Biological molecules

Most carbohydrates are monomers - large complex molecules composed of long chains of monomers

Monomers - small basic molecular units e.g. monosaccharides, amino acids, nucleotides

Carbohydrates are made from monosaccharides (e.g. glucose, fructose, galactose):

• contain C, H, O
• Glucose is a hexose sugar - 6 C atoms
• 2 types of glucose ( alpha and beta) theyre isomers (same molecular formula - different connection) alpha has OH below H group on right hand side <<see notes>>

Monosaccharides are joined by condensation reactions - glycosidic bond and H20 - a dissacharide is formed             OH HO becomes O and H2O

glucose + fructose = sucrose                              glucose + galactose = lactose

Reverse --> hydrolysis breaks polymers - breaks carbohydrates into monosaccharides  with H2O

Reducing sugars:

• include all monosaccharides and some disaccharides
• Add Benedicts reagent (blue) and heat
• positive will form a coloured precipitate
• blue green yellow orange brick red
• -------> higher concentration ------->
• could filter and weigh

Non Reducing sugars:

• if reducing is negative could be non reducing
• have to break into monosaccharides
• add dilute hydrochloric acid, heat
• neutralise with sodium hydrocarbonate
• then carry out Benedicts test

Polysaccharides - Loads of sugars joied together. 2+ monosaccharides joind together by a condensation reaction. e.g. a-glucose joined by glycosidic bonds to form amylose

Starch - main energy storage material in plants:

• cells get energy from glucose. Plants store glucose as starch (breaks down when needed)
• Starch is a mixture of two polysaccharides of alpha glucose:  Amylose (long branched chain, coiled structure, compact so good for storage, fit more into a small space). Amylopectin (long branched chain, side branches allow the enzymes that break down the molecule to get to the glycosidic bonds easily - glucose released quickly)
• Insoluble - doesnt affect water potential (doesnt cause osmosis into cells) good for storage

Iodine test for starch: Add iodine in potassium solution. Changes from browny orange to blue black

Glycogen - main storage material in animals:

• animals store glucose as glycogen (polysaccharide and a-glucose)
• Structure similar to amylopectin - more side branches - stored glucose can be released quickly
• compact molecule - good for storage

Cellulose - major component of cell walls in plants:

• long unbranched chains of beta-glucose
• beta-glucose molecules' bonds - form straight cellulose chains
• chains linked by hydrogen bonds to form strong fibres called microfibrils. Structural support.

(Fats and Oils)      Contain C H O

Used as: Energy store (chemical energy in tails) , Insulation, Protection (kidney), Waterproofing, Buoyancy

Insoluble - because of their tails - doesnt affect water potential of cell and cause water to enter through osmosis

Triglyceride: glycerol and three fatty acid chains (hydrocarbon, hydrophobic tails)

Glycerol's H forms ester bond with OH from carboxyl group in condensation reaction. (hydrolysis reverse)

Fatty acid chains contain carboxyll and r group <<see notes>> Saturated - no double bonds between C atoms. Unsaturated - double bonds between C atoms (monounsaturated - one C=C)

The more C=C, the more unsaturated and so the more bends - cant get as close together so liquid at room temperature

Test by adding ethanol, shaking, adding water. Cloudy white suspension means lipid (emulsion)

Made from Long chains of amino acids (monomers of proteins - 2 = dipeptide, 3+ = polypeptide) - poteins are made of one or more polypeptide

AA have a carboxyl group (-COOH), an amine group (-NH2) and an R group (variable group)<book>

Polypeptides are formed by condensation reactions - peptide bonds - <see diagram>

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