1. Chapter 2 The Chemistry of Life

2. All Matter Consists of Elements Made of Atoms
Atoms contain:
Protons: positive charge; have mass
Neutrons: no charge; have mass
Electrons: negative charge; negligible mass

3. FIGURE 2.1
An atom of helium, showing protons and neutrons in the nucleus and electrons occupying a region around the nucleus.

5. TABLE 2.1
REVIEW OF SUBATOMIC PARTICLES

6. Chemical bonds form between the atoms of a compound
The atoms in a compound are held together by covalent, ionic or hydrogen bonds

7. FIGURE 2.7
Atoms of hydrogen, carbon, and oxygen. Each of the concentric circles around the nucleus represents a shell occupied by electrons.

8. Covalent Bonds Covalent bonds are the strongest bonds
Form when two or more atoms share the electrons in their outer shells

9. Single Covalent Bonds FIGURE 2.8a
Covalent bonds form when electrons are shared between atoms. Shown here are examples of single, double, and triple covalent bonds. For each example, the structural formula is shown on the far right.

10. Double Covalent Bonds FIGURE 2.8b
Covalent bonds form when electrons are shared between atoms. Shown here are examples of single, double, and triple covalent bonds. For each example, the structural formula is shown on the far right.

11. Triple Covalent Bonds FIGURE 2.8c
Covalent bonds form when electrons are shared between atoms. Shown here are examples of single, double, and triple covalent bonds. For each example, the structural formula is shown on the far right.

12. Ionic Bonds
An ion is an atom or group of atoms with a positive or negative electrical charge
Ionic bonds, weaker than covalent bonds, result from the attraction of oppositely charged ions, rather than shared electrons

13. FIGURE 2.9
An ionic bond involves the transfer of electrons between atoms. Such a transfer creates oppositely charged ions that are attracted to one another.

14. Hydrogen Bonds
Hydrogen bonds are the attraction formed between a slightly positively charged hydrogen atom and another slightly negatively charged atom
Many hydrogen bonds can collectively add up to formation of tightly bound molecules, e.g., DNA double helix

15. Hydrogen Bonds
Hydrogen bonds account for the unique properties of water and the geometric shape of many biological molecules

16. FIGURE 2.10a
The hydrogen bonds of water

17. FIGURE 2.10b
The hydrogen bonds of water

18. TABLE 2.2
REVIEW OF CHEMICAL BONDS

19. Acids and Bases Acids and bases react differently to water
Acids release hydrogen ions (H+) when placed in water and bases produce hydroxide ions (OH-) when added to water

20. The pH Scale: Each unit equals A 10 fold change In H+ concentration
FIGURE 2.12
The pH scale and the pH of some body fluids and other familiar substances.

21. Acids and Bases
The lower the pH on the pH scale, the greater the acidity and the higher the pH, the more basic a solution

22. TABLE 2.3
REVIEW OF THE CHARACTERISTICS OF ACIDS AND BASES

23. Synthesis and Hydrolysis of Polymers
Biological macromolecules are the giant molecules of life (proteins, nucleic acids, lipids, carbohydrates)
They are long chains called polymers made of repeating units called monomers

24. Synthesis of Polymers
When polymers are made, water is removed and the reaction is called a dehydration synthesis

25. FIGURE 2.13a
Formation and breaking apart of polymers.

26. Hydrolysis of Polymers
Conversely, when the same molecules are broken apart, water is added and the reaction is a hydrolysis

27. FIGURE 2.13b
Formation and breaking apart of polymers.