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The Biological Molecules Unit 1 A-Level Biology AQA document is an expertly crafted, in-depth resource designed to guide A-Level Biology students through the foundational concepts of biological molecules as outlined in the AQA specification. This comprehensive guide provide...
3.1.1 Monomers and Polymers
The molecules of life all contain Carbon, Hydrogen, and Oxygen.
Carbohydrates – respiratory substrates which provide energy for
cells; also used for structure in cell membranes and cell walls in plants
Lipids – can be used as a respiratory substrate which provide energy
for cells; form a bilayer in cell membranes and make up some
hormones
Proteins – Main component of many cellular structures; form enzymes
and chemical messengers
Nucleic Acids – Form polymers (DNA and RNA), which make up the
genetic material of organisms; code for the sequence of amino acids,
which make up all proteins
All organisms use:
- The same nucleic acids as genetic material
- The same 20 amino acids to build proteins
- Lipids + Carbohydrates as energy stores and to make cell membranes
& walls
These similarities support the theory of evolution from a common
ancestor
Monomers are the smaller units from which larger molecules are
made
Polymers are molecules made from lots of repeating units
(monomers) joined together
Ionic Molecules:
A Non-Metal element bonded to a Metal element through the
transfer of electrons
,Held together by a force of attraction between the Positive and Negative
charges.
Covalent Molecules:
2 Non-Metal elements bonded through the sharing of electrons
Hydrogen Bond:
δ - Delta – Represents a small amount
Hδ+ = Slight Positive Charge
Oδ- = Slight Negative Charge
A slight force of attraction between Hδ+ and Oδ- creates a hydrogen
bond
Condensation Reaction:
Monomers are joined by removal of OH from one monomer and removal of H
from the other at the site of bond formation.
OH = Hydroxyl Group
Hydrolysis Reaction:
,Monomers are released by the addition of a water molecule, adding OH to
one molecule and H to the other.
Carbohydrates Proteins Nucleic Acids
Monomers Monosaccharides Amino Acids Nucleotides
(e.g., glucose,
fructose,
galactose)
Covalent Bond Glycosidic Bond Peptide Bond Phosphodiester
Type Bond
Polymer Made Polysaccharides Polypeptide Polynucleotide
Polymer Glycogen Enzymes DNA
Examples (Animals) Antibodies RNA
Cellulose (Plants) Channel Proteins
Starch (Plants) Haemoglobin
Polysaccharides (Sugar Polymers) are made by many monosaccharides
(Single Sugar Monomers) joined together
Disaccharides are made by two monosaccharides joined together
Isomers: Two or more compounds with the same formula, but a different
arrangement of atoms in the molecule, and therefore different properties.
A Reducing Sugar is a sugar that serves as a reducing agent (Donates
electrons to other molecules during reaction). All monosaccharides are
reducing sugars, along with some disaccharides.
A Non-Reducing Sugar is a sugar which cannot serve as a reducing agent.
An example is sucrose.
, Monosaccharides
These are the monomers that join to form disaccharides and
polysaccharides.
Examples: Glucose, Fructose, Galactose. The two sugar molecules
we encounter are hexose sugars (six carbon atoms) and pentose
sugars (five carbon atoms).
α Glucose (Alpha Glucose):
β Glucose (Beta Glucose):
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