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