1. Chapter 2: The Molecules of Cells

2. Two types of molecules:
Organic
Created by living things
Contains rings or long chains of carbon atoms
Other atoms (i.e. hydrogen, oxygen, nitrogen, etc.) are attached
2. Inorganic
Does NOT contain carbon
Need by but not created by living things

3. 2.2 Water and Living Things p. 26-29
Covalently bonded (share electrons)
Polar
One end is slightly positive (H+); other end is slightly negative (O2-)

4. Hydrogen Bonding Weak bond
Slightly positive hydrogen atom is attracted to a slightly negative atom
Occurs in polar covalent bonds

5. Properties of Water Water is a universal solvent.
Blood carries dissolved solutes
Oceans carry dissolved solutes

6. Water molecules are cohesive and adhesive.
like molecules sticking together = cohesion
Example: surface tension
unlike molecules sticking together = adhesion
Example: water’s meniscus
excellent transport system (outside and within living organisms)

7. Water has a high heat capacity.
Requires a large amount of energy to change temperature
Helps regulate body temperature

8. Water has a high heat of vaporization.
Takes a large amount of heat to change water into steam
Cooling effect of sweat evaporation makes use of this

9. Frozen water is less dense than liquid water.
Protects aquatic organisms

10. Lubricant
Swallowing, joints

11. Acids and Bases When water dissociates,
hydrogen ions (H+) = hydroxide ions (OH-)
neutral solution (pH 7)

12. ex) HCl in gastric juices
Acidic Solutions
[H+] > [OH-]
sour
HCl H+ + Cl-
ex) HCl in gastric juices

13. Basic Solutions [H+] < [OH-] Bitter & slippery An example:
NaOH Na+ + OH-

14. The pH Scale
Ranges from
A pH below 7 is acidic [H+] > [OH-]
A pH above 7 is alkaline [OH-] > [H+]
A pH of 7 is neutral [H+] = [OH-]

15. The pH Scale

16. The pH Scale
Each unit change in pH represents a change of 10X

17. Buffers and pH
A buffer is a chemical(s) that keep pH within normal limits.
Bicarbonate ions (HCO3-) and carbonic acid (H2CO3) found in human blood buffers the pH to 7.4

18. If hydrogen ions (H+) are added to the blood, this reaction occurs:
H+ + HCO H2CO3
If hydroxide ions (OH-) are added to the blood, this reaction occurs:
OH- + H2CO3 HCO3- + H2O