Learning Objectives
- Understand subatomic structure, including how electron density affects an atom's ability to interact with another atom.
- Relate atomic structure to the periodic table of the elements
- Explain the discrete energy levels in which electrons orbit the nucleus of an atom.
- Compare and contrast interactions known as covalent, ionic, and hydrogen bonding.
- Explain the concept of electronegativity and how it contributes to the formation of polar and nonpolar covalent bonds.
- Describe the properties of water that make it an ideal solvent for biological reactions.
- Relate how the structure of water leads to hydrogen bonds.
- Describe how hydrogen bonding determines many properties of water.
- Describe water’s cohesive and adhesive properties.
- Explain the relevance of water’s unusual properties for living systems.
- Understand the dissociation products of water.
- Explain the nature of acids and bases, and their relationship to the pH scale.
- Understand the relationship between pH and hydrogen ion concentration, and explain how buffers maintain a stable environment
Chapter Summary
A basic understanding of chemistry is necessary to the study of biology because the two are inexorably intertwined. Living organisms are chemical machines composed of molecules that continually undergo chemical reactions to become new molecules.
Atoms are composed of protons, neutrons, and electrons. Each subatomic particle has its effect on the chemical identity and interactivity of each element with all other elements. Formation of molecules from elements depends primarily on the tendency of electrons to occur in pairs, balance positive and negative charges, and fill the outermost shell. Chemical bonds result from trading or sharing electrons; shared bonds are stronger because they require the continued close proximity of atoms to one another.
Water, a simple but elegant molecule, predominates in living organisms and is unique in the life-giving characteristics stemming from its polar nature. Water clings to other polar molecules (adhesion), as well as itself (cohesion), by forming transient hydrogen bonds. These bonds absorb thermal energy; consequently the presence of water has a moderating effect on temperature changes. It is also a powerful solvent for other polar molecules and excludes nonpolar molecules, enabling the formation of biological membranes.
PowerPoint Presentation
Virtual Lectures
1. Section 2.1: Electrons and Chemical Reactivity
2. Section 2.2: Covalent and Hydorgen Bonding
3. Section 2.3: Properties of Water
C. pH
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Animations
1. Biologically Relevant Bond Types
2. Shell Model
4. Valence Shells of the Common Elements
7. pH of Common Everyday Solutions