Cell Structure:
  Prokaryotic: No membrane-bound nucleus, no membrane organelles
    Examples: bacteria, blue-green algae (cyanobacteria)
    70S ribosomes, circular DNA (no histones), cell wall of peptidoglycan

  Eukaryotic: Membrane-bound nucleus, membrane organelles
    Examples: plant cells, animal cells, fungi, protists
    80S ribosomes (except mitochondria/chloroplast — 70S)
    Linear DNA with histones

Key organelles:
  Mitochondria:  "Powerhouse" — ATP synthesis (oxidative phosphorylation)
                 Double membrane, own DNA, 70S ribosomes
                 Number highest in cells with high energy needs (liver, muscle)

  Chloroplast:   Photosynthesis — light reactions in thylakoid, dark in stroma
                 Double membrane, own DNA, 70S ribosomes
                 Only in plant cells and algae

  Ribosome:      Protein synthesis (translation)
                 80S (cytoplasm) = 60S + 40S subunits
                 70S (mitochondria, chloroplast, prokaryotes) = 50S + 30S

  Golgi complex: Post-translational modification, packaging, secretion
                 Cis face (receives from ER) → Trans face (ships out)
                 Makes cell wall material in plants

  Lysosome:      "Suicide bag" — digestive enzymes, intracellular digestion
                 Only in animal cells (NOT plant cells)
                 pH 5 (acidic) — optimal for hydrolytic enzymes

  Nucleus:       Contains DNA, site of transcription
                 Double membrane with nuclear pores
                 Nucleolus: rRNA synthesis

Overall equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (light energy)

Light Reactions (Thylakoid membrane):
  PS II (P680) → absorbs light, water splits (O₂ released), electrons flow
  Electron transport chain → creates proton gradient
  PS I (P700) → excited again, NADP⁺ reduced to NADPH
  ATP synthase → ADP + Pi → ATP (photophosphorylation)
  Output: ATP + NADPH + O₂

Calvin Cycle / Dark Reactions (Stroma):
  CO₂ fixation: CO₂ + RuBP → 2 × 3-PGA (enzyme: RuBisCO)
  Reduction: 3-PGA → G3P (uses ATP + NADPH)
  Regeneration: G3P → RuBP (uses ATP)
  Net: 3CO₂ → 1 molecule G3P (need 6 turns for 1 glucose)

C₃ plants: 3-PGA (3-carbon compound) first stable product
  Examples: wheat, rice, potato, sunflower
  More common, less efficient in hot/dry conditions

C₄ plants: OAA (4-carbon) first product, Kranz anatomy
  Examples: maize, sugarcane, sorghum
  Minimal photorespiration, efficient in hot/sunlight

CAM plants: Stomata open at night, CO₂ stored as malate
  Examples: cacti, pineapple, agave
  Extreme drought adaptation

Mouth: Salivary amylase (ptyalin) → starch to maltose (pH 6.8)
       Mucus lubricates food; chewing breaks down mechanically

Stomach: HCl (pH 1-2) activates pepsinogen → pepsin
         Pepsin: proteins → peptides
         Gastric lipase: fats (minor digestion)
         Chyme = acidic food mass leaving stomach

Small Intestine (main absorption site):
  Duodenum: bile (liver, stored in gall bladder) emulsifies fats
            pancreatic juice: amylase, lipase, trypsin, chymotrypsin
  Jejunum + Ileum: villi and microvilli (brush border) → maximum absorption
            Final enzymes: maltase, lactase, sucrase (disaccharidases)
            Peptidases → amino acids
            Amino acids + glucose + water → blood (portal vein)
            Fatty acids + glycerol → lacteals (lymph)

Large Intestine:
  Absorption of water, minerals
  Formation of feces
  Bacteria produce Vitamin K, Vitamin B₁₂