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Across 2. a chemical bond that involves sharing a pair of electrons between atoms in a molecule 5. the basic unit of a chemical element 6. any organic molecule that is produced by a living organism 7. a substance that accelerates a chemical reaction without itself being affected 9. any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents 11. a compound that does not contain carbon 12. a weak bond involving the sharing of an electron with a hydrogen atom 15. a substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction 16. a group of atoms bonded together 17. a process in which one or more substances are changed into others 18. a molecule that can be bonded to other identical molecules to form a polymer 19. a carboxylic acid consisting of a hydrocarbon chain and a terminal carboxyl group 20. any of a class of nitrogenous organic compounds that consist of large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms

Down 1. a simple organic compound containing both a carboxyl and an amino group 2. any of a large group of organic compounds occurring in foods and living tissues 3. a complex organic substance present in living cells 4. a chemical reaction that involves the loss of water from the reacting molecule 8. a carbon-containing molecule 10. a large molecule composed of repeating structural units typically connected by covalent chemical bonds 12. the chemical breakdown of a compound due to reaction with water 13. the substances that make up the chromosomes and the genes 14. a white crystalline carbohydrate used as a sweetener and preservative