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AQA AS-Level Biology Revision Notes - New Spec

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AQA AS-Level Biology Revision Notes - New SpecStructure of Cellulose?  β-glucose arranged in a straight chain (each alternative β-glucose is rotated 180 degrees) = cellulose straight chain � ... � many cellulose chains are cross linked by hydrogen bonds to form microfibrils  many microfibrils are cross linked to form marcrofibrils  forms structure of cell wall  strong material (prevents plant cell from bursting or shrinking) Test for starch? add iodine, turns blue/black Test for reducing sugar? heat with benedicts, turns brick red Test for non-reducing sugar?  heat with benedicts – no change  therefore, add dilute hydrochloric acid (hydrolyses glycosidic bond)  then add sodium hydrogencarbonate (neutralises solution)  heat with benedict - turns brick red What are 2 types of proteins? Globular and Fibrous What are globular proteins? soluble proteins with a specific 3D shape e.g. enzymes, hormones, antibodies, haemoglobin What are fibrous proteins? strong/insoluble/inflexible material e.g. collagen and keratin What are the building blocks for proteins? amino acids Structure of amino acid? central carbon, carboxyl group to the right (COOH), amine group to the left (NH2), hydrogen above and R group below How do amino acids differ? have different R groups e.g. glycine has a hydrogen in its R group – simplest amino acid How are amino acids joined together? by condensation reaction between the carboxyl group of one and amine group of another, leaves a bond between carbon & nitrogen (called a peptide bond) forming a dipeptide [Show More]

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