AP Bio Unit 1 Review Notes

AP Bio Unit 1 Review

Unit 1 Plan

• Macromolecules.

• Water properties.

• Practice questions.

• Q&A session.

Macromolecules

• Four main types: Carbohydrates, Proteins, Nucleic Acids, and Lipids.

Carbohydrates

• Elements: Carbon, Hydrogen, and Oxygen in a 1:2:1 ratio (e.g., glucose: C₆H₁₂O₆).

• Monomer: Monosaccharide.

• Polymer: Polysaccharide.

• Examples of Monosaccharides: Glucose, Fructose, Galactose (sugars)

• Disaccharides:

  • Two monosaccharides

  • Formed by dehydration reactions.

    • water removed to form new product

  • Sucrose (Glucose + Fructose).

  • Lactose (Glucose + Galactose).

  • Maltose (Glucose + Glucose).

• Glycosidic Linkage: Bond between monosaccharides.

• Polysaccharides:

  • Cellulose: Structural carbohydrate in plant cell walls.

  • Chitin: Found in fungi cell walls and exoskeletons.

  • Starch: Storage polysaccharide in plants.

  • Glycogen: Storage polysaccharide in animals (liver).

• Starch vs. Cellulose:

  • Both found in plants.

  • Starch has 1-4 alpha linkage (digestible). \ /

  • Cellulose has 1-4 beta linkage (indigestible). / \

• Termites and Cellulose Digestion:

  • Termites have a mutualistic relationship with microorganisms in their gut that break down cellulose via symbiotic relationship.

Proteins

• Elements: Carbon, Hydrogen, Oxygen, Nitrogen, and Sulfur.

• Monomer: Amino Acids.

• Hershey and Chase experiment used radioactive sulfur to track proteins.

• Amino Acid Structure:

  • Amine group (NH_2).

  • Hydrogen.

  • Carboxyl group (COOH).

  • Variable R group (20 different R groups).

• Peptide Bond:

  • Bond between carboxyl group of one amino acid and amine group of the next.

• Protein Directionality: N-terminus to C-terminus.

• Covalent bond formed throughout the long chain

• Levels of Protein Structure:

• 

  • Primary: Linear sequence of amino acids (peptide bonds).

  • Secondary: Alpha helix and beta-pleated sheets (hydrogen bonds in the backbone).

    • Carboxyl group double bonded to O making it very electronegative.

  • Tertiary: Three-dimensional structure (various bonds between R groups - covalent, ionic, van der Waals forces, hydrophobic interactions, hydrogen bonds).

  • Quaternary: Multiple polypeptides interacting (any bond between R groups of different polypeptides).

• R Groups:

  • Can be hydrophobic (nonpolar), hydrophilic (polar), or charged (positive or negative).

  • Hydrophilic fold toward aqueous solutions (exterior).

  • Hydrophobic fold toward the interior.

  • Charged fold towards exterior

  • Amine groups can take H+ from the solution becoming NH3+ (positively charged).

  • Carboxyl group losses hydrogen, it would be negative.

Nucleic Acids

• Elements: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphate.

• Hershey and Chase experiment used radioactive phosphorus to track DNA.

• Monomer: Nucleotide.

• Nucleotide Structure:

  • Phosphate group (negatively charged - PO_4^{2-}, which causes nucleic acids to be negatively charged ).

  • Nitrogenous base (Adenine, Thymine, Cytosine, Guanine, Uracil).

  • Pentose sugar (Deoxyribose or Ribose).

• Phosphodiester Linkage: Bond between nucleotides.

• DNA:

  • Has a five prime end where we have our phosphate group.

  • Has a three prime end where we're gonna have our hydroxyl group.

  • Antiparallel (5' to 3' and 3' to 5').

  • Adenine pairs with Thymine (two hydrogen bonds).

  • Cytosine pairs with Guanine (three hydrogen bonds).

• Nitrogenous Bases:

  • Purines: Adenine (A) and Guanine (G) (double ring).

  • Pyrimidines: Cytosine (C), Thymine (T, DNA), and Uracil (U, RNA) (single ring). CUT the pyramid

• DNA vs. RNA:

  • DNA: A, T, C, G; Deoxyribose sugar; Double-stranded.

  • RNA: A, U, C, G; Ribose sugar; Single-stranded.

    • Double-stranded RNA exists. single-stranded DNA exists

Lipids

• Elements: Carbon, Hydrogen, Oxygen (sometimes Phosphate in phospholipids).

• Nonpolar (due to numerous C-H bonds).

• Not a polymer (no repeating monomer).

• Types of Lipids:

  • Fats: Glycerol + 3 fatty acids (ester linkage).

    • Saturated: All single bonds, solid at room temperature (butter).

    • Unsaturated: At least one double bond, liquid at room temperature (oils).

  • Phospholipids: Phosphate group + glycerol + 2 fatty acids

    • Amphipathic (hydrophilic negative head, hydrophobic positive tails).

    • Form semipermeable bilayer in water. (outside cell is aqueous) Head - Tails - Tails - Head (inside head is aqueous)

    • Interior is hydrophobic core that inhibits things from moving through the region.

  • Steroids: Four fused rings.

    • Used for intracellular recognition, reception, and transduction, messengers.

    • Pass directly through, the membrane and bind to receptor

Water Properties

• Polarity, universal solvent, cohesion/adhesion, surface tension, high specific heat, less dense as a solid.

Polarity

• Polar covalent bonds (unequal sharing of electrons).

• Oxygen is more electronegative.

• Partial negative charge on oxygen, partial positive on hydrogen.

• Hydrogen bonds form between water molecules due to partial charges.

Universal Solvent

• Dissolves polar and charged substances.

• Partial negative oxygen binds with other polar substances.

• Partial positive hydrogen binds with other polar substances.

Cohesion and Adhesion

• Cohesion: Water molecules attracted to other water molecules.

• Adhesion: Water molecules attracted to other polar substances.

• Capillary Action:

  • Water moves up from roots to leaves.

  • Due to transpiration and water molecules adhering to other polar substances along the walls of the xylem.

Surface Tension

• Surface on top of water due to cohesion.

• Requires energy to break bonds.

Density

• Water is less dense when solid.

• Hydrogen bonds hold molecules apart in ice.

• Acts as a temperature buffer to ensure wildlife can survive and keeps temperature relatively constant.

• Density p = \frac{m}{v} which means increases volume = lesser density

High Specific Heat

• Requires a large amount of energy to change temperature. (4.184 joules / gram water).

• Coastal regions: Water absorbs heat during the day and releases it at night to regulate temperature.

• Body temperature regulation.

• Evaporative Cooling:

  • Heat breaks hydrogen bonds to cause evaporation and lowers the temperature since there is less heat.

pH

• pH = -log[H^+]

• As pH increases, hydrogen ion concentration decreases.

• As pH decreases, hydrogen ion concentration increases.

• Mitochondria: Protons pumped into the intermembrane space, pH decreases (more acidic) because you're increasing the amount of hydrogen (proton).

Practice Questions

McQ 1

• Nonpolar R groups buried in the middle, polar R groups on the surface. Which explains this?

• Answer: C. Nonpolar R groups cannot form hydrogen bonds with water, so are pushed into the middle of the protein.

MCQ 2

• Rosalind Franklin's X-ray diffraction images support what claim about DNA?

• Answer: D. The basic molecular structure is a helix.

FRQ 1

• Genetic disorder alters glucose metabolism. Describe the atoms and types of bonds in a glucose molecule.

• Answer: Carbon, Hydrogen, Oxygen. (CHO) Covalent Bonds hold them together.

FRQ 2

• Double-strand breaks occur along the DNA backbone, describe the process by which the breaks occur.

• Answer: Hydrolysis breaks the covalent bond between the sugar and the phosphate or between the nucleotides.