Summary
Summary WJEC (Wales) Unit 1.1 Carbohydrates notes
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Notes written for examination of WJEC (Wales) AS level Biology Unit 1
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CarbohydratesFeatures:
Contain C,H,O
= hydrated carbon
General formula: CnH2nOn
3 types:
1. Monosaccharide
Monomers
= sugars ∵sweet, soluble in water, form crystals at normal temp
Type Exist as Example Uses
Triose C3H6O3 Straight chains Glyceraldehyde Intermediate molecule in respiration
Pentose C5H10H5 Ring structures Deoxyribose Make DNA
Ribose Make RNA & ATP
Hexose C6H12O6 Ring structures Glucose Energy source in respiration
Galactose Milk sugar
Fructose Sweetens fruits
Glucose (C6H12O6)
Contain aldehyde group (-CHO) / ketone group (C=O)
Isomers result in different biological properties when formed polymers
Types: (ABBA – α below, β above)
a. α-glucose b. β-glucose
-> form starch -> form cellulose
Functions (monosaccharides):
As source of energy in respiration – break C-C, C-H bonds -> transfer into ATP
Building blocks form larger molecules
Intermediates in rxns e.g. triose in respiration
Constituents of nucleotides e.g. deoxyribose in DNA
2. Disaccharides (C12H22O11)
= 2 monosaccharide, are also sugars
Undergone condensation rxn, eliminate water -> form α-1,4-glycosidic bond
Hydrolysis = chemical insertion of water molecule in order to break a bond
Maltose rxn
, Types:
Disaccharide Monosaccharide 1 Monosaccharide 2 Uses
Maltose α-glucose α-glucose Seed formation in plants
Sucrose α-glucose Fructose Transport sugar around
(5-member ring) a plant
Lactose α-glucose Galactose In mammalian milk
3. Polysaccharides [ (C6H10O5)n ]
Formed by polymerisation – bonding many monomers by condensation rxns to form 1 large
molecule
Often folded & branched
Not sugars
Large ∴cannot diffuse out of cells
Highly folded form compact molecules -> stored in small spaces
Functions:
Energy/glucose storage
Structural support
Has no osmotic effect -> prevent inc. solute potential in cells
Function types:
(a) Energy/glucose storage (in C-H/C-C bonds)
Starch
Energy source of plants & component of food of animals
Mixture of polysaccharides bonded tgt
e.g. seeds, storage organs
Gd energy store
∵ Insoluble – no osmotic effect
Compact – many can be stored in a small space
Amylose Amylopectin
Structure long, linear, unbranched chain of long-branched chain of α-glucose
α-glucose
wound tightly in coiled shape,
compact & gd to store
Energy not gd for releasing energy side branches allow enzymes to be
releasing ∵2 ends for rxn only broken down to get to the glycosidic
ability bond
Bonds form α-1,4-glycosidic bond α-1,4-glycosidic bond in main chain
repeated, form chain which coils α-1,6-glycosidic bonds between
into α helix branches
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