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BIOL Exam 1 Quick-Review Notes

Energy-Carrier Molecules

  • ATP: stores energy in the terminal phosphate bond
    • \text{ADP}\xrightarrow{\text{+ energy}}\text{ATP} (endergonic)
    • \text{ATP}\xrightarrow{\text{release P}}\text{ADP} (exergonic; powers cellular work)
  • NAD\textsuperscript{+}/NADH: electron (energy) carrier
    • Oxidation: \text{NADH}\rightarrow\text{NAD}^{+} (loses \text{H/e}^{-}, lower energy)
    • Reduction: \text{NAD}^{+}\rightarrow\text{NADH} (gains \text{H/e}^{-}, higher energy)

Cellular Respiration (aerobic)

  • Overall: glucose + \text{O}2 \rightarrow \text{CO}2 + H\textsubscript{2}O + ATP
  • Steps & key outputs per glucose
    • Glycolysis (cytosol): glucose \rightarrow 2 pyruvate, 2 ATP, 2 NADH
    • Pyruvate oxidation (matrix): 2 pyruvate \rightarrow 2 acetyl-CoA, 2 NADH, 2 \text{CO}_2
    • Citric acid cycle (matrix): 2 acetyl-CoA \rightarrow 4 \text{CO}_2, 6 NADH, 2 FADH\textsubscript{2}, 2 GTP/ATP
    • Oxidative phosphorylation (inner membrane)
    • ETC: NADH/FADH\textsubscript{2} oxidized; e\textsuperscript{−} flow pumps H\textsuperscript{+}
    • Chemiosmosis: H\textsuperscript{+} through ATP synthase \rightarrow \approx 28\text{–}30 ATP; O\textsubscript{2} is final e\textsuperscript{−} acceptor \rightarrow H\textsubscript{2}O
  • Anaerobic: glycolysis + fermentation (regenerates \text{NAD}^{+}); yields only 2 ATP

Photosynthesis (plants)

  • Overall: light energy + \text{H}2\text{O} + \text{CO}2 \rightarrow O\textsubscript{2} + sugars
  • Light reactions (thylakoid)
    • Chlorophyll absorbs red/blue light, excites e\textsuperscript{−}
    • e\textsuperscript{−} flow via photosystems pumps H\textsuperscript{+}; produces ATP & NADPH
    • H\textsubscript{2}O splits to replace e\textsuperscript{−}; releases O\textsubscript{2}
  • Carbon fixation (stroma; Calvin cycle)
    • Uses ATP & NADPH + \text{CO}_2 to form carbohydrates; regenerates starting RuBP

Cell Signaling Essentials

  • Distance types: juxtacrine, autocrine, paracrine, endocrine (hormone via blood)
  • Receptors
    • Intracellular: small, non-polar ligands
    • Membrane: ligand-gated ion channel, protein kinase receptor (dimerize & autophosphorylate), G-protein-coupled receptor
  • Signal transduction
    • Conformational change initiates cascade; amplifies signal
    • Second messenger example: cyclic AMP (cAMP)
    • Epinephrine/glucagon ↑ adenylyl cyclase → ↑ cAMP → ↑ blood glucose
    • Insulin activates phosphodiesterase → ↓ cAMP → ↓ blood glucose

Cell Cycle & Mitosis

  • Interphase: \text{G}1 (growth) → \text{S} (DNA replication) → \text{G}2 (prep)
  • Mitosis (PPMAT)
    1. Prophase: chromatin condenses
    2. Prometaphase: nuclear envelope breaks; spindle attaches at kinetochores
    3. Metaphase: chromosomes align mid-cell
    4. Anaphase: sister chromatids separate
    5. Telophase: nuclei re-form; cytokinesis splits cell
  • Result: 1 diploid parent → 2 identical diploid daughters

Meiosis & Genetic Variation

  • Purpose: generate haploid gametes; introduce diversity
  • Single DNA replication, two divisions
    • Meiosis I: homologs pair, crossing over (prophase I), independent assortment (metaphase I), homologs separate → 2 haploid cells (chromosomes still duplicated)
    • Meiosis II: sister chromatids separate (resembles mitosis) → 4 unique haploid gametes
  • Key terms
    • Homologous chromosomes: same genes, different alleles
    • Sister chromatids: identical copies after S phase

Chromosome Number Abnormalities

  • Trisomy: extra single chromosome (e.g., Down syndrome = trisomy 21)
  • Monosomy: missing single chromosome (viable only as X0 Turner syndrome)
  • Polyploidy / Triploidy: entire extra set(s) of chromosomes; usually lethal in humans