BackUnit 6 Review: Water, Biomolecules, and Biological Reactions
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Water Modeling & Investigation
Water with Water
Water molecules interact with each other through hydrogen bonding. Each water molecule can form up to four hydrogen bonds with neighboring water molecules due to its polar nature.
Key Point: The polarity of water (partial negative charge on oxygen, partial positive on hydrogen) allows for strong intermolecular attractions.
Key Point: Hydrogen bonds are responsible for water's high boiling point, surface tension, and solvent abilities.
Example: Water droplets form beads on a surface due to cohesion from hydrogen bonding.
Water with Sodium Chloride
When sodium chloride (NaCl) dissolves in water, the polar water molecules surround the positive sodium ions (Na+) and negative chloride ions (Cl-), separating them from the crystal lattice.
Key Point: Water acts as a solvent for ionic compounds due to its polarity.
Key Point: The process of dissolving is called hydration or solvation.
Example: Table salt dissolving in water is a common demonstration of this property.
Water and Ethane vs. Water and Ethanol
Water and ethanol mix readily due to hydrogen bonding, while water and ethane do not mix because ethane is nonpolar and cannot form hydrogen bonds with water.
Key Point: Like dissolves like: polar substances dissolve in polar solvents, nonpolar in nonpolar.
Key Point: Ethanol (C2H5OH) has a polar hydroxyl group, allowing hydrogen bonding with water.
Key Point: Ethane (C2H6) is nonpolar and does not interact favorably with water.
Example: Alcohol and water mix completely, but oil (nonpolar) and water separate.
pH Coloring & Lab
This lab explores the concept of pH, which measures the concentration of hydrogen ions (H+) in a solution.
Key Point: pH is defined as .
Key Point: Acids have pH < 7, bases have pH > 7, and neutral solutions have pH = 7.
Example: Lemon juice (acidic), soap (basic), and pure water (neutral).
Biological Reactions: Cut and Paste Biomolecules Investigation
This activity focuses on the structure and function of biomolecules, including carbohydrates, proteins, lipids, and nucleic acids.
Key Point: Biomolecules are composed of specific monomers: monosaccharides (carbohydrates), amino acids (proteins), fatty acids and glycerol (lipids), nucleotides (nucleic acids).
Key Point: The arrangement and bonding of these monomers determine the properties and functions of the resulting polymers.
Example: Glucose units form starch (a carbohydrate polymer).
Biological Reactions: Hydrolysis Modeling
Hydrolysis is a chemical reaction in which water is used to break down polymers into monomers.
Key Point: Hydrolysis reactions are essential for digestion and metabolism.
Key Point: The general equation for hydrolysis of a polymer is:
Example: Proteins are hydrolyzed into amino acids during digestion.
Monomers & Polymers of the 4 Main Biomolecules
Biological macromolecules are formed by linking monomers into polymers through dehydration synthesis and broken down by hydrolysis.
Biomolecule | Monomer | Polymer | Example |
|---|---|---|---|
Carbohydrates | Monosaccharide | Polysaccharide | Starch, Glycogen |
Proteins | Amino Acid | Polypeptide | Enzymes, Hemoglobin |
Lipids | Fatty Acid, Glycerol | Triglyceride | Fats, Oils |
Nucleic Acids | Nucleotide | Polynucleotide | DNA, RNA |
Key Point: Dehydration synthesis joins monomers by removing water; hydrolysis breaks polymers by adding water.
Example: DNA is a polymer of nucleotides.
