Why Study Chemistry in Biology?

1. Why Study Chemistry in Biology?

4. I. Atoms Definition: smallest particle of an element

6. B. Composition C. If Neutral Atom: # protons = # electrons

7. II. Elements • Definition: substance that cannot be broken down into other substances B. Biologically important elements i. Major: C H O N ii. Minor: Ca Fe Mg I Se P K Na Cl • Symbol: usually from first letter or two of full name

9. Elements Con’t. Mass Number Atomic Mass 12.0107 amu Atomic Number: # of protons in nucleus

10. E. Atomic Mass / Mass Number Atomic mass: count of the total number of protons and neutrons in an atom's nucleus

11. F. Isotopes i. Definition: forms of the same element have same # of protons but different # of neutrons Mass Number ii. Radioactive isotopes: An isotope having an unstable nucleus that decomposes spontaneously

12. G. Chemical Compounds i. Molecules definition: two or more atoms held together by COVALENT bonds

13. Compound definition: a substance containing two or more elements in a fixed ratio • Ex: H2O, NaCl

14. Decoding Chemical Formulas?? C6H12O6 Element subscript is the NUMBER of ATOMS So in this molecule, there are 6 carbon atoms, 12 hydrogen, and 6 oxygen

15. 2H2O • The number in front of H2O means two entire molecules of H2O • Think of it like 2 x (H20) • Sooooo… how many total atoms of H are there? • Of oxygen?

16. III. Bonding • Atoms want to fill their outer energy levels to be • In order to do this, they will meet up with other atoms and either share or exchange electrons happy

17. A. Covalent Bonds • Atoms share electrons so that both atoms fill their outer energy level

18. B. Ionic Bonds: gimme that electron! • Atoms transfer electrons, becoming (+) or (-) charged • This attraction brings them together • Ex: Na and Cl

19. Ions > An electrically charged atom

20. Carbon Has 4 electrons in outer level, needs 4 more to fill its orbital Hydrogen Has 1 electron, needs 1 to fill its orbital Can form ONE bond Can form FOUR bonds

22. IV. Water • Human Composition: 65–90% water • Plant Composition: 80-90% • Formula: H2O • Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond. ii. Covalent bonds: are shared between oxygen and hydrogen in a single molecule.

23. V. Water (con.’t) • Water is a polar molecule: i. Definition of polarity: molecule that has opposite electrical charges on opposite ends ii. Why? Oxygen does not share electrons equally- pulls them closer to itself, making it more negative and Hydrogen more positive

24. V. Water (con.’t) F. Unique molecule: i. Cohesion: 1. Definition: molecules of same kind stick to one another 2. Example: Surface tension; trees transporting water from roots to leaves

25. Adhesion: 1. Definition: attraction that occurs between unlike molecules 2. Example: Water molecules and cotton string.

26. Solutions: 1. Water is able to dissolve other polar and ionic compounds when mixed by causing the ions to break away and surround them. Ex.: Salt Water

27. Suspensions a. Definition: A heterogeneous mixture in which particles settle out of solvent-like phase some time after their introduction b. Example: oil & water iv. Boiling Point: water will boil at 100C or 212F

28. Acids and Bases i. A water molecule can react to form ions ii. An ion is when a molecule breaks down and the atoms get a charge 1. Example: H+ and OH-

29. iii. pH Scale 1. How? Scale of 0-14; each pH unit represents a tenfold change in the concentration of H+ ions 2. Acid definition: pH 0-6 3. Base definition: pH 8-14

30. 4. Buffer definition: substances that cause a solution to resist changes in pH.; works by accepting H+ ions when levels rise and donating H+ ions when levels fall, maintaining a constant pH a. Weak acid or base