1. 1 11/9/2015 ATOMS

2. 2 11/9/2015 Major atoms in biology n C H O N S P n # of atoms in outer shell – H, 1 – C4 – N, P5 – O, S 6

3. 3 11/9/2015 C N P S Atoms are sociable H O H Chemical bonds

4. 4 11/9/2015 Chemical bonds..... Covalent Noncovalent Strong Puny but important

5. 5 11/9/2015 Atoms attached via shared electrons in outer shells H O H H HO Covalent bonds C C C CC C

6. 6 11/9/2015 e.g. CH3 - CH3, ethane Covalent bonds stable (strong)

7. 7 11/9/2015 Covalent bond cleavage CH3:CH3--> CH3 + CH3 Reactant Products (Methyl radicals) (Ethane CH3-CH3)

8. 8 11/9/2015 Covalent bond cleavage CH3:CH3--> CH3 + CH3 Reactant Products  E = +83 kcal/mol  E is the difference between the energy of reactants and products

9. 9 11/9/2015 Covalent bond strengths High bond strength confers stability 0-H 110 C-H 99 C-C 83 C=CC=C 146

10. 10 11/9/2015 Double bonds restrict rotation H H H H Molecule is planar (flat) e.g. Ethylene (CH 2 =CH 2 )

11. 11 11/9/2015 Covalent bonds are orientated in space H H O 104.5 deg

12. 12 11/9/2015 CovalentNon-covalent 1-5 4 kinds..... Bond strength (kcal/mol) 50-195

13. 13 11/9/2015 Non-covalent bonds Hydrogen bonds ionic bonds van der Waal's interactions hydrophobic interactions

14. 14 11/9/2015 Non-covalent bonds Hydrogen bonds e.g. in liquid water oxygen,  hydrogen, 

15. 15 11/9/2015 Hydrogen bond In liquid water Each molecule may be H-bonded to 4 others. Bonds are transient

16. 16 11/9/2015 Typical Hydrogen bonds H O or H N

17. 17 11/9/2015 Ionic bonds Non-covalent bonds (cont.) Result of attraction between + and - charges of ionized atoms e.g. Na + Cl -

18. 18 11/9/2015 Ionic bonds NaCl dissolved in H 2 O Na + Cl Note the tight shells of water molecules Hydrated diameter of ions is important in permeability

19. 19 11/9/2015 Van der Waals interactions Non-covalent interactions (cont.) Due to electron fluxes any atom can become a  transient dipole

20. 20 11/9/2015 Van der Waals interactions Non-covalent interactions (cont.)   2 atoms in van der Waals contact  

21. 21 11/9/2015 Van der Waals interactions Atoms are very close But not close enough so that their electron shells overlap. If so, they repel each other You’re disgusting!

22. 22 11/9/2015 Our next Attraction Hydrophobia Starring a cast of thousands of greasy characters Hydrocarbons

23. 23 11/9/2015 Non-covalent interactions (cont) Hydrophobic interactions C H H C H H C H H C H H C H H H Hydrocarbons C H H C H H C H H H Combined hydrophobic and van der Waals interactions

24. 24 11/9/2015 O NH 3 O CH 3 2 NH 2 CH 2 O H C 2 C O 2 2 2 3 3 3 2 Bonds at work, H-bonds, ionic and vd Waals+ hydrophobic bonds Protein

25. 25 11/9/2015 How many water molecules in a teaspoonful? As many as the teaspoonfuls of water present in the Atlantic Ocean Trivia Time A one, a two, a three...

26. 26 11/9/2015 An everyday protein molecule, hemoglobin All your hemoglobin alpha chains are identical with 574 amino acids chained together in precise sequence In the past second you have just assembled 400 million million of them

27. 27 11/9/2015