Life Processes Revision Notes - Class 10 Science

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📌 Key Points

Life processes: Nutrition, Respiration, Transportation, Excretion, Growth, Reproduction
Autotrophic nutrition: Green plants, algae (photosynthesis). Heterotrophic: Animals, fungi (digestion)
Photosynthesis equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Light reactions (thylakoid): Produce ATP, NADPH, O₂. Dark reactions (stroma): Use ATP/NADPH to fix CO₂ → glucose
Aerobic respiration: 38 ATP per glucose. Glycolysis (cytoplasm, 2 ATP) → Pyruvate Oxidation → Krebs cycle (2 ATP) → ETC (34 ATP)
Anaerobic respiration: Only 2 ATP per glucose. In animals: Pyruvate → Lactic acid. In microbes: Pyruvate → Ethanol + CO₂
Glycolysis occurs in cytoplasm: Glucose → 2 Pyruvate (2 ATP, 2 NADH)
Krebs cycle (mitochondrial matrix): Acetyl CoA oxidation → 6 NADH, 2 FADH₂, 2 ATP, CO₂
ETC (inner mitochondrial membrane): NADH (3 ATP), FADH₂ (2 ATP). O₂ is final electron acceptor
Xylem: Dead cells, transports water + minerals (upward), root pressure + capillary action + transpiration pull
Phloem: Living cells, transports glucose (bidirectional), osmotic pressure gradient (turgor pressure)
Blood: 55% plasma + 45% cells (RBC, WBC, Platelets). RBC carries O₂, WBC fights disease, Platelets clot
Pulmonary circulation: Right heart → Lungs (deoxygenated). Systemic circulation: Left heart → Body (oxygenated)
Excretion in plants: CO₂ via stomata, water via transpiration. In animals: Kidneys (urea), lungs (CO₂), skin (sweat)
Kidney function: Ultrafiltration (Bowman's) → Selective reabsorption (PCT) → Tubular secretion → Urine

📘 Important Definitions

Life Processes

Activities that maintain life in organism: nutrition (food intake), respiration (energy release), transportation (nutrient distribution), excretion (waste removal), growth, reproduction

Autotrophic Nutrition

Organisms manufacture their own food (photosynthesis). E.g., green plants, algae. Self-feeding.

Heterotrophic Nutrition

Organisms depend on other organisms for food. E.g., animals (holozoic), fungi (saprophytic), tapeworm (parasitic).

Photosynthesis

Green plants manufacture glucose using CO₂, H₂O, and sunlight. Light reactions → ATP/NADPH. Dark reactions → glucose.

Respiration

Breakdown of glucose to release energy as ATP. Aerobic (with O₂, 38 ATP) or anaerobic (without O₂, 2 ATP).

Glycolysis

Breakdown of glucose to pyruvate in cytoplasm. Produces 2 ATP and 2 NADH. First stage of both aerobic and anaerobic respiration.

Krebs Cycle

Oxidation of acetyl CoA in mitochondrial matrix. Produces NADH, FADH₂, ATP. Also called citric acid cycle or TCA cycle.

Xylem

Dead vascular tissue transporting water and mineral nutrients from roots to leaves. Provides support. Unidirectional transport.

Phloem

Living vascular tissue transporting glucose and organic compounds from source to sink. Bidirectional. Uses osmotic pressure.

Excretion

Removal of metabolic wastes from body: CO₂ (lungs), urea (kidneys), sweat (skin). Different from egestion (feces).

Digestion

Breakdown of complex food molecules by enzymes. Carbs → glucose, proteins → amino acids, fats → fatty acids + glycerol.

🔢 Formulas & Laws

Photosynthesis Equation

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Light reactions produce ATP/NADPH. Dark reactions (Calvin cycle) use them

Aerobic Respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 2880 kJ (38 ATP)

Glycolysis (2) + Pyruvate oxidation (0) + Krebs (2) + ETC (34) = 38 ATP

Anaerobic Respiration (Animals)

C₆H₁₂O₆ → 2 Lactic acid + 2 ATP

Only 2 ATP produced. Occurs in muscles during intense exercise

Glycolysis

Glucose → 2 Pyruvate + 2 ATP + 2 NADH

First stage, occurs in cytoplasm. No oxygen required

ATP Production (Aerobic)

Glycolysis (2) + Pyruvate Ox (0) + Krebs (2) + ETC (34) = 38 ATP

NADH produces 3 ATP, FADH₂ produces 2 ATP in ETC

Magnification of Enzyme

Rate with enzyme / Rate without enzyme = 10⁶ to 10¹⁷

Enzymes speed up reactions dramatically without being consumed

⚠️ Common Mistakes

✗ Wrong: Confusing photosynthesis with respiration

✓ Correct: Photosynthesis: Makes glucose (anabolic, energy storage). Respiration: Breaks glucose (catabolic, energy release)

✗ Wrong: Thinking dark reactions need no light

✓ Correct: Dark reactions don't directly need light but indirectly depend on ATP and NADPH from light reactions

✗ Wrong: Confusing aerobic and anaerobic locations

✓ Correct: Glycolysis in cytoplasm (both). Krebs cycle and ETC in mitochondria (aerobic only)

✗ Wrong: Thinking all ATP from one stage

✓ Correct: Aerobic: Glycolysis 2 ATP, Krebs 2 ATP, ETC 34 ATP (majority from ETC)

✗ Wrong: Confusing xylem and phloem transport direction

✓ Correct: Xylem: Always upward (water, minerals). Phloem: Bidirectional (glucose from source to sink)

✗ Wrong: Thinking xylem and phloem are same

✓ Correct: Xylem: Dead, thick walls, unidirectional. Phloem: Living, thin walls, bidirectional

✗ Wrong: Confusing pulmonary and systemic circulation

✓ Correct: Pulmonary: To lungs (deoxygenated). Systemic: To body (oxygenated)

✗ Wrong: Thinking blood clotting requires plasma

✓ Correct: Platelets + fibrinogen (in plasma) cause clotting. Also involves RBCs and WBCs passively

✗ Wrong: Confusing excretion and egestion

✓ Correct: Excretion: Remove metabolic wastes (urea, CO₂). Egestion: Remove undigested food (feces)

✗ Wrong: Thinking kidney filters glucose into urine

✓ Correct: Glucose filtered in Bowman's, then reabsorbed in PCT. Normal urine has NO glucose

✗ Wrong: Confusing pepsin and trypsin location

✓ Correct: Pepsin: Stomach (pH 1.5-3.5, breaks proteins to peptides). Trypsin: Small intestine (pH 7-8, breaks proteins to amino acids)

✗ Wrong: Thinking enzyme is consumed during reaction

✓ Correct: Enzymes are NOT consumed. They catalyze reaction and are released unchanged, can be used repeatedly

📝 Exam Focus

These questions are frequently asked in CBSE exams:

Photosynthesis: Light and dark reactions, location, products, factors affecting

Aerobic respiration: All stages (glycolysis, Krebs, ETC), location, ATP production

Anaerobic respiration: Difference from aerobic, products in animals vs microbes

Xylem vs Phloem: Structure, function, mechanism of transport, direction

Blood composition and circulation: RBC/WBC/Platelets functions, two circulations

Kidney: Filtration process (ultrafiltration, reabsorption, secretion), urine formation

Digestion: Enzymes and their substrates, location, pH optima

Numerical calculations on ATP production, blood pressure, kidney function

Diagram questions: Photosynthesis cycle, respiration pathway, kidney structure, heart circulation

Essay questions: Life processes overview, complete respiration pathway, excretion systems

🎯 Last-Minute Recall