H2 Biology - Notes on Biomolecules

Notes on biomolecules (CARBOHYDRATES) Carbohydrate (Cx(H2O)y) Monosaccharides  Sweet, crystalline in nature  Soluble in water  All reducing sugar due to presence of carbonyl group  C6H12O6

Major classes Glucose

Structure

Functions

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Fructose

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Disaccharides  Sweet, crystalline  Hydrolysed easily into monosacchari des by adding water

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Example of aldose sugar (C=O group at the end) Exist in open chain form and stable ring structure 1 C react with oxygen atom on 5C to form 6sided ring Isomers o Alpha glucose (OH same side) o Beta glucose (OH opposite sides) Example of ketone sugar (C=O in the middle of the chain) 2 C reacts with oxygen on 5C to form 5-sided ring Formed by polymerization reaction called condensation 1 water molecule eliminated

Maltose

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Glucose + glucose -> maltose + water

Lactose

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Glucose + galactose -> lactose + water

Sucrose

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Glucose + fructose -> sucrose + water α (1->2)β glyco bond Non-reducing as no free carbonyl group as carbonyl groups are used in the bond between C-1 of glucose and C-2 of fructose Polymer of several hundreds of alpha glucose Made up of amylose

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Respiratory substrates Raw materials for synthesis of other carbohydrates Exert osmotic pressure

Polysaccharides Starch   (C6H10O5)n  Not sugar => no sweet  1|Page Created by SefLRho (2012) DHS

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Breakdown product during digestion of starch by enzymes Brewing of beer Found in milk (energy source for young mammals) Storage sugar in plants o Very soluble and relatively unreactive chemically

Stores large amt of energy Compact and ideal for storage

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Do not exert osmostic pressure Glycosidic bonds easily hydrolyzed by conc. Acid/enzymes

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Glycogen

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Cellulose

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and amylopectin  Amylopectin easily (amylopectin > amylase) hydrolysed by 70-80% : 30% debranching enzymes Amylose a(1->4)  Insoluble, therefore glycosidic bond osmotically inactive o Unbranched Enzymes that target starch straight chain  α amylase (cleave o Coil helically randomly) due to intra H  β amylase (cleave from bond between the ends) C2 and C3  Debranching (cleave at o OH groups 1->6 bonds projected into the interior o Responsible for the blueblack colouration in iodine test Amylopectin a(1->6) glycosidic bond and a(1>4) glycosidic bond o Highly branched and compact o Gives red-violet colour wit iodine in KI Branched chain of a  Storage polysaccharide glucose in animals. Favoured form of energy store Structure similar to because it does not amylopectin but has exert osmotic pressure greater branching that and can be prevented amylopectin from diffusing out of Hydroxyl group the cell projected inwards and  Energy stored in C-H thus no cross-linking => bonds easily hydrolyzed to monosaccharides when  Readily converted to required glucose by enzyme action (glucagon) Made up beta glucose  Structural support forming linear,  Great tensile strength unbranched chain  Form cell walls (prevent b(1->4) glycosidic bonds cell from bursting by unbranched linear endo-osmosis chains lie parallel to  Fully permeable and each other does not restrict solute cross-linking H bonds movement between chains  Most organisms do not chains associate into have enzymes to digest groups to form cellulose and therefore microfibrils cellulose produce fibers

2|Page Created by SefLRho (2012) DHS

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microfibrils twisted into large bundles to form macrofibrils β glycosidic bonds requires a rotation in a space of 180o of alternating sugar residues

for peristalsis

Food tests for carbohydrates o BENEDICTS: test for reducing sugar  Prepare water bath, add Benedict reagent, heat 5 min (no more, if not possibility of false positive results)  Results (quantitative) Blue