AP Biology Unit One Review Notes

Overview of AP Biology Unit One

  • Introduces key concepts of Unit One in AP Biology to prepare for the exam.

Importance of Water

  • Key Properties:

    • Water is essential, making up 70% of the human body. Its properties are crucial for life.

  • Hydrogen Bonding:

    • Water molecules form hydrogen bonds due to the polar nature of their bonds. Oxygen is more electronegative and attracts electrons more strongly, resulting in a partial negative charge on oxygen and a partial positive charge on hydrogen.

    • Bond angle of water is 109.5°, leading to polar bonds not cancelling out.

    • Water molecules attract each other leading to cohesion, and they can also attract other polar substances leading to adhesion.

Cohesion vs. Adhesion

  • Cohesion: Water's attraction to itself (cooperating forces).

  • Adhesion: Water's attraction to other substances (like glue).

    • Example: Water sticking to the walls of a graduated cylinder.

Hydrophilic vs. Hydrophobic Substances

  • Hydrophilic:

    • Substances that dissolve in water (polar or charged molecules).

    • E.g. Salt (NaCl) dissolving in water.

  • Hydrophobic:

    • Substances that do not dissolve in water (nonpolar molecules).

    • E.g. Oils do not mix with water due to their nonpolar nature.

  • Universal Solvent: Water can dissolve many substances due to its polar nature.

Heat Properties of Water

  • High Heat of Vaporization:

    • Takes a lot of energy to turn water from liquid to gas due to hydrogen bonds.

  • Specific Heat:

    • Water requires a significant amount of energy to change temperature, maintaining stable conditions for living organisms.

Density of Water

  • Ice is less dense than liquid water; it floats.

  • The crystal structure formed by hydrogen bonds in ice prevents lakes from freezing solid, allowing life below the surface.

Basic Concepts of Elements and Atoms

  • Elements: Substances on the periodic table defined by their atoms.

  • Atoms: Basic building blocks composed of a nucleus (protons and neutrons) and electrons.

    • Electrons are negligible in mass compared to protons and neutrons.

Importance of Carbon

  • Carbon's ability to form four strong covalent bonds makes it essential for organic compounds.

  • Hydrocarbons: Molecules made up of hydrogen and carbon.

Functional Groups in Organic Chemistry

  • Hydroxy: -OH group; forms hydrogen bonds (alcohols).

  • Methyl: -CH3; can bond with molecules.

  • Sulfhydryl: -SH; forms disulfide bridges, important in protein structure.

  • Phosphate: -PO4; part of DNA and ATP.

  • Carbonyl: C=O; important in sugars.

  • Carboxyl: -COOH; acts as an acid, releasing H+.

  • Amino Group: -NH2; basic, found in amino acids.

Types of Bonds

  • Ionic Bonds: Formed when one atom transfers electrons to another, resulting in charged ions (e.g., NaCl).

  • Covalent Bonds: Atoms share electrons; can be nonpolar (equal sharing) or polar (unequal sharing).

Intermolecular Forces (IMFs)

  • London Dispersion Forces: Weak forces due to temporary shifts in electron density, present in all molecules.

  • Hydrogen Bonds: Strong attraction between polar molecules that confer unique properties to water.

Macromolecules

  • Monomers and Polymers:

    • Macromolecules are formed from many smaller units (monomers) linked together (polymers).

  • Types of Biological Macromolecules:

    • Carbohydrates: Composed of sugars (C, H, O). Types include monosaccharides, disaccharides, and polysaccharides.

    • Proteins: Made of amino acids, structured by dehydration synthesis and hydrolysis processes.

    • Lipids: Hydrophobic molecules including triglycerides and phospholipids, vital for cell membranes.

    • Nucleic Acids: Composed of nucleotides; DNA and RNA responsible for genetic information storage.

Summary of DNA and RNA

  • DNA vs RNA:

    • DNA: Double-stranded, contains thymine (T).

    • RNA: Single-stranded, contains uracil (U) instead of thymine.

    • Directionality is important; DNA strands are anti-parallel and run in opposite directions.

Conclusion

  • Review understanding of these concepts as they form the foundation for biological processes.

  • Importance of preparation and understanding underlying principles for AP Biology exam success.