Respiration — Telangana (SSC) Class 10 Science Solutions (Free)

Respiration: Process of breaking down organic molecules (glucose) to release energy (ATP) for cellular activities. Aerobic respiration: Occurs in presence of oxygen Organism: All animals, most plants, most microorganisms Location: Mitochondria (mainly), some in cytoplasm Substrate: Glucose (C₆H₁₂O₆) Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (38 ATP) Products: CO₂, H₂O, energy Anaerobic respiration: Occurs without oxygen Organism: Some bacteria, fungi (yeast), muscle cells during intense activity Location: Cytoplasm only Substrate: Glucose Equation (in yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + energy (2 ATP) Equation (in muscle): C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + energy (2 ATP) Products: Ethanol/lactic acid, CO₂, energy Key difference: Aerobic releases 19x more ATP than anaerobic

Step 1 - Glycolysis (cytoplasm): • Glucose (6C) → 2 Pyruvate (3C) + 2 ATP + 2 NADH • No oxygen required • Occurs in all cells Step 2 - Krebs Cycle/Citric Acid Cycle (mitochondrial matrix): • Pyruvate → Acetyl-CoA (enters cycle) • Each glucose → 2 turns of cycle • Produces: 4 CO₂, 2 ATP, 6 NADH, 2 FADH₂ • Oxidizes carbons completely to CO₂ Step 3 - Electron Transport Chain (inner mitochondrial membrane): • NADH + FADH₂ release electrons • Electrons pass through protein complexes (I, II, III, IV) • Energy pumps H⁺ ions across membrane • Creates proton gradient → ATP synthase driven • Final electron acceptor: Oxygen (O₂) → water (H₂O) • Produces: ~32 ATP Total ATP: ~38 ATP per glucose

Human respiratory system organs: 1. Nostrils/Nose: Filter, warm, humidify air 2. Nasal cavity: Lined with mucous membrane; warms air 3. Pharynx: Common passage for food and air 4. Larynx: Voice box; contains vocal cords 5. Trachea: Windpipe; supported by cartilage rings; branches into bronchi 6. Bronchi: Right (3 lobes) and left (2 lobes) main branches 7. Bronchioles: Further divisions of bronchi 8. Alveoli: Tiny air sacs (300 million); site of gas exchange; surrounded by capillaries 9. Lungs: Main respiratory organs; contain alveoli 10. Diaphragm: Muscle controlling breathing; contracts → inhalation Functions of respiratory system: 1. Gas exchange: O₂ intake, CO₂ removal 2. Respiration: Aerobic respiration in mitochondria 3. Temperature regulation: Heat loss via exhaled breath 4. Vocalization: Speaking, singing 5. Defense: Cilia and mucus trap pathogens

Breathing mechanism: Inhalation (breathing in): • Diaphragm contracts → flattens → moves downward • Intercostal muscles (external) contract → ribcage moves up and outward • Thoracic cavity volume increases • Pressure inside lungs decreases (below atmospheric) • Air rushes in along pressure gradient • Duration: ~2 seconds Exhalation (breathing out): • Diaphragm relaxes → curves up → moves upward • Intercostal muscles (external) relax → ribcage moves down and inward • Thoracic cavity volume decreases • Pressure inside lungs increases (above atmospheric) • Air rushes out along pressure gradient • Duration: ~3 seconds Cause of air movement: Pressure differences (Boyle's Law): P₁V₁ = P₂V₂ • Volume increase → pressure decrease → air enters • Volume decrease → pressure increase → air exits Breathing rate: 12-20 breaths/minute at rest

Gas exchange in lungs (external respiration): • Alveoli (capillaries) surrounded by air (high O₂, low CO₂) • Blood from heart arrives with low O₂, high CO₂ • O₂ diffuses from alveoli → blood capillaries • CO₂ diffuses from blood → alveoli • Oxygenated blood returns to heart → distributed to body Gas exchange in tissues (internal respiration): • Tissue cells carrying out respiration (consuming O₂, producing CO₂) • Blood capillaries arrive with high O₂, low CO₂ • O₂ diffuses from blood → cells • CO₂ diffuses from cells → blood • Deoxygenated blood returns to heart → sent to lungs Role of hemoglobin: 1. Protein in RBCs; contains iron (Fe²⁺) 2. Binds O₂ loosely in lungs (high O₂) → oxyhemoglobin (bright red) 3. Releases O₂ in tissues (low O₂) → hemoglobin (dark red) 4. Carries ~20.8 mL O₂ per 100 mL blood 5. Also carries some CO₂ (minor role) 6. Affinity for O₂ increases at low CO₂, high pH (favorable for loading in lungs)

Consequences of oxygen deficiency: 1. Reduced ATP production: • Aerobic: 38 ATP per glucose • Anaerobic: 2 ATP per glucose • 19x less energy → cellular exhaustion 2. Lactic acid accumulation: • Glucose → lactic acid (instead of CO₂ + H₂O) • Lactic acid lowers pH → muscle fatigue • Causes muscle soreness (DOMS) 3. Cellular dysfunction: • Brain: Loss of consciousness after 4-6 minutes • Heart: Arrhythmia, cardiac arrest • Other organs: Progressive damage 4. Death if prolonged Anaerobic respiration in muscle cells: • During intense exercise: O₂ demand > O₂ supply • Muscles switch to anaerobic metabolism • Glucose → Pyruvate → Lactate (lactic acid) • Equation: C₆H₁₂O₆ → 2C₃H₆O₃ + 2 ATP • Lactate accumulates → blood pH drops → muscle fatigue • Post-exercise: O₂ debt (EPOC) repays lactate oxidation • Recovery: Lactate converted back to glucose (Cori cycle) in liver

Differences: 1. Purpose: Animals: Only respiration (for energy) Plants: Respiration + photosynthesis; respiration uses glucose from photosynthesis 2. Organelles: Animals: Mitochondria (main site) Plants: Mitochondria + chloroplasts (some glucose from photosynthesis) 3. Oxygen exchange (apparent): Animals: Net O₂ consumption (24/7) Plants: Photosynthesis produces more O₂ than respiration consumes (daytime) 4. Intensity: Animals: Continuous, high rate for movement/thermoregulation Plants: Continuous, slow rate (no movement, no heat production) Similarities: 1. Basic process: Both break glucose → ATP + CO₂ + H₂O 2. Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP (same in both) 3. Location: Both occur in mitochondria 4. Energy: Both use aerobic respiration (when O₂ available)