1. CHAPTER 2 The Chemistry of Living Things

2. All Matter Consists of Elements Made of Atoms
Atoms, the smallest functional unit, consist of:
Protons: positive charge, have mass
Neutrons: no charge, have mass
Electrons: negative charge, have no discernable mass
Slide 2.1

4. Isotopes Radioisotopes
Same element, same atomic number = same number of protons and electrons
Different number of neutrons = different weight
Radioisotopes
Are unstable (varies with isotope) ex.: I131 used in the treatment of Grave’s Disease
Emit energy (radiation)
Emit particles
Slide 2.2

5. Atoms Combine to Form Molecules
Joining atoms requires energy
Energy is the capacity to do work
Stored energy = potential energy
Energy in motion, doing work = kinetic energy
Electrons have potential energy
Shells = the energy levels of electrons
Orbitals describe the probable location of an electron .
Slide 2.3

6. Three Types of Chemical Bonds
Table 2.1
Slide 2.4

8. Ionic Bonds
Written NaCl NOT Na-Cl

9. Elements of Living Organisms
Table 2.2
Slide 2.5

10. Life Depends on Water
Water molecules are polar (they have slight electrical charges)
Water is liquid at body temperature
Water can absorb and hold heat energy
Slide 2.6

11. Two Important Biological Functions of Water
Water is the biological solvent
Water helps regulate body temperature
Has high heat of evaporation
Slide 2.7

12. Hydrogen bonds (dotted lines)
Oxygen slightly –ve charge
Hydrogen slightly +ve

13. Water Keeps Ions in Solution
Figure 2.8
Slide 2.8

14. The Importance of Hydrogen Ions
Acids are proton (hydrogen ion) donors, bases accept hydrogen ions
pH Scale = a logarithmic scale of the hydrogen ion concentration (going from a pH of 2 to 4 is a change of 2 numbers= 102, so pH 4 is 100 times less acidic than pH 2
Buffers: minimize pH change
Carbonic acid and bicarbonate act as one of body’s most important buffer pairs
Slide 2.9

15. The pH Scale
Figure 2.10
Slide 2.10

16. The Organic Molecules of Living Organisms
Carbon, the building block of living things:
Comprises 18% of body by weight
Forms four covalent bonds
Can form single or double bonds
Can build micro- or macromolecules
Slide 2.11