Life Processes — Class 10 Science

Life processes are the activities that maintain life in an organism. They are essential for survival, growth, and reproduction.

Main Life Processes:

• Nutrition: Process of obtaining and utilizing food for energy and growth
• Respiration: Release of energy from nutrients (food)
• Transportation: Movement of nutrients, oxygen, and wastes within organisms
• Excretion: Removal of metabolic wastes from the body
• Growth: Increase in size and complexity of organisms
• Reproduction: Production of offspring (not essential for individual survival)

Nutrition is the process of obtaining food and using it for energy and growth. Two main types exist: autotrophic (self-feeding) and heterotrophic (other-feeding).

Autotrophic Nutrition:

• Organisms manufacture their own food using inorganic substances
• Photosynthesis: Uses sunlight, CO₂, and water to make glucose
• Occurs in green plants, algae, and some bacteria

• Organisms cannot manufacture food, depend on other organisms
• Holozoic: Animals ingest solid food (digestion required)
• Saprophytic: Fungi and bacteria feed on dead matter (external digestion)
• Parasitic: Feed on living organisms (cause harm to host)

Photosynthesis is the process by which green plants manufacture glucose (food) using sunlight, carbon dioxide, and water. It occurs in two stages: light-dependent and light-independent reactions.

Overall Equation:
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
(Carbon dioxide + Water + Light → Glucose + Oxygen)

Light Reactions (In Thylakoid):

• Chlorophyll absorbs light energy
• Water molecules are split: 2H₂O → 4H⁺ + O₂ + 4e⁻
• Energy produces ATP and NADPH (electron carriers)
• Oxygen released as byproduct

• CO₂ combines with RuBP (ribulose bisphosphate)
• Forms unstable 6-carbon compound → splits to 2 molecules of PGA (3-carbon)
• PGA reduced to G3P using ATP and NADPH from light reactions
• G3P used to regenerate RuBP and form glucose

Factors affecting Photosynthesis:

Respiration is the breakdown of glucose (or other nutrients) to release energy in the form of ATP. Two types: aerobic (with oxygen) and anaerobic (without oxygen).

Aerobic Respiration Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 2880 kJ energy (38 ATP)

Anaerobic Respiration:

• In animals: Glucose → 2 Pyruvate → 2 Lactic acid (produces 2 ATP only)
• In microorganisms: Glucose → 2 Pyruvate → 2 Ethanol + CO₂ (fermentation)
• Occurs when oxygen is lacking (anaerobic bacteria, muscle cells during intense exercise)
• Much less efficient than aerobic respiration (2 ATP vs 38 ATP)

Comparison of Aerobic vs Anaerobic:

Transportation in plants involves movement of water, minerals, and food through two vascular tissues: xylem and phloem.

Xylem Transport (Ascent of Sap):

• Root Pressure: Minerals absorbed by roots create osmotic potential, water enters roots
• Capillary Action: Narrow tubes (xylem) cause water to rise against gravity
• Transpiration Pull: Water evaporates from leaves, creates tension that pulls water up
• One-way transport: Root → Stem → Leaves

• Source: Leaves manufacture glucose through photosynthesis
• Sink: Growing regions, fruits, and roots consume glucose
• Mechanism: Osmotic pressure gradient → solution flows from high to low concentration
• Bidirectional transport: Can move up or down depending on source and sink

Transportation in animals is carried out by the circulatory system, which transports oxygen, nutrients, hormones, and waste products throughout the body using blood.

Blood Composition:

• Plasma (55%): Water, proteins, glucose, ions, hormones, antibodies, urea
• RBC (Red Blood Cells): 4-6 million cells/mm³ of blood. Carry oxygen via hemoglobin
• WBC (White Blood Cells): 4,000-11,000 cells/mm³. Defend against infection
• Platelets: 1.5-4 lakh cells/mm³. Help in blood clotting

Heart Structure and Circulation:

The heart has four chambers: two atria (right and left) and two ventricles (right and left).

Pulmonary Circulation: Deoxygenated blood from body → Right atrium → Right ventricle → Pulmonary artery → Lungs (oxygenation)

Systemic Circulation: Oxygenated blood from lungs → Left atrium → Left ventricle → Aorta → Body cells (oxygen delivery)

Functions of Circulatory System:

Excretion is the removal of metabolic wastes produced during cellular respiration and other metabolic processes. Different organisms have different excretory organs and methods.

Excretion in Plants:

• Plants produce less waste because they use many byproducts (e.g., O₂ from photosynthesis)
• CO₂: Released during respiration through stomata and lenticels
• Excess water: Released through stomata (transpiration)
• Waste storage: Some wastes stored in vacuoles, bark, or fallen leaves
• Resins, tannins: Some plants produce these as waste products

Excretion in Animals:

• Kidneys: Filter blood to form urine (remove urea, excess water, ions)
• Lungs: Exhale CO₂ and excess water vapor
• Skin: Sweat glands release water, salts, and urea
• Liver: Breaks down amino acids, produces urea
• Intestines: Remove undigested food and excess bile pigments (feces)

Human Urinary System:

Filtration in Kidneys:

• Step 1 - Ultrafiltration: Small molecules (glucose, urea, water, ions) filtered from blood in Bowman's capsule
• Step 2 - Selective Reabsorption: Useful substances (glucose, amino acids, water) reabsorbed back into blood in proximal convoluted tubule
• Step 3 - Tubular Secretion: Additional wastes secreted into collecting duct
• Final Product - Urine: Contains urea, excess water, excess ions; stored in bladder; excreted through urethra

Digestion is the breakdown of complex food molecules into simpler soluble forms that can be absorbed and used by cells. Enzymes are biological catalysts that speed up digestion without being consumed.

Enzyme Definition: Enzymes are proteins that catalyze (speed up) biochemical reactions without being permanently changed.

Properties of Enzymes:

• Specific: Each enzyme catalyzes only one specific reaction
• Efficient: Speed up reactions by millions of times
• Not consumed: Enzymes can be reused multiple times
• Temperature sensitive: Optimal activity at 37°C for human enzymes
• pH sensitive: Each enzyme has optimal pH (pepsin at pH 2, trypsin at pH 8)
• Lock and Key mechanism: Substrate fits into enzyme's active site

Digestion Journey in Human Body: