Life Processes

Class X · CBSE Biology · Chapter 6

🌿 Nutrition
Autotrophic Heterotrophic Chlorophyll 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ Holozoic · Saprophytic · Parasitic

☀️ Photosynthesis — Live Process

CO₂
CO₂
CO₂
O₂
O₂
O₂
← CO₂ + H₂O (Reactants) ☀️ Sunlight + Chlorophyll O₂ + Glucose → (Products)
6CO₂ + 6H₂O — sunlight / chlorophyll → C₆H₁₂O₆ + 6O₂
Light reactions (thylakoid) produce ATP + NADPH · Dark reactions (stroma/Calvin cycle) fix CO₂ → glucose
🔬 Chlorophyll absorbs red and blue light, reflects green — that's why leaves appear green. Only the green parts of a leaf can photosynthesize.
AUTOTROPHIC

Photosynthesis Stages

  • Light Reaction (thylakoid): Splits H₂O, releases O₂, forms ATP + NADPH
  • Dark Reaction (stroma): CO₂ + ATP + NADPH → Glucose (Calvin cycle)
  • Requires chlorophyll, sunlight, CO₂, H₂O
  • Stomata open to take in CO₂
HETEROTROPHIC

Holozoic Nutrition

  • Ingest → Digest → Absorb → Assimilate → Egestion
  • Herbivores: Plants only (cow, deer)
  • Carnivores: Animals only (lion, eagle)
  • Omnivores: Both (humans, bears, cockroach)
  • Amoeba: Engulfs food via pseudopodia (phagocytosis)
HETEROTROPHIC

Saprophytic & Parasitic

  • Saprophytic: Dead/decaying matter (fungi, bacteria)
  • Important for decomposition & nutrient cycling
  • Parasitic: Live on/in a living host
  • Ectoparasites: Lice, leeches (on surface)
  • Endoparasites: Tapeworm, Ascaris (inside host)
  • Cuscuta: Plant parasite (dodder)
NUTRITION IN AMOEBA

Amoeba — Holozoic

  • Pseudopodia engulf food particle
  • Food vacuole formed inside cytoplasm
  • Lysosomes release enzymes → digestion
  • Nutrients diffuse into cytoplasm
  • Undigested remnants expelled by exocytosis

🍽️ Human Digestive Journey — Click each step

👄

Mouth (Buccal Cavity)

Teeth mechanically break food. Salivary amylase (ptyalin) begins starch digestion → maltose. Saliva lubricates food into a bolus. pH ≈ 7.

🌀

Oesophagus

Muscular tube connecting mouth to stomach. Peristalsis (wave-like muscular contractions) pushes the bolus downward. No digestion occurs here.

🫃

Stomach

Gastric glands secrete HCl (pH ≈ 2) — kills bacteria. Pepsin (activated by HCl) digests proteins → peptides. Mucus protects stomach lining. Food becomes chyme.

🔄

Small Intestine

Liver secretes bile — emulsifies fats. Pancreatic juice: Trypsin (proteins), Lipase (fats), Amylase (starch). Intestinal enzymes: Maltase, Sucrase. Villi & microvilli absorb nutrients into the blood & lymph.

💧

Large Intestine (Colon)

Absorbs remaining water and electrolytes. Gut bacteria produce vitamins (B12, K). Undigested material forms faeces, stored in rectum, then egested via the anus.

💨 Respiration
ATP — energy currency Mitochondria Cytoplasm (Glycolysis) Aerobic vs Anaerobic Alveoli

🫁 Breathing — Gas Exchange in Alveoli

Left Lung Right Lung

🫁 Inhaling O₂ ...

🔬 ~300 million alveoli in each lung give a total surface area of ~70 m². Walls are 1 cell thick with a dense capillary network. O₂ diffuses from air → blood; CO₂ from blood → air (passive diffusion along concentration gradients).

⚡ Choose Respiration Type

38
ATP molecules
Complete oxidation
Maximum efficiency
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP
Occurs in mitochondria · Requires O₂ · Complete oxidation of glucose
🔬 3 stages: Glycolysis (cytoplasm, 2 ATP) → Krebs cycle (mitochondrial matrix, 2 ATP) → Electron Transport Chain (inner mitochondrial membrane, 34 ATP). O₂ is the final electron acceptor.
2
ATP molecules
Partial oxidation
Very low efficiency
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP
Yeast fermentation · Used in bread, wine and beer production
🔬 CO₂ produced causes bread dough to rise. Ethanol (alcohol) is a by-product used in brewing. Industrial application: biofuel production from fermentation.
STAGE 1

Glycolysis

  • Occurs in cytoplasm
  • Glucose (6C) → 2 Pyruvate (3C)
  • Net yield: 2 ATP + 2 NADH
  • Does NOT require O₂
  • Common step for both aerobic & anaerobic
STAGE 2

Krebs Cycle

  • Occurs in mitochondrial matrix
  • Pyruvate → Acetyl CoA → CO₂ released
  • Produces NADH and FADH₂
  • Yield: 2 ATP per glucose molecule
  • Aerobic only — requires O₂
STAGE 3

Electron Transport Chain

  • Inner mitochondrial membrane
  • NADH + FADH₂ donate electrons → ATP formed
  • Produces 34 ATP (bulk of energy)
  • O₂ is the final electron acceptor → H₂O
  • Chemiosmosis drives ATP synthesis
BREATHING

Human Respiratory Tract

  • Nose: Filters, warms, moistens air; mucus traps dust
  • Trachea: Lined with cilia and mucus
  • Bronchi → Bronchioles → Alveoli
  • Diaphragm + intercostal muscles drive breathing
  • Haemoglobin in RBC transports O₂ (oxyhaemoglobin)
❤️ Transportation
Xylem — Water & Minerals Phloem — Food (Sucrose) Double Circulation Haemoglobin Transpiration Pull

❤️ Human Heart — Double Circulation

The heart beats ~70 times/min, pumping blood through two separate circuits simultaneously.

Right Atrium Receives deoxygenated blood from body via vena cava
Left Atrium Receives oxygenated blood from lungs via pulmonary vein
Right Ventricle Pumps deoxygenated blood to lungs via pulmonary artery
Left Ventricle Pumps oxygenated blood to body via aorta. Thickest walls.
🔬 Double circulation means blood passes through the heart TWICE per complete circuit — pulmonary (heart → lungs → heart) and systemic (heart → body → heart). This maintains high pressure for efficient oxygen delivery to all tissues.

🩸 Blood Composition

Plasma 55%
RBC 40%
WBC
Plasma (55%) — Water, proteins, glucose, hormones, CO₂, ions
RBC (40%) — Haemoglobin, O₂ transport; no nucleus in mature human RBCs
WBC (~1%) — Immune defence; phagocytosis & antibody production
Platelets (~4%) — Blood clotting; thrombocytes; no nucleus
PLANTS — XYLEM

Xylem Transport

  • Carries water + dissolved minerals upward
  • Unidirectional: roots → stem → leaves
  • Driving force: Transpiration pull (cohesion-tension theory)
  • Root pressure also contributes (push from below)
  • Dead cells, hollow, no cytoplasm
  • Water enters root hair cells by osmosis
PLANTS — PHLOEM

Phloem Transport

  • Transports food (sucrose, amino acids)
  • Bidirectional: leaves → roots AND fruits/seeds
  • Process called Translocation
  • Requires ATP (energy-dependent active transport)
  • Living cells: sieve tubes + companion cells
  • Source (leaf) → Sink (roots, growing tips, fruits)
BLOOD VESSELS

Arteries vs Veins

  • Arteries: Carry blood AWAY from heart
  • Thick muscular elastic walls; high pressure; no valves
  • Pulmonary artery carries deoxygenated blood
  • Veins: Carry blood TOWARD heart
  • Thin walls, lower pressure; have valves
  • Capillaries: Site of O₂/CO₂/nutrient exchange; 1 cell thick
LYMPH

Lymphatic System

  • Lymph: Pale yellowish fluid leaked from capillaries
  • Returns excess interstitial fluid back to blood
  • Carries digested fats absorbed from small intestine
  • Contains WBCs — important for immunity
  • Lymph nodes filter pathogens before returning to blood
🫘 Excretion
Urea — nitrogenous waste Nephron — functional unit Ultrafiltration Selective Reabsorption Dialysis

🔬 Urine Formation in Nephron — 3 Steps

Step 1: Ultrafiltration
Blood enters the glomerulus (a tuft of capillaries) at HIGH pressure. Small molecules are forced out through capillary walls into the Bowman's capsule, forming the glomerular filtrate.
Filtered out (into tubule): Water, glucose, amino acids, urea, salts, uric acid, creatinine
Retained in blood: RBC, WBC, platelets, large plasma proteins
🔬 ~180 litres of filtrate formed per day in both kidneys, but only 1.5–1.8 litres become urine after reabsorption — over 99% is reclaimed!

🏥 Artificial Kidney — Haemodialysis

← Blood enters (with urea/waste) Semi-permeable membrane Waste diffuses out ↓
🔬 Dialysing fluid is isotonic (same concentration as normal blood plasma) so only waste molecules (urea, excess salts) diffuse out by osmosis/diffusion. Blood cells and large proteins cannot pass through the cellophane membrane.
HUMAN EXCRETION

Organs of Excretion

  • Kidneys: Urea, uric acid, excess salts (via urine)
  • Skin: Sweat — water, NaCl, traces of urea
  • Lungs: CO₂ + water vapour (exhaled)
  • Liver: Bile pigments (bilirubin from broken RBCs)
  • Liver converts amino acids → urea (urea cycle)
NEPHRON

Parts of the Nephron

  • Glomerulus: Ultrafiltration (high pressure)
  • Bowman's capsule: Collects glomerular filtrate
  • Proximal tubule: Reabsorbs glucose, amino acids, Na⁺, water
  • Loop of Henle: Concentrates urine; water recovery
  • Distal tubule + Collecting duct: Final adjustment; regulated by ADH
PLANTS

Excretion in Plants

  • O₂ (photosynthesis) expelled via stomata
  • CO₂ (respiration) released via stomata
  • Excess water removed by transpiration
  • Wastes stored: vacuoles, bark, resins, gums, tannins
  • Leaf fall removes accumulated waste products
  • NO specialised excretory organ needed
URINE

Composition of Urine

  • Water: ~95%
  • Urea: ~2% (main nitrogenous waste)
  • Uric acid, creatinine, inorganic salts: ~3%
  • Normal pH: 4.5 – 8.0 (average ~6)
  • Yellow colour: Urochrome (urobilin pigment)
  • Absence of glucose & protein (presence = disease signal)