Why Study Chemistry in Biology?

1. Why Study Chemistry in Biology?

2. I. The Atom A. Definition: smallest particle of an element

3. B. Composition

4. Location of Electrons Valence electrons: outermost electrons, participate in BONDING

5. II. Elements A. Definition: substance that cannot be broken down into other substances B. Biologically important elements i. Major: C H O N P S ii. Minor: Ca Fe Mg I Se P K Na Cl

8. III. Chemical Compounds A. Compound definition: a substance containing two or more elements in a fixed ratio • Ex: H2O, NaCl

9. B. Bonds: • Atoms want to fill their outer energy levels to be • To do this, they will meet up with other atoms and either or electrons complete exchange share

10. C o v a l e n t B o n d : 
s h a ri n g I s c a r I n g • Atoms share electrons so that both atoms fill their outer energy level

11. Examples of covalent molecules

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

13. iii. Molecules definition: two or more atoms held together by COVALENT bonds

14. V. WATER LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

16. Questions to think about • Why do put salt on the roads? • Why do we add salt to a pot of pasta water? • At a higher altitude why must we cook “boil” something longer?

17. Human Composition: Cells are 70–90% water

18. B. Plant Composition As much as 95% plants can be made of water

19. C. Formula: H2O

20. D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond.

21. Hydrogen Bonds • Hydrogen Bonds- weak bondsslightly positive H is attracted to the slightly negative O of another water molecule

22. E. Polarity • Polar molecule: molecule in which opposite ends have opposite electric charges • Why? Water is a polar molecule: because Oxygen holds electrons closer

23. The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties. • Cohesion • Adhesion • Solubility • Temperature moderation • The lower density of ice

24. 1-inchpaperclip over-filled water 3oz Dixie cup i. Cohesion 1. Definition: Water “sticks” to each other Ex.: Surface tension

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26. ii. Adhesion 1. Definition: Water molecules are also attracted to certain other molecules. 2. Ex. In trees/plants water goes against gravity Called capillary action

28. iii. Temperature and Water Boiling Point: 100 oC / 212 oF • When you heat molecules move faster • When you cool molecules move slower • Water takes more energy to heat because energy must break hydrogen bonds

29. Does water boil faster if you add salt to it? • Water Boils when it has enough energy for the molecules to leave

30. Freezing Point 0 oC or 32 oF • What would happen if our oceans did not have salt in them? • Why do we put salt on our roads? • Why at effect does salt have on FREEZING POINT?

31. LOW DENSITY OF ICE • Density- amount of matter in a volume • In most substances the solid state is more dense than the liquid state • Water is the opposite ICE IS LESS DENSE THAN WATER and will FLOAT

32. LOW DENSITY OF ICE • WHY? • Hydrogen bonds in ice (solid) keep molecules spaced out

33. LOW DENSITY OF ICE • Floats • Ice insulates the liquid water below allowing life to persist