CHAPTER 2 The Chemical Basis of Life

1. CHAPTER 2The Chemical Basis of Life

2. Thomas Eisner and the Chemical Language of Nature • Thomas Eisner pioneered _______ __________ • the study of the chemical language of nature • He studies how insects communicate via chemical messages

3. Water in three different states: 5 States of matter

4. ATOMS AND MOLECULES The emergence of biological function starts at the chemical level • Everything an organism is and does depends on chemistry • Chemistry is in turn dependent on the arrangement of atoms in molecules • In order to understand the whole, biologists study the parts (reductionism)

5. D. Organ: Flight muscle of a moth • A ________ _________ Rattlebox moth C. Cell and tissue: Muscle cell within muscle tissue Myofibril (organelle) B. Organelle: Myofibril (found only in muscle cells) Actin Myosin Atom A. Molecule: Actin

6. A chemical _____ is a substance that cannot be broken down to other substances by ordinary chemical means • About ____ different chemical elements are essential to _____ lead

7. Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life • _________ Table 2.2

8. Goiters are caused by iodine deficiency Figure 2.2

9. 2.4 Atoms consist of protons, ________, and electrons • The smallest particle of an element is an _____ • Different ______ have different types of atoms

10. The nucleus is surrounded by electrons • An atom is made up of protons and neutrons located in a central nucleus 2 Protons Nucleus 2 Neutrons 2 Electrons A. Helium atom

11. Each atom is held together by attractions between the positively charged protons and ________charged electrons • Neutrons are electrically _______ 6 Protons Nucleus 6 Neutrons 6 Electrons B. Carbon atom

12. Atoms of each element are distinguished by a specific number of protons • The number of neutrons may vary • Variant forms of an element are called ________ • Some isotopes are ________

13. 2.5 Connection: Radioactive isotopes can help or harm us • Radioactive isotopes can be useful tracers for studying biological processes • PET scanners use radioactive isotopes to create anatomical images Figure 2.5A Figure 2.5B

14. 2.3 Elements can combine to form compounds • Chemical elements combine in fixed ratios to form _________ • Example: sodium + chlorine  sodium chloride Reactants Products

15. 2.6 Electron arrangement determines the chemical properties of an atom • Electrons are arranged in _______ • The outermost shell determines the chemical properties of an atom • In most atoms, a full outer shell holds _____ electrons

16. Atoms whose shells are not full tend to interact with other atoms and ___, ____, or ______ electrons Outermost electron shell (can hold 8 electrons) Electron First electron shell (can hold 2 electrons) HYDROGEN (H) Atomic number = 1 CARBON (C) Atomic number = 6 NITROGEN (N) Atomic number = 7 OXYGEN (O) Atomic number = 8 Figure 2.6

17. 2.7 Ionic bonds are attractions between ions of opposite charge • When atoms gain or lose electrons, charged atoms called ions are created • An electrical attraction between ions with opposite charges results in an ionic bond – + Na Cl Na Cl Na Sodium atom Cl Chlorine atom Na+ Sodium ion Cl– Chloride ion Figure 2.7A Sodium chloride (NaCl)

18. 2.8 Covalent bonds, the _____ of electrons, join atoms into molecules • Some atoms share outer shell electrons with other atoms, forming covalent bonds • Atoms joined together by covalent bonds form molecules

19. REARRANGEMENTS OF ATOMS Chemical reactions rearrange matter • In a chemical reaction: • reactants interact • atoms rearrange • products result 2 H2 + O2  2 H2O

20. 2.15 The chemistry of life is sensitive to acidic and basic conditions • A compound that releases H+ ions in solution is an acid, and one that accepts H+ ions in solution is a base • Acidity is measured on the pH scale: • 0-6 is acidic • 8-13 is basic OH- Hydroxide Ion Alkaline • Pure water and solutions that are neither basic nor acidic are neutral, with a pH of 7

21. pH scale H+ OH– Lemon juice; gastric juice • The pH scale Increasingly ACIDIC (Higher concentration of H+) Grapefruit juice Acidic solution Tomato juice Urine NEUTRAL [H+] = [OH–] PURE WATER Human blood Seawater Neutral solution Increasingly BASIC (Lower concentration of H+) Milk of magnesia Household ammonia Household bleach Oven cleaner Basic solution

22. Cells are kept close to pH 7 by buffers • Buffers are substances that resist pH change • They accept H+ ions when they are in excess and donate H+ ions when they are depleted • Buffers are not foolproof