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AQA A level Biology Unit 1 Biological Molecules Summary Notes

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Detailed notes following the spec points Consists of : Unit 1 - Biological Molecules Unit 2 - Cells Unit 3 - Organisms Exchange Substances with their Environment Unit 4 - Genetic Information, Variation and Relationships between Organisms

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1.1 MONOMERS AND POLYMERS
MONOMERS – smaller units that make up a large molecule (eg)
-​ Monosaccharides (fructose, galactose, glucose)
-​ Nucleotides
-​ amino acids
-​ ribose, deoxyribose
➢​ CONDENSATION reaction joins two molecules/monomers together to form any chemical
bonds by removing one water molecule ​
○​ Glycosidic bonds = monosaccharides
○​ Peptide = amino acids
○​ Ester = glycerol and fatty acid
○​ phosphodiester bonds = nucleotides
➢​ HYDROLYSIS breaks a chemical bond between 2 molecules/monomers with a water
molecule

POLYMERS – long chain molecules made from many monomer units joined together
-​ DNA, RNA,
-​ Polysaccharides (amylose, cellulose, starch, glycogen)
-​ Proteins (polypeptides)


1.2 CARBOHYDRATES
MONOSACCHARIDES – monomers that make up long chain polysaccharides/ large carbohydrates
DISACCHARIDES – formed from condensation of 2 monosaccharides, forms a GLYCOSIDIC
BOND (1,4 or 1,6) and removing a water molecule
POLYSACCHARIDES – long chain made from many, depends on its monosaccharides

3 COMMON HEXOSE MONOSACCHARIDES (C6H12O6 = hexose )
-​ Glucose (alpha or beta)
-​ Fructose
-​ Galactose
Monosaccharides Disaccharides Polysaccharides




Glucose + glucose = Maltose (helps digestion of starch) -​ Starch (amylose
and amylopectin)
Glucose + fructose = Sucrose (plant sugar, non reducing) -​ Cellulose
-​ Glycogen
Glucose + galactose = Lactose (milk sugar)

PROPERTIES

-​ Soluble -​ Soluble -​ Insoluble
-​ Small enough to pass -​ Large = Too big to pass -​ Large = Too big
through partially -​ Sweet to pass
permeable membranes -​ Not sweet
-​ Sweet

, ISOMERS OF GLUCOSE – ALPHA + BETA same molecular formula, different structural formula/
arranged differently




★​ Removing a H2O molecule, forming a
glycosidic bond
★​ BETA GLUCOSE FLIP ONE SIDE
★​ (1,4) = normal
★​ (1,6) = branched




POLYSACCHARIDES PROPERTIES + FUNCTION (x3 plant, x1 animal)

CELLULOSE ➢​ Beta Glucose (only one out of 4)
➢​ (1,4) glycosidic bonds = Unbranched

➢​ Straight, long parallel chains = forms H-bonds with parallel chains
= forms microfibrils = support and strengthen cell wall to prevent cell
bursting so it stays turgid

➢​ Alternating chain


AMYLOSE ➢​ Alpha glucose
(starch) = storage ➢​ (1,4) glycosidic bonds = unbranced

➢​ Helical, coiled structure form H-bonds = compact for long term storage
➢​ Insoluble + Large = no osmotic effect and does not diffuse out the cell
so starch stays in cell (all insoluble except cellulose)

Connected book
 image
Glenn Toole, Susan Toole AQA Biology A Level Student Book
Publisher: april 2015 ISBN: 9780198351771 Edition: 1

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Unit 1
Uploaded on
August 22, 2025
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2024/2025
Type
Summary
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