaker thanks to covalent bonds.
Hydrogen bonding - Electrons within a molecule may not be evenly distributed.
● These are polar molecules.
● The negative region of one molecule and the positive region of another
attract.
- Forming a weak electrostatic force of attraction.
● The bonds can collectively form important forces, altering physical properties
of molecules.
Polymers - Molecules made from many monomers joined together.
Monomers - The smaller units from which larger, polymer molecules are made.
● Amino acids, monosaccharides, nucleotides.
The process by which polymers are formed is polymerisation.
Each time a sub-unit is attached a water molecule is formed.
Condensation reaction - Joins two molecules together with the formation of a
chemical bond and involves the elimination of a molecule of water.
Polymers can be broken down by the addition of water.
Hydrolysis reaction - Breaks a chemical bond between two molecules and involves
the use of a water molecule.
Metabolism - All the chemical processes that take place in living organisms or cells.
1.2 CARBOHYDRATES - MONOSACCHARIDES
,25 November 2020
12:03
Monosaccharides are the monomers from which larger carbohydrates are made of.
● Glucose, fructose and galactose.
The basic monomer unit in carbohydrates is a sugar.
● Monosaccharides - One single sugar unit.
2 Monosaccharides can join to form disaccharides.
● 2 sugar units joined together.
Many monosaccharides can join to form large polysaccharides by condensation
reactions.
● Many sugar units joined together.
● Used for storage and structure.
Monosaccharides are small, sweet and soluble crystals.
They have a general formula of (CH2O)n.
● n is any number from 3-7.
Hexose sugars have 6 carbon atoms.
They all have the chemical formula C6H12O6, but have different structures.
● Isomers.
Glucose has 2 isomers:
-α-glucose.
● Has the H on the top of the first carbon atom, and the OH group on the
bottom of the first carbon atom.
-β-glucose.
● Has the OH group on the top of the first carbon atom, and the H on the
bottom of the first carbon atom.
, All monosaccharides and some disaccharides like maltose and lactose are reducing
sugars.
Reduction is a reaction involving the gain of electrons.
Reducing sugars can donate electrons to other molecules, reducing them.
Benedict's reagent is used in the benedict's test for reducing sugars.
● Benedict's reagent is an alkaline solution of copper(II) sulfate.
● When heated with equal volume of sugar solution, the
● The
- This is an insoluble brick red precipitate.
The test is semi-quantitative, giving a rough idea of the amount of reducing sugar in
the sample.
● Add 2 cm of solution into a clean test tube.
● Add an equal volume of benedict's reagent.
● Heat the test tube in a water bath for 5 minutes.
● If there is no reducing sugar present, the solution remains blue.
● If there is a certain amount of reducing sugar in the sample:
- Green - There's a very small amount.
- Yellow - There's a low amount.
- Orange - A medium amount.
- Brick red - A high amount.
● The higher the concentration, the further the colour change goes.
A more accurate measurement of the amount of reducing sugar is to use a
colorimeter.
A more accurate way of comparing the amount of reducing sugar is to filter the
solution using filter paper.
● Then weigh the precipitate.
1.3 CARBOHYDRATES - DISACCHARIDES AND
POLYSACCHARIDES
04 December 2020
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