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AS Biology
Biological Molecules:

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· Definition: a group of substances used as energy sources
and are made up of carbon, hydrogen and oxygen
· General formula: Cx(H2O)y
· Functions:
­ Energy source ­ respiration
­ Energy store ­ starch
­ Structure ­ cellulose
· Main groups:
­ Monosaccharides ­ simple monomers; contain 3 to 6 carbon
atoms; soluble in waters; sweet tasting; form crystals
­ Disaccharides - double sugars formed by a condensation
reaction (2 monosaccharides joined together);
­ Polysaccharides ­ large molecules formed from many
monosaccharides (e.g. Starch, glycogen, cellulose)…read more

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· Monosaccharide - Hexose sugar
· General formula: C6H12O6
· Characteristics:
­ Energy source for cells
­ highly soluble & sweet
­ Crystalline
· Structural isomers of glucose:
­ Alpha glucose ­ the OH group is below the
­ Beta glucose ­ the OH group is above the
carbon…read more

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· Respiration
­ Glucose is broken down into water & CO2 to make ATP
­ Each step involves a specific enzyme
­ Animals and plants can only break -glucose and not -glucose
because of the different arrangement of the H and OH at carbon 1
· Amylose: condensation reaction with thousands of glucose
molecules bonded
­ 1-4 glycosidic bond
­ Long chains coil into springs due to shape of molecules and bonds
­ makes it compact
­ Iodine molecules get trapped in coils causing colour change ­
yellow/brown to blue/black
­ These large molecules are not water soluble…read more

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Energy storage
Starch Glycogen
Consists of long, straight-chain Made up of alpha-glucose subunits
amylose molecules & branched Large molecule that can be broken
amylopectin down to be respired
Stored in chloroplasts of plants & Animals store glucose as glycogen
membrane-bound starch grains
Amylose has a compact, coiled Very compact so it is good for storage.
structure ­ good for fitting more in
Amylopectin branches allow enzymes Has many side branches so stored
to break down glucose to release glucose can be released quickly,
energy (respiration) which is important in animals
Insoluble in water. Makes them useful
for storage…read more

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· Definition: a carbohydrate polymer made by
bonding many beta-glucose molecules
together in long, unbranched chains.
· Structural polysaccharide found only in plants.
· Cellulose chains are linked by hydrogen bonds
to form strong microfibrils. Provides structural
support for cells.…read more

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