Macromolecules (Chap-3 Part A) PDF

Chemical Basis of Life: Macromolecules Key Concepts: The Carbon Atom Formation of Organic Molecules and Macromolecules Carbohydrates Lipids Proteins Nucleic Acids 2  The Carbon Atom Organic molecules contain carbon Organic molecule...

Chemical Basis of Life: Macromolecules Key Concepts: The Carbon Atom Formation of Organic Molecules and Macromolecules Carbohydrates Lipids Proteins Nucleic Acids 2  The Carbon Atom Organic molecules contain carbon Organic molecules are abundant in living organisms Macromolecules are large, complex organic molecules 3  Carbon Carbon has 4 electrons in its outer shell It can make up to four covalent bonds (Octet rule) Usually single or double bonds Carbon can form nonpolar or polar bonds Molecules with polar bonds are water soluble Molecules with nonpolar bonds (like hydrocarbons) are not very water soluble 4  Oxygen is C—C and C—H more electronegative bonds are than carbon; electrically thus, C—O and neutral and C=O bonds are nonpolar.  Propionic polar. acid 5  Functional Groups Groups of atoms with special chemical features that are functionally important Each type of functional group exhibits the same properties in all molecules in which it occurs 6  Isomers Two molecules with an identical molecular formula but different structures and characteristics Structural isomers - contain the same atoms but in different bonding relationships Stereoisomers - identical bonding relationships, but the spatial positioning of the atoms differs in the two isomers Cis-trans isomers - positioning around double bond Enantiomers - mirror image molecules 7 8  Polymer formation by dehydration reactions A molecule of water is removed each time a new monomer is added, thus a “dehydration” reaction The process repeats to form long polymers A polymer can consist of thousands of monomers Dehydration is catalyzed by enzymes 9  Breakdown of a polymer by hydrolysis reactions A molecule of water is added back each time a monomer is released The process repeats to break down long polymer Hydrolysis is catalyzed by enzymes 10  Carbohydrates Composed of carbon, hydrogen, and oxygen atoms Cn(H2O)n Most of the carbon atoms in a carbohydrate are linked to a hydrogen atom and a hydroxyl group 11  Monosaccharides Simplest sugars Most common are 5 or 6 carbons Pentoses Ribose C5H10O5 Deoxyribose (C5H10O4) Hexose Glucose (C6H12O6) 12  Glucose isomers Structural isomers Different arrangement of same elements Example: Glucose and galactose Stereoisomers 𝛃 ‐ 𝐠𝐥𝐮𝐜𝐨𝐬𝐞 Hydroxyl group of carbon 1 is above or below ring D- and L-glucose Enantiomers with mirror image structure 13  Disaccharides Composed of two monosaccharides Joined by dehydration or condensation reaction Glycosidic bond Broken apart by hydrolysis Examples: sucrose, maltose, lactose 14 15  Polysaccharides Many monosaccharides linked together to form long polymers Examples: Energy storage – starch, glycogen Structural – cellulose, chitin 16  Lipids Composed predominantly of hydrogen and carbon atoms Defining feature of lipids is that they are nonpolar and therefore very insoluble in water Include fats, phospholipids, steroids, waxes Lipids comprise about 40% of the organic matter in the average human body 17  Fats Also known as triglycerides or triacylglycerols Formed by bonding glycerol to 3 fatty acids Joined by dehydration; broken apart by hydrolysis The hydrogens from The new bond created is The hydroxyl groups from each hydroxyl group called an ester bond. in glycerol are each carboxyl group of the removed. 3 fatty acids are removed. 18  Fatty acids Saturated – all carbons linked by single bonds Tend to be solid at room temperature Unsaturated – contain one or more double bonds Tend to be liquid at room temperature (known as oils) Cis forms naturally; trans formed artificially Trans fats are linked to disease 19  Animal fats are usually saturated fats Plant fats are usually unsaturated fats High temperature converts After cooling, saturated fats solid, saturated fasts to liquid. Unsaturated fats have low return to their solid form. melting points and are liquid at room temperature. 20  Fats Fats are important for energy storage 1 gram of fat stores more energy than 1 gram of glycogen or starch Fats can also be structural, providing cushioning and insulation 21  Phospholipids Formed from glycerol, two fatty acids and a phosphate group Phospholipids are amphipathic molecules Phosphate head – polar / hydrophilic Fatty acid tail – nonpolar / hydrophobic 22 23  Steroids Four interconnected rings of carbon atoms Usually insoluble in water Example: Cholesterol Tiny differences in structure can lead to profoundly different, specific biological properties Estrogen versus testosterone 24 25