1. Fundamentals of Biochemistry
Third Edition
Donald Voet • Judith G. Voet • Charlotte W. Pratt
Chapter 2
Water
Copyright © 2008 by John Wiley & Sons, Inc.

2. Why is Water Important?
Most biological molecule’s shapes are influenced by physical & chemical properties of water
Most biochemical reactions take place in water
Water, or components of water participate in many biological reactions

3. Section 1 – Physical Properties of Water

4. Hydrogen bonding is very important in explaining the properties of water.
Each water molecule can make up to 4 hydrogen bonds

5. Solid water
Liquid water

6. Table 2-1

8. Why do nonpolar substance not like water?

11. Emulsions and Surfactants
Emulsion: One liquid suspended in fine droplets in another liquid which to not mix.
Ex: oil and water
Salad dressing
Mayonnaise
Emulsifier: a chemical liaison between two incompatible liquids to make them stable, typically a surfactant
Surfactant: agents that lower the surface tension of a liquid – amphiphilic – love’s both, contains both a polar and non-polar group

12. Surfactants Detergents Foaming agents Fabric softener Defoaming agents
Emulsifiers
Paints
Adhesives
Inks
Anti-fogging
Soil remediation
Wetting
Ski wax, snowboard wax
Deinking (particularly during the enzymatic deinking of used paper during the recycling and repulping process)
Foaming agents
Defoaming agents
Laxatives
Agrochemical formulations
Herbicides
Insecticides
Quantum dot coating
Biocides (sanitizers)
Hair conditioners (after shampoo)
Spermicide (nonoxynol-9)

13. Types of surfactants
Non-ionic – Used in drug delivery, cosmetics, and shampoos
Ex: Fatty alcohols – drug delivery
cocamide MEA – foaming agent in shampoo
Anionic – Negatively charged head group, used in drug delivery, soaps, shampoos
Ex: SDS – sodium dodecyl sulfate – protein separation, car soap, toothpaste, some aspirins
Cationic – positively charged head group, aniseptics, herbicides
Ex: Cetylpyridinium chloride (CPC) – antiseptic, mouthwash, anti-sore throat spray

14. Lipids, Water, and Disease
Medical surfactant – surface active lipoprotein
Coats outside of aveoli
Important to inspiration
Creates equal surface tension on all aveoli
Aides in gas exchange
Acts as a pollution filter

15. Osmosis – The movement of WATER across a semipermeable membrane
Diffusion – the movement of other stuff across a concentration gradient

16. Osmotic Pressure
Osmotic Pressure = ∏ = the force required to resist water movement
van‘t Hoff equation: ∏ = icRT
ic = osmolarity of the solution
i = number of solutes per molecule
(NaCl = 2)
c = concentration in molarity
R = gas constant J/mol
T = temperature in Kelvin

17. Osmolarity in Biology
Hypertonic: solution has a higher osmolarity than the cytosol
Hypotonic: solution has a lower osmolarity than the cytosol

18. Practice Which of the following solutions has an osmolarity of 3?
3M Na3PO4
0.43M Na3PO4
0.75 M Na3PO4
3 M NaCl
1.5 M NaCl

19. Practice
You want to isolate a lysosome to study it in the lab. Assuming that the only components inside a lysosome are KCl (0.1M) and NaCl (0.03M), how much sucrose (342 g/mol) do you need to make 1 liter of an isotonic solution to isolate the lysosomes?

20. Practice
You want to isolate a lysosome to study it in the lab. Assuming that the only components inside a lysosome are KCl (0.1M) and NaCl (0.03M), how much glycogen (18,000 g/mol) do you need to make 1 liter of an isotonic solution to isolate the lysosomes?

22. Figure 2-14

23. Section 2 – Chemical Properties of Water

24. 1 2 3

25. General acid reaction
Abbreviated acid reaction
Abbreviated acid reaction

26. 4 5 6
Weak acids have pK > 1

27. 7 8

28. Buffers are very important to biological systems
Buffering capacity is +/-1 pH unit from the pK
Different compounds have different buffering ranges

30. Practice
What is the buffer concentration and pH of a mixture of 0.042M NaH2PO4 (pK = 6.86) and M Na2HPO4?

31. Practice
What is the pH of a mixture of 75 mL of 0.042M NaH2PO4 (pK = 6.86) and 150 mL of M Na2HPO4?

32. Synthesis
You are working in the lab and need to make a physiological phosphate buffer (pH=7.2). You have the following chemicals at your disposal: Phosphoric acid, monosodium phosphate, and disodium phosphate whose corresponding pKa’s are 2.15, 6.86, and The molecular weight of each species is 98.0 g/mol, g/mol, and g/mol. Calculate the mass of each species that you would use to make a 100 mL of a 0.5M phosphate buffer at pH=7.2.
Can complete all problems at the end of chapter two except for question 11.