1. Chemical Foundations for Cells Chapter 2

2. You are chemical, and so is every living and nonliving thing in the universe. You are chemical, and so is every living and nonliving thing in the universe.

3. Elements Fundamental forms of matter Fundamental forms of matter Can’t be broken apart by normal means Can’t be broken apart by normal means 92 occur naturally on Earth 92 occur naturally on Earth

4. Most Common Elements in Living Organisms OxygenHydrogenCarbonNitrogen

5. What Are Atoms? Smallest particles that retain properties of an element Smallest particles that retain properties of an element Made up of subatomic particles: Made up of subatomic particles: Protons (+) Protons (+) Electrons (-) Electrons (-) Neutrons (no charge) Neutrons (no charge)

6. Atomic Number Number of protons Number of protons All atoms of an element have the same atomic number All atoms of an element have the same atomic number Atomic number of hydrogen = 1 Atomic number of hydrogen = 1 Atomic number of carbon = 6 Atomic number of carbon = 6

7. Mass Number Number of protons + Number of neutrons Isotopes vary in mass number

8. Isotopes Atoms of an element with different numbers of neutrons (different mass numbers) Atoms of an element with different numbers of neutrons (different mass numbers) Carbon 12 has 6 protons, 6 neutrons Carbon 12 has 6 protons, 6 neutrons Carbon 14 has 6 protons, 8 neutrons Carbon 14 has 6 protons, 8 neutrons

9. What Determines whether Atoms Will Interact? The number and arrangement of their electrons

10. Electrons Carry a negative charge Carry a negative charge Repel one another Repel one another Are attracted to protons in the nucleus Are attracted to protons in the nucleus Move in orbitals - volumes of space that surround the nucleus Move in orbitals - volumes of space that surround the nucleus Z X When all p orbitals are full y

11. Shell Model First shell First shell Lowest energy Lowest energy Holds 1 orbital with up to 2 electrons Holds 1 orbital with up to 2 electrons Second shell Second shell 4 orbitals hold up to 8 electrons 4 orbitals hold up to 8 electrons CALCIUM 20p+, 20e -

12. Electron Vacancies Unfilled shells make atoms likely to react Unfilled shells make atoms likely to react Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells CARBON 6p+, 6e - NITROGEN 7p+, 7e - HYDROGEN 1p+, 1e -

13. Chemical Bonds, Molecules, & Compounds Bond is union between electron structures of atoms Bond is union between electron structures of atoms Atoms bond to form molecules Atoms bond to form molecules Molecules may contain atoms of only one element - O 2 Molecules may contain atoms of only one element - O 2 Molecules of compounds contain more than one element - H 2 O Molecules of compounds contain more than one element - H 2 O

14. Chemical Bookkeeping Use symbols for elements when writing formulas Use symbols for elements when writing formulas Formula for glucose is C 6 H 12 O 6 Formula for glucose is C 6 H 12 O 6 6 carbons 6 carbons 12 hydrogens 12 hydrogens 6 oxygens 6 oxygens

15. Chemical Bookkeeping Chemical equation shows reaction Chemical equation shows reaction Reactants ---> Products Equation for photosynthesis: Equation for photosynthesis: 6CO 2 + 6H 2 O ---> + C 6 H 12 O 12 + 6H 2 O 6CO 2 + 6H 2 O ---> + C 6 H 12 O 12 + 6H 2 O

16. Important Bonds in Biological Molecules Ionic Bonds Covalent Bonds Hydrogen Bonds

17. Ionic Bonding Ionic Bonding One atom loses electrons, becomes positively charged ion One atom loses electrons, becomes positively charged ion Another atom gains these electrons, becomes negatively charged ion Another atom gains these electrons, becomes negatively charged ion Charge difference attracts the two ions to each other Charge difference attracts the two ions to each other

18. Formation of NaCl Sodium atom (Na) Sodium atom (Na) Outer shell has one electron Outer shell has one electron Chlorine atom (Cl) Chlorine atom (Cl) Outer shell has seven electrons Outer shell has seven electrons Na transfers electron to Cl, forming Na + and Cl - Na transfers electron to Cl, forming Na + and Cl - Ions remain together as NaCl Ions remain together as NaCl

19. Covalent Bonding Atoms share a pair or pairs of electrons to fill outermost shell Single covalent bond Double covalent bond Triple covalent bond Molecular hydrogen

20. Polar or Nonpolar Bonds Nonpolar if atoms share electrons equally Nonpolar if atoms share electrons equally Hydrogen gas (H - H) Hydrogen gas (H - H) Polar if electrons spend more time near nucleus with most protons Polar if electrons spend more time near nucleus with most protons Water Water Electrons more attracted to O nucleus than to H nuclei Electrons more attracted to O nucleus than to H nuclei

21. Hydrogen Bonding Atom in one polar covalent molecule is attracted to oppositely charged atom in another such molecule or in same molecule Atom in one polar covalent molecule is attracted to oppositely charged atom in another such molecule or in same molecule Water molecule Ammonia molecule Figure 2.11a Page 27

22. Hydrogen Bonding in DNA Figure 2.11d Page 27

23. Water Is a Polar Covalent Molecule Molecule has no net charge Molecule has no net charge Oxygen end has a slight negative charge Oxygen end has a slight negative charge Hydrogen end has a slight positive charge Hydrogen end has a slight positive charge HH O Figure 2.12a Page 28

24. Properties of Water Bonds to hydrophilic substances Bonds to hydrophilic substances Repels hydrophobic ones Repels hydrophobic ones Temperature stabilizing Temperature stabilizing Expands when it freezes Expands when it freezes Cohesive Cohesive Capacity to dissolve substances Capacity to dissolve substances

25. Liquid water Ice Figure 2.12b,c Page 28

26. Hydrogen Ions: H + Unbound protons Unbound protons Have important biological effects Have important biological effects Form when water ionizes Form when water ionizes

27. The pH Scale Measures H + concentration of fluid Measures H + concentration of fluid Change of 1 on scale means 10X change in H + concentration Change of 1 on scale means 10X change in H + concentration Highest H + Lowest H + 0---------------------7-------------------14 Acidic Neutral Basic

28. Examples of pH Pure water is neutral with pH of 7.0 Pure water is neutral with pH of 7.0 Acidic Acidic Stomach acid: pH 1.0 - 3.0 Stomach acid: pH 1.0 - 3.0 Lemon juice: pH 2.3 Lemon juice: pH 2.3 Basic Basic Seawater: pH 7.8 - 8.3 Seawater: pH 7.8 - 8.3 Baking soda: pH 9.0 Baking soda: pH 9.0

29. Acids & Bases Acids Acids Donate H + when dissolved in water Donate H + when dissolved in water Acidic solutions have pH < 7 Acidic solutions have pH < 7 Bases Bases Accept H + when dissolved in water Accept H + when dissolved in water Acidic solutions have pH > 7 Acidic solutions have pH > 7

30. Salts Compounds that release ions other than H + and OH - when dissolved in water Compounds that release ions other than H + and OH - when dissolved in water Example: NaCl releases Na + and Cl – Example: NaCl releases Na + and Cl – Many salts dissolve into ions that play important biological roles Many salts dissolve into ions that play important biological roles