1. Lecture 2 NatSci II Josephine B. Guerrero, MD Asst. Professor, Department of Biology

2. Concepts:  Matter – anything that has mass and occupies space  Atomic theory – all elements are composed of atoms; each element with a unique number of electrons, protons and neutrons  Elements – simplest form that cannot be broken down further  Compounds – composed of two or more elements joined by a chemical bond

3. Chemical Bonds 1. Covalent bonds 2. Hydrogen bonds 3. Ionic bonds 4. Electrostatic bonds

4. Elements found in living systems

5. What is the difference between organic and inorganic molecules? Inorganic Molecules – made up of elements except C Organic Molecules – made up of C except CO and CO 2

6. Acids, Bases and Buffers  Acids – release H + ; proton donors  Bases – release OH - ; proton acceptors  Salt – product of neutralization process between an acid and a base  Buffers – substances that help resist changes in pH; mixture of a weak acid and its conjugate base or a weak base and its conjugate acid

7. [H + ] pH Example Acids 1 X 10 0 0HCl 1 x 10 -1 1Stomach acid 1 x 10 -2 2Lemon juice 1 x 10 -3 3Vinegar 1 x 10 -4 4Soda 1 x 10 -5 5Rainwater 1 x 10 -6 6Milk Neutral 1 x 10 -7 7Pure water Bases 1 x 10 -8 8Egg whites 1 x 10 -9 9Baking soda 1 x 10 -10 10Tums ® antacid 1 x 10 -11 11Ammonia 1 x 10 -12 12 Mineral lime - Ca(OH) 2 1 x 10 -13 13Drano ® 1 x 10 -14 14NaOH

8. CO 2 +H2OH2O[H 2 CO 3 ]H+H+ +HCO 3 - produced by metabolism always available in equilibrium with species on either side produced by metabolism pre-existing blood buffer directly expelled in lung adjusted in kidney via physiologic mechanism s unrelated to pH converted to products on left by carbonic anhydrase (RBC) adjusted in kidney or reacts with bicarbonate to make products on left adjusted in kidney or reacts with H+ to make products on left

9. Biomolecules:  Carbohydrate  Lipids  Proteins  Nucleotides

10. Carbohydrates  Simple sugars or monosaccharides forming long chains of polysaccharides  Ranges from a 4C, 5C or 6C monosaccharide  Useful as an energy source: glucose

12. Lipids  Also known as fatty acids; composed of a glycerol molecule with three fatty acid chains  Saturated vs. unsaturated fatty acid  Useful as a energy storage material and heat insulation

13. Proteins  Composed of amino acids connected together by peptide bond  Either a structural molecule or one with enzymatic functions  1 o, 2 o, 3 o, 4 o forms

15. Primary Form

16. Secondary Form

17. Tertiary Form

19. Nucleic Acids  Building blocks: nucleotides  Form the genetic material of living systems  DNA or RNA  In eukaryotic systems, dsDNA are coiled around histone proteins which become visible during cell division as chromosomes

20. Nucleotide molecule

22. Central Dogma of Genetics