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Proteins Maintenance of structures Proper functioning of all living organisms
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Biological functions of proteins Enzymes- Catalyze biological processes e.g. Pepsin Hormones - Regulate body processes e.g. Insulin Storage proteins - Store nutrients e.g. Ferritin Transport proteins - Transport oxygen and other substances through the body e.g. Haemoglobin Structural proteins - Form an organism’s structure e.g. Collagen Protective proteins - Help fight infection e.g. Antibodies Contractile proteins - Form muscles e.g. Actin and myosin
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Structure of Proteins The building units of proteins are called amino acids All naturally occurring amino acids are -amino acids
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Most proteins are formed from some twenty common amino acids, linked up by peptide bonds Peptide linkage
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Hydrolysis of proteins Separation of amino acids by paper chromatography Linked with 1. Phase equilibrium - Application of partition 2. Chemistry of amino acids
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Carbohydrates As a source of energy Glycogen in animals, Starch in plants General formula C x H 2y O y Synthesized by photosynthesis 6CO 2 (g) + 6H 2 O(l) C 6 H 12 O 6 (s) + 6O 2 (g) light chlorophyll
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Classification of Carbohydrates Monosaccharides - (CH 2 O) n where n>2 E.g. C 6 H 12 O 6 Hexose (most important) C 5 H 10 O 5 Pentose Aldohexose Glucose Ketohexose Fructose 1 2
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Disaccharides Polysaccharides - C 12 H 22 O 11 E.g. Maltose, Sucrose - (C 6 H 10 O 5 ) n where n is a very large number E.g. Starch, Cellulose
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Open chain and cyclic structures of glucose and fructose ++.. (Fischer projection) 1 5 6 1 5 6 -glucose -glucose 5 1
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The cyclic structures are more stable than the open chain structure The lone pair on -OH can attack the carbonyl carbon from above or below the plane leading to the formation of two isomers ( and glucose).
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Fructose.. 5 ++ 2 6 1 1 2 5 6 -furanose -pyranose 1 2 6
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In the free state, fructose exists as pyranose (6-membered ring). In disaccharides and polysaccharides, fructose exists as furanose (5-membered ring).
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Disaccharides and Glycosidic linkage 2C 6 H 12 O 6 Condensation C 12 H 22 O 11 + H 2 O hydrolysis Glucose + Glucose Maltose + water Glucose + Fructose Sucrose + water
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+ 1 4 1,4-glycosidic linkage Maltose -glucose
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2 52 5 Rotate 180 o -fructose
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-glucose + -fructose 1 1 2 1 2 1,2-glycosidic linkage Sucrose
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Testing for reducing sugars Reducing sugars - sugars that contain free aldehyde group Give red ppt of Cu 2 O when treated with Fehling’s solution Complex ion of Cu 2+ + RCHOCu 2 O(s) Deep blueRed
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All monosaccharides are reducing sugars ++.. (Fischer projection) 1 5 6 1 5 6 -glucose -glucose 5 1 ~0.02% ~64%~36%
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Fructose Glucose Fructose undergoes transformation to give glucose Fructose is a reducing sugar
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Maltose 1 5 The right ring is able to open to give a free aldehyde group which can be oxidized A reducing sugar
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-glucose + -fructose 1 1 2 1 2 1,2-glycosidic linkage Sucrose Both rings are locked non-reducing sugar
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Polysaccharides nC 6 H 12 O 6 -glucose Starch nC 6 H 12 O 6 -glucose Cellulose
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Starch Amylose Amylopectin Amylose - consists of unbranched chains of -glucose units joined by -1,4 linkages Amylopectin - consists of highly branched chains of -glucose units linked by -1,4 linkages
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Amylose 1,4 glycosidic linkages
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1 6 1 6 Amylopectin 1,6-glycosidic linkages
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Cellulose : - consists of unbranched chains of -glucose units joined by 1,4-glycosidic linkages the structural component of cell walls of plant
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1 4 41 4 1 1,4 - glycosidic linkages The 2nd unit is flipped over
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Hydrolysis of Sucrose C 11 H 22 O 11 + H 2 OC 6 H 12 O 6 + C 6 H 12 O 6 H + or invertase glucosefructosesucrose [ ] D = +66. 5 o [ ] D = +52.7 o [ ] D = -92.4 o The reaction mixture undergoes an inversion in optical activity (from + to -) Laevorotatory (-) Dextrorotatory(+)
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maltase C 12 H 22 O 11 + H 2 O2C 6 H 12 O 6 Glucose 2(C 6 H 10 O 5 ) n + nH 2 O amylase nC 12 H 22 O 11 Maltose Starch (C 6 H 10 O 5 ) n + nH 2 O H + nC 6 H 12 O 6 StarchGlucose Hydrolysis of Starch
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