BE101 Introduction to Life Sciences Lecture 3 Carbohydrates Background reading: Concepts of Biology pg 39-42 Biological macromolecules Wet weight of cell: Water Dry weight of cell? Carbohydrates (sugars) All form polymers except lipids Lipids (fats) Nucleic acids (DNA, RNA) Proteins 1 https://www.khanacademy.org/science/biology/macromolecules Carbohydrates ( Saccharides,sugars) ➢ Simple sugars (monosaccharides) building blocks of carbohydrates; 3-7 carbon atoms ➢ Complex carbohydrates: disaccharides (common sugar), oligosaccharides (2-10 monomers), polysaccharides (many repeating units, storage form) ➢ formed from carbon, hydrogen, oxygen; chemical formula (CH2O)n, where n represents number of carbon atoms Principles of Biology Monosaccharides have variety of structures & classifications. Classified by: location of carbonyl group (orange), length of carbon skeleton (no. carbon atoms in middle of each structure), spatial arrangement of hydroxyl groups around asymmetric carbons of structure (purple) Principles of Biology Monosaccharides have a variety of structures and classifications. Principles of Biology Monosaccharides have a variety of structures and classifications. Isomeric monosaccharides: same chemical formula but slightly different structures - Glucose & galactose stereoisomers of each other - Fructose structural isomer of glucose and galactose Principles of Biology Sugars can transform between linear and ring structures Linear form of glucose rarely exists in nature –OH group angled toward carbon-carbon bond Beta form is more stable Principles of Biology –OH group angled toward the carbon-oxygen bond Fructose Linear & ring form of carbohydrate fructose, with its intermediate form in between Monosaccharides: relatively bulky, inefficient to store, organisms convert those not immediately needed into polysaccharides Principles of Biology Disaccharides = 2 linked monosaccharides Dehydration reaction:–OH group of one monosaccharide combines with hydrogen atom of another monosaccharide, releasing H2O and forming covalent bond (glycosidic linkage) Glucose Glucose Glucose Fructose Maltose & sucrose (table sugar) are disaccharide sugars made up of two monomers Lactose: glucose and galactose (found naturally in milk) Principles of Biology Polysaccharides: storage Distinguishing features of important polysaccharides. Principles of Biology Microscopy images of storage polysaccharides, glycogen and starch. a) b) Mouse liver cells reveal accumulated glycogen granules, magenta staining (400x magnification). Transmission electron microscopy of chloroplast with starch granules ("st") (Scale bar: 500 nm). Principles of Biology ➢ Glucose: food, photosynthesis (plants) ➢ Energy source/fuel ➢ Extra sugar stored as glycogen(liver, muscles), starch (plants) https://opentextbc.ca/anatomyandphysiology/chapter/24-1-overview-of-metabolic-reactions/ http://encyclopedia.lubopitko-bg.com/Pancreas.html