2 The Fundamental Building Blocks: Chemistry and Life.

2

The Fundamental Building Blocks:

Chemistry and Life

I. Introduction: Chemistry and Its Importance in Biology (Section 2.1)A. Why do we need to study chemistry?

Because you need to see what living organisms are composed of if you want to understand how they function. (City composed of bricks and mortar.) Figure 2.1

B. Also the public is increasingly responsible for health care decisions that require knowledge of chemistry (see “Science and Society”) (Interactive Activity 1, 2, or 3).

C. How do cells do anything? Chain of chemical reactions, latching on, reforming, depositing, and breaking down.

D. Look at an object, what do you see? Matter (takes up space, has weight) and energy.

II. Nature of Matter: The Atom (Section 2.2)A. Subatomic particles Figure 2.3

1. Nucleus—very small size compared to the entire atom, composed of protons (positive charge, mass) and neutrons (no charge, but mass).

2. Electrons—orbit

the nucleus (negative charge,

negligible mass).

3. Atoms are usually

electrically neutral: Number

of electrons = number of

protons.

B. Elements: Figure 2.4. Gold—pure, cannot be reduced into a simpler component substance through chemical processes.

1.Difference between iron and gold? Both are matter: Fe has 26 protons, and Au has 79 protons.

2.Atomic number = number of protons defines elements.

Periodic Table

3.One element = one atomic number.4.Elements are listed on periodic

table by number of protons: H = 1, He = 2.

5.What kind of elements are we composed of? Dirt? Figure 2.5

C. Atomic Weight and Isotopes

1. Neutrons also contribute weight, but not identity, so different forms of the same element may have different mass, called isotopes.

2. Mass number = number of protons + number of neutrons.

3. Atomic weight is the average mass number of isotopes for one element.

III. Matter Is Transformed through Chemical Bonding (Section 2.3)A. Chemical Bonding

1.Electrons—The most important particles in allowing atoms to interact so they can attach.

2.Electrons are found in distinct energy levels (shells or orbitals). Figure 2.8

3.Atoms are driven to react by a desire to become more stable (like a rock perched on a hill).

III. Matter Is Transformed through Chemical Bonding (Section 2.3)A. Chemical Bonding

4.Stability—full outer electron shell or orbital (like more energetically sound to have a full car when you commute).

5.Nonreactive elements (inert gases like argon) have full outer shells (cannot have any more passengers, so will not react).

B. Covalent Bonds—Atoms that don’t have full outer shells may want to share electrons so that they can both have full outer shells. (Interactive Activity 4)

1.Covalent bonds between two hydrogen atoms (each with one electron) and oxygen (with eight) complete the shells of all three.

2.Law of conservation of mass—matter is neither created nor destroyed.

3.Molecules = two or more atoms combined.

4.Compound = defined number of atoms in a defined spatial relationship.

5. Nonpolar versus polar covalent bonds. Figure 2.9

a) Polar = H2O, Figure 2.11. Oxygen end of the molecule is slightly negative, while the Hydrogen end is slightly positive.

b) Nonpolar = neither end is positive or negative

C. Ionic Bonds—atoms gain or lose electrons, taking on a negative or positive charge.

1.Formation of NaCl,.

2.Ions = charged atoms after losing or gaining one electron.

3.Ionic compounds = ions’ opposite charges attract one another (opposites attract)

D. Hydrogen Bonds

1. Water in solution—Polar covalent bonds in H2O generate partial negative and partial positive charge on opposite sides.

2. Partial negative end of one water attracted to partial positive end of another by a hydrogen bond. Figure 2.13

3. These H-bonds

are in DNA &

water.

V. Some Qualities of Chemical CompoundsA. Three-dimensional shape,

B. Importance of shape to biology, Figures 2-15a and 2-15b (Interactive Activity 6)

C. Solutes, Solvents, and Solutions1. Water + salt = solution. Why?

2. Polar with polar, nonpolar with nonpolar.

The End