1. CHAPTER 2 THE CHEMISTRY OF CELLS

2. SO WHAT DOES CHEMISTRY HAVE TO DO WITH BIOLOGY???? Thomas Eisner pioneered chemical ecology –the study of the chemical language of nature He studies how insects communicate via chemical messages

3. BETTER LIVING THROUGH CHEMISTRY…….. Rattlebox moths release a chemical that spiders don’t like This spider caught a rattlebox moth and then let it go

4. ATOMS AND MOLECULES 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.

5. Molecules and ecosystems are at opposite ends of the biological hierarchy –Each level of organization in the biological hierarchy builds on the one below it –At each level, new properties emerge…in other words-the higher up the ladder..the more complicated

6. A biological hierarchy D. Organ: Flight muscle of a moth C. Cell and tissue: Muscle cell within muscle tissue Myofibril (organelle B. Organelle: Myofibril (found only in muscle cells) Myosin A. Molecule: ActinAtom Organ Tissue Cell Organelle Molecule Atom Actin

7. LIFE REQUIRES ABOUT 25 CHEMICAL ELEMENTS A chemical element is a substance that cannot be broken down to other substances by ordinary chemical means About 25 different chemical elements are essential to life

8. Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life

9. IODINE IS A REQUIREMENT Goiters are caused by iodine deficiency

10. ELEMENTS CAN COMBINE TO FORM COMPOUNDS Chemical elements combine in fixed ratios to form compounds Example: sodium + chlorine  sodium chloride

11. Atoms consist of protons, neutrons, and electrons The smallest particle of an element is an atom Different elements have different types of atoms

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

13. Each atom is held together by attractions between the positively charged protons and negatively charged electrons Neutrons are electrically neutral Protons Neutrons Electrons B. Carbon atom Nucleus 6 6 6

14. 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 isotopes –Some isotopes are radioactive

15. 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

16. Electron arrangement determines the chemical properties of an atom Electrons are arranged in shells –The outermost shell determines the chemical properties of an atom –In most atoms, a full outer shell holds eight electrons

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

18. 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 Sodium atom Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl)

19. Sodium and chloride ions bond to form sodium chloride, common table salt Na + Cl –

20. Covalent bonds, the sharing 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

21. Molecules can be represented in many ways