Glycolysis: cytoplasm. Net 2 ATP, 2 NADH, 2 pyruvate. Pyruvate oxidation: mitochondrial matrix. 2 acetyl-CoA, 2 NADH, 2 CO₂. Krebs (×2 turns): mitochondrial matrix. 2 ATP, 6 NADH, 2 FADH₂, 4 CO₂.
B. O₂ accepts electrons at Complex IV and combines with H+ to form H₂O.
B. Photosystems II/I are embedded in thylakoid membranes; water-splitting yields O₂ in the lumen; ATP and NADPH are made for the Calvin cycle.
Substrate-level: direct enzymatic transfer of a phosphate from a high-energy substrate to ADP (e.g., in glycolysis steps 7,10 and one Krebs step). Oxidative phosphorylation: ATP synthesis using energy from the H+ gradient generated by the ETC; depends on O₂. Yields most of the cell's ATP (~26 of ~30).
(a) glycolysis. (b) acetyl-CoA. (c) chlorophyll a (with chlorophyll b and carotenoids as accessory pigments).
B. H+ flow back through the synthase is blocked; gradient builds up; eventually ETC also stalls (no proton-pumping driving force) and O₂ consumption falls.
Glycolysis: 2 ATP (substrate-level) + 2 NADH (cytosolic, ~1.5 each via glycerol-3-P shuttle) = 2 + 3 = 5. Pyruvate oxidation: 2 NADH × 2.5 = 5. Krebs: 2 ATP + 6 NADH × 2.5 + 2 FADH₂ × 1.5 = 2 + 15 + 3 = 20. Total = 5 + 5 + 20 = 30 ATP (or 32 with malate-aspartate shuttle).
(a) Collapses gradient — DNP carries H+ across membrane bypassing synthase. (b) ATP drops sharply. (c) Heat rises (energy from electron transport dissipates as heat instead of being captured as ATP). (d) O₂ consumption increases (ETC runs faster trying to pump H+ that DNP keeps draining). Historically marketed for weight loss; banned due to fatal hyperthermia.
IV: light intensity (e.g., distance to lamp 10, 30, 60 cm) — quantify with lux meter. DV: O₂ production rate (count bubbles/min, or measure dissolved O₂ probe). Controlled: temperature (water bath), CO₂ supply (NaHCO₃ buffer), elodea length, light wavelength, time. Hypothesis: rate increases with intensity until light saturation. Replicate ≥3 trials.
Outer membrane; intermembrane space (high H+); inner membrane (folded into cristae) — site of ETC complexes I–IV and ATP synthase; matrix (low H+) — site of pyruvate oxidation and Krebs. ETC pumps H+ from matrix to intermembrane space; H+ flows back through ATP synthase into matrix → ATP.
Aerobic: ~30 ATP/glucose, requires O₂, end products CO₂ + H₂O, location cytoplasm + mitochondria. Lactic fermentation: 2 ATP/glucose, no O₂, end product lactate (and NAD+ regenerated), location cytoplasm only. Common stage: glycolysis.
Photosynthesis: 6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂; respiration is the reverse. Plants capture solar energy as chemical bonds; respiration releases that energy to make ATP. Producers fix carbon; consumers and decomposers respire it back to CO₂. The cyclic exchange of CO₂ and O₂ links all aerobic life.
(i) ETC halts at Complex IV; no electrons can reach O₂; entire chain backs up. (ii) Oxidative phosphorylation stops; only 2 ATP/glucose from glycolysis remain (lactate accumulates → metabolic acidosis). (iii) Heart and brain rely heavily on continuous oxidative phosphorylation; they have minimal glycolytic capacity, so ATP collapse is rapid → cardiac arrest and unconsciousness within minutes.
Jogging (aerobic): O₂ supply meets demand; muscles use oxidative phosphorylation of glucose and fatty acids → CO₂ + H₂O + ATP. Sprint: O₂ demand exceeds supply (anaerobic threshold). Cells run glycolysis hard; pyruvate → lactate via lactate dehydrogenase to regenerate NAD+. Lactate accumulates (burning sensation). Breathing rate ↑ to repay "oxygen debt" — lactate is later transported to the liver (Cori cycle) and re-converted to glucose.
Yeast: glucose → 2 ethanol + 2 CO₂ + 2 ATP. Crops (corn, sugarcane) → starch → glucose → fermentation → distillation → ethanol fuel (E10/E85). Advantages: renewable, lower net CO₂ if plants reabsorb (carbon-cycle neutral in theory). Drawbacks: competes with food crops; energy-intensive distillation; land/water use; some life-cycle analyses show modest net energy gain.