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Summary AQA A Level Biology Year 1 Revision Guide, ISBN: 9780198351788 Unit 1 - Biological molecules
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3.1. Biological Molecules (Mrs Robinson)3.1.1 Monomers and Polymers
Molecular Biology = study of molecules
Biochemistry = study of how molecules behave
Key elements found in the living organisms: C, H, O, P, S
Plus: Ca, Fe, Zn, Mg, Na, Cl, often as ions
Covalent bonding = atoms share a pair of electrons in their outer shells as a
result both become more stable and a molecule is formed.
Ionic bonding = ions with opposite charges have electrostatic attraction known
as an ionic bond which is weaker than a covalent bonding.
Hydrogen bonding = The electrons within a molecule are not even distributed
so one side of a molecule is negatively charged. This is said to be polarised.
The opposite charges attract one another, and a weak electrostatic bond is
formed. They are weak.
Monomer = single unit or simplest unit of a molecule that can be joined
together to form a larger molecule (polymer)
e.g. 1 Glucose = monomers
(monosaccharide)
2 Glucose = disaccharide
(Maltose)
2+ Glucose = polysaccharide
(starch, glycogen, cellulose)
Condensation reaction = joins two molecules together with the formation of a
chemical bond and involves the elimination of a mole of water.
,Hydrolysis reaction = breaks a chemical bond between two molecules and
involves the use of a water molecules
Metabolism = All the chemical process that take place in organisms (sum of all
reactions).
Mole = SI unit for measuring the amount of a substance
Molar solution = Is a solution that contains one mole of solute in each litre of
solution.
e.g. NaCl solution – 23 for Na and 35.5 for Cl = 58.5g for every litre
Polynucleotides = DNA/RNA
Monomers
Polymers (not lipids or water)
,3.1.2 Carbohydrates
Glucose and galactose are both monosaccharides
Monosaccharides – monomers (basic units) of carbohydrates
– soluble in water
– sweet tasting
– General formula (CH2O)n or Cx(H2O)y
e.g. 3 Carbon = triose sugar e.g. glyceraldehyde
5 Carbon = pentose sugar e.g. deoxyribose (in DNA)
Ribose (RNA)
6 Carbon = hexose sugar e.g. glucose, galactose, fructose
Draw alpha and beta but identify
fructose and galactose
, Glucose – energy source
– highly soluble
Alpha and beta glucose are structural isomers – the difference is the position
of the –OH group attached to carbon 1.
Alpha – energy storage starch and glycogen
Beta – cellulose for structural
Fructose and galactose – very soluble and main sugar in fruits
– galactose is not as soluble and is important in the
production of glycolipids and glycoproteins
Glycolipids and glycoproteins are found on the cell surface membrane
attached to the phospholipid or integral proteins. They are used in cell
communication and recognition.
Pentoses – contain 5 carbon atoms
– ribose and deoxyribose both are important molecules
Ribose – has an oxygen on carbon 2 and deoxy does not
Reducing sugar – donates electrons to benedict solution
Benedict’s solution is alkaline copper (ii) sulphate
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