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Lake Tahoe Community College
Introduction to Cell and Molecular Biology
Bio 110
Instructor: Sue Kloss
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Chapter 2
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I. Atoms and Molecules
A. Emergent properties – atoms and molecules
B. Life requires about 25 chemical elements
C. Elements combine to form compounds - 2 or more elements in fixed ratio
1. table salt is NaCl; iodized (fig. 2.4)
2. Water
D Atoms consist of protons, neutrons and electrons
1. atom is the smallest unit of matter
2. subatomic particles make up the atom.
3. Differences in elements
4. isotopes - different numbers of neutrons so mass changes
E. Electron arrangement determines chemical properties of atom
1. electrons determine how an atom behaves
2. electrons vary in energy
3. electrons occur at certain energy levels
F. Ionic bonds are attractions between ions of opposite charges
1. ion = loss or gain of electron
2. ions with opposite charges attract each other
3. resulting compound is electrically neutral
4. sodium and chloride ions are always present in 1:1 ratio
G. Covalent bonds = sharing of electrons in outer shell
1. molecule
2. single covalent bond
4. double bond
5. H2 and O2 are molecules but not compounds
H. Chemical reactions rearrange matter
1. chemical reactions
2. reactants
3. product
4. 2 H2 +O2 = H2O
II. Properties of water
A. water is a polar molecule
B. Water’s polarity leads to H bonding
C. Hydrogen bonds make liquid water cohesive
1. H bonds last for only a few trillionths of a second
2. cohesion and adhesion
3. surface tension
D. Hydrogen bonds of water moderate temperature
1. heat
2. temperature
E. Ice is less dense than water
F. water is a versatile solvent
1. solution
2. solvent
3. solute
4. aqueous solution
G. The chemistry of life is sensitive to acid and basic conditions
1. some water molecules break apart naturally in water
2. ions formed are called hydrogen (H+) and hydroxide (OH-) ions
3. for life chemistry, proper balance of these ions is necessary
4. the more acidic a solution, the more H+ ions. Acids are substances that donate H+
5. in your stomach, HCl donates H+ ions when in solution
6. a base (or alkali) accepts H+ and removes them from solution
Lesson Objectives/Homework Questions Ch. 2
1. List and briefly describe levels of organization from an actin molecule to an insect flight muscle, to show emergent
properties.
2. Define matter, an element, and a trace element.
3. Define a compound and explain how compounds in living organisms are different from compounds in nonliving things.
4. Describe the structure of an atom.
5. Distinguish between atomic number and atomic weight or mass number of an atom.
6. Define an isotope and explain what makes some isotopes radioactive. Why are isotopes important in biology?
7. Explain how the electron configuration of an atom influences its behavior.
8. Distinguish among polar covalent, non polar covalent and ionic bonds and note their relative strengths and functions.
9. Describe the special properties of water that make it vital to living systems.
10. Define a solute, a solvent and a solution.
11. Explain how acids and bases affect the hydrogen ion concentration of a solution.
12. Explain the basis for the pH scale.
13. Explain how buffers work.
14. Define a chemical reaction and distinguish between reactants and products.