Chapter 2 Chemical Principles PDF Summary

Chapter Summary 2 Introduction The interactions of microorganisms among themselves and with their environment are determined by their metabolic abilities (e.g., quorum sensing, oxygen consumption, nitrogen transformations). Microorganisms provide essential models that give us fundamental knowledge a...

Chapter Summary 2 Introduction The interactions of microorganisms among themselves and with their environment are determined by their metabolic abilities (e.g., quorum sensing, oxygen consumption, nitrogen transformations). Microorganisms provide essential models that give us fundamental knowledge about life processes. 1. The science of the interaction between atoms and molecules is called chemistry. 2. The metabolic activities of microorganisms involve complex chemical reactions. 3. Microbes break down nutrients to obtain energy and to make new cells. The Structure of Atoms 1. An atom is the smallest unit of a chemical element that exhibits the properties of that element. 2. Atoms consist of a nucleus, which contains protons and neutrons, and electrons, which move around the nucleus. 3. The atomic number is the number of protons in the nucleus; the total number of protons and neutrons is the atomic mass. Chemical Elements 4. Atoms with the same number of protons and the same chemical behavior are classified as the same chemical element. 5. Chemical elements are designated by abbreviations called chemical symbols. 6. About 26 elements are commonly found in living cells. 7. Atoms that have the same atomic number (are of the same element) but different atomic masses are called isotopes. Electronic Configurations 8. In an atom, electrons are arranged around the nucleus in electron shells. 9. Each shell can hold a characteristic maximum number of electrons. 10. The chemical properties of an atom are due largely to the number of electrons in its outermost shell. Organic Compounds 1. Organic compounds always contain carbon and hydrogen. 2. Carbon atoms form up to four bonds with other atoms. 3. Organic compounds are mostly or entirely covalently bonded. Structure and Chemistry 4. A chain of carbon atoms forms a carbon skeleton. 5. Functional groups of atoms are responsible for most of the properties of organic molecules. 6. The letter R may be used to denote the remainder of an organic molecule. 7. Frequently encountered classes of molecules are R—OH (alcohols) and R—COOH (organic acids). 8. Small organic molecules may combine into very large molecules called macromolecules. 9. Monomers usually bond together by dehydration synthesis, or condensation reactions, that form water and a polymer. 10. Organic molecules may be broken down by hydrolysis, a reaction involving the splitting of water molecules. Carbohydrates 11. Carbohydrates are compounds consisting of atoms of carbon, hydrogen, and oxygen, with hydrogen and oxygen in a 2:1 ratio. 12. Monosaccharides contain from three to seven carbon atoms. 13. Isomers are two molecules with the same chemical formula but different structures and properties—for example, glucose (C6H12O6) and fructose (C6H12O6). 14. Monosaccharides may form disaccharides and polysaccharides by dehydration synthesis. Lipids 15. Lipids are a diverse group of compounds distinguished by their insolubility in water. 16 Simple lipids (fats) consist of a molecule of glycerol and three molecules of fatty acids. 17. A saturated lipid has no double bonds between carbon atoms in the fatty acids; an unsatu- rated lipid has one or more double bonds. Saturated lipids have higher melting points than unsaturated lipids. 18. Phospholipids are complex lipids consisting of glycerol, two fatty acids, and a phosphate group. 19. Steroids have carbon ring structures; sterols have a functional hydroxyl group. Proteins 20. Amino acids are the building blocks of proteins. 21. Amino acids consist of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. 22. Twenty amino acids occur naturally in proteins. 23. By linking amino acids, peptide bonds (formed by dehydration synthesis) allow the formation of polypeptide chains. 24. Proteins have four levels of structure: primary (sequence of amino acids), secondary (helices or pleated), tertiary (overall three-dimensional structure of a polypeptide), and quaternary (two or more polypeptide chains). 25. Conjugated proteins consist of amino acids combined with inorganic or other organic compounds. Nucleic Acids 26. Nucleic acids—DNA and RNA—are macromolecules consisting of repeating nucleotides. 27. A nucleotide is composed of a pentose, a phosphate group, and a nitrogen-containing base. A nucleoside is composed of a pentose and a nitrogen-containing base. 28. A DNA nucleotide consists of deoxyribose (a pentose) and one of the following nitrogen- containing bases: thymine or cytosine (pyrimidines) or adenine or guanine (purines). 29. DNA consists of two strands of nucleotides wound in a double helix. The strands are held together by hydrogen bonds between purine and pyrimidine nucleotides: AT and GC. 30. Genes consist of sequences of nucleotides. 31. An RNA nucleotide consists of ribose (a pentose) and one of the following nitrogen- containing bases: cytosine, guanine, adenine, or uracil. Adenosine Triphosphate (ATP) 32. ATP stores chemical energy for various cellular activities. 33. When the bond to ATP’s terminal phosphate group is hydrolyzed, energy is released. 34. The energy from oxidation reactions is used to regenerate ATP from ADP and inorganic phosphate. Copyright © 2019 Pearson Education, Inc. CHAPTER 2 Chemical Principles 13