Study Guide EXAM #1: Key Concepts in the Study of Life, Chemical Foundations of Life, Biological Macromolecules, and the Cell
1. Key Concepts in the Study of Life
Characteristics of Life
• Cellular Organization: All living organisms are composed of cells, which can be unicellular (e.g., bacteria) or multicellular (e.g., plants,
animals).
• Metabolism: The set of chemical reactions that occur within an organism, including:
• Catabolism: Breakdown of molecules to release energy (e.g., digestion).
• Anabolism: Building complex molecules from simpler ones, using energy (e.g., protein synthesis).
• Homeostasis: The ability of organisms to maintain a stable internal environment (e.g., temperature, pH, water balance).
• Growth and Development: Growth involves an increase in size or cell number, and development involves changes in the organism over time.
• Reproduction: The ability to reproduce offspring (asexual or sexual).
• Response to Stimuli: Organisms respond to environmental changes (e.g., light, temperature).
• Adaptation: Changes in organisms over generations that make them better suited to their environment.
• Heredity: Genetic information is passed from one generation to the next via DNA.
Levels of Biological Organization
Atoms → Molecular: Molecules → Cellular: Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities →
Ecosystems → Biosphere
2. Chemical Foundations of Life
Atoms and Molecules
• Atoms: The basic units of matter consisting of protons, neutrons, and electrons.
• Elements: Substances composed of only one type of atom, like carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and
sulfur (S), which are the key elements in biological molecules.
• Molecules: Two or more atoms bonded together.
Types of Chemical Bonds
• Covalent Bonds: Atoms share electrons to form a bond (e.g., H₂O). This bond is strong and common in biological molecules.
• Ionic Bonds: One atom donates an electron to another, resulting in positively and negatively charged ions (e.g., NaCl).
• Hydrogen Bonds: Weak bonds that form between the hydrogen atom of one molecule and the electronegative atom (e.g., oxygen) of another
molecule (important for water’s properties and DNA structure).
Water and Its Properties
• Polar Molecule: Water has a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms.
• Solvent: Water dissolves many substances, making it the universal solvent.
• Cohesion: Water molecules stick together due to hydrogen bonding (e.g., surface tension).
• Adhesion: Water molecules cling to other substances (important for capillary action).
• High Specific Heat: Water resists temperature change, helping organisms regulate body temperature.
• Evaporative Cooling: Water absorbs heat when it evaporates, cooling the surface (important for thermoregulation).
pH and Buffers
• pH: A measure of the acidity or alkalinity of a solution (0 to 14 scale; 7 is neutral, below 7 is acidic, above 7 is basic).
• Acids: Donate H⁺ ions (e.g., HCl).
• Bases: Accept H⁺ ions (e.g., NaOH).
• Buffers: Help maintain a stable pH by absorbing or releasing H⁺ ions.
3. Biological Macromolecules
Carbohydrates
• Monomers: Monosaccharides (simple sugars like glucose, fructose).
• Polymers: Polysaccharides (long chains of monosaccharides). Examples:
• Starch: Energy storage in plants.
• Glycogen: Energy storage in animals.
• Cellulose: Structural support in plant cell walls.
•Functions: Energy storage, quick energy source, structural components.
