AP Biology 1st Semester Exam Review

Properties and Role of Water

  • Water is polar; oxygen = slightly negative, hydrogen = slightly positive.

  • Hydrogen bonds connect water molecules.

  • Water's properties (adhesion, cohesion) enable life on Earth.

  • Solvents dissolve solutes: polar solutes dissolve in polar solvents, while nonpolar solutes do not.

  • pH scale: lower pH = higher H+ concentration; acids (pH < 7) donate H+, bases (pH > 7) accept H+.

  • Buffers regulate pH, maintaining homeostasis in biological systems.

Organic Chemistry

  • Organic chemistry studies compounds containing carbon.

  • Carbon's ability to form bonds contributes to molecular diversity.

Carbohydrates and their Functions

  • Monosaccharides are single sugars; can be linear or ring-shaped.

  • Isomers have the same chemical formula but different arrangements.

  • Dehydration synthesis combines monomers, hydrolysis breaks them apart.

  • Disaccharides (e.g., sucrose, lactose) are formed through dehydration synthesis.

  • Polysaccharides, such as glycogen and cellulose, are long chains of sugars.

Lipids

  • Classes of lipids: triglycerides (energy storage), phospholipids (cell membranes), steroids (hormones).

  • Triglycerides consist of glycerol and three fatty acids; can be saturated (single bonds) or unsaturated (double bonds).

Proteins

  • Proteins are made from amino acids.

  • Amino acids consist of an amino group, carboxyl group, R group, and hydrogen.

  • Peptide bonds form between amino acids.

  • Protein structure: primary (amino acid sequence), secondary (folding), tertiary (3D shape), quaternary (multiple polypeptides).

Cell Structure

  • Prokaryotic cells lack a nucleus; eukaryotic cells have membrane-bound organelles.

  • Cell compartmentalization organizes cellular functions.

  • Important organelles: nucleus (stores DNA), mitochondria (energy production), ribosomes (protein synthesis), Golgi apparatus (processing and shipping).

Membranes

  • Cellular membranes consist of a phospholipid bilayer with embedded proteins.

  • Transport mechanisms: passive (no energy; diffusion, osmosis) and active (requires ATP).

  • Isotonic solutions are ideal for red blood cells; hypotonic solutions strengthen plant cells.

Enzymes

  • Enzymes are proteins that catalyze reactions by lowering activation energy.

  • They have specific active sites where substrates bind.

  • Factors like temperature and pH can denature enzymes and affect functionality.

Energetics: Cellular Respiration and Photosynthesis

  • Cellular respiration converts glucose into energy: C{6}H{12}O{6} + 6O{2} \rightarrow 6CO{2} + 6H{2}O + \text{ATP}.

  • Photosynthesis converts light energy into chemical energy: 6CO{2} + 6H{2}O + \text{light} \rightarrow C{6}H{12}O{6} + 6O{2}.

Cell Signaling

  • Stages: reception, signaling, and response.

  • Amplification occurs via relay proteins.

  • Apoptosis is programmed cell death, triggered by cellular signals.

Cell Cycle and Division

  • The cell cycle includes Interphase (G{1}, S, G{2}) and the Mitotic (M) phase.

  • Interphase:

    • G_{1} phase: Cell growth and normal metabolic activity.

    • S phase: DNA replication (synthesis).

    • G_{2} phase: Preparation for mitosis and final growth.

  • Mitosis phases: prophase, metaphase, anaphase, telophase (PMAT).

  • Cytokinesis Comparison:

    • Animal cells: A contractile ring of actin microfilaments forms a cleavage furrow, pinching the cell in two.

    • Plant cells: Vesicles from the Golgi apparatus move to the center and fuse to form a cell plate, which eventually becomes the new cell wall.

  • Regulation of Cell Division:

    • Stimulating Factors: External signals like growth factors (proteins released by certain cells) and internal signals such as cyclins and cyclin-dependent kinases (CDKs).

    • Inhibiting Factors:

    • Density-dependent inhibition: Crowded cells stop dividing.

    • Anchorage dependence: Most animal cells must be attached to a substratum (like a tissue) to divide.

  • Cancer vs. Normal Division:

    • Normal cells obey checkpoints and stop dividing when growth factors are depleted or density is high.

    • Cancer cells ignore checkpoints, do not exhibit density-dependent inhibition or anchorage dependence, and can divide indefinitely (immortality), potentially forming tumors.

Meiosis and Genetic Variation

  • Meiosis involves two divisions resulting in four unique haploid (n) daughter cells.

  • Meiosis I: Homologous chromosomes separate; involves crossing over and independent assortment.

  • Meiosis II: Sister chromatids separate, resulting in haploid gametes.

Statistical Analysis in Biology

  • Chi-Square (\chi^{2}) Test: Used to determine if there is a statistically significant difference between observed and expected frequencies.

    • Formula: \chi^{2} = \sum \frac{(O - E)^{2}}{E}, where O is the observed frequency and E is the expected frequency.

    • Usage: Calculate the sum of squared differences divided by expected values. Compare the result to a critical value from a table using degrees of freedom (df = n - 1).

  • Standard Deviation (s): Measures the spread of data around the mean (how dispersed the data is).

  • Standard Error (SE_{\bar{x}}): Measures how accurately a sample mean represents the population mean.

    • Formula: SE_{\bar{x}} = \frac{s}{\sqrt{n}}.

  • Error Bars:

    • Used on graphs to represent variability (often ±1 SE or ±2 SE).

    • Interpretation: If error bars overlap significantly, the difference between the means is likely not statistically significant. If they do not overlap, the difference may be statistically significant.