Class 10 Science Notes Chapter 6 (Chapter 6) – Examplar Problems (English) Book

Detailed Notes with MCQs of Chapter 6, 'Life Processes', from your NCERT Exemplar book. This chapter is fundamental not just for your board exams but also forms a crucial base for many government exams that include General Science. Pay close attention as we break down the essential concepts.

Chapter 6: Life Processes - Detailed Notes for Competitive Exams

What are Life Processes?
The basic, essential activities performed by living organisms to maintain their life and survival on Earth are called life processes. These include:

1. Nutrition: Obtaining and utilizing energy/food.
2. Respiration: Releasing energy from food.
3. Transportation: Moving substances within the body.
4. Excretion: Removing metabolic wastes.
   (Growth, Movement, and Reproduction are also characteristics of living things, but these four are central to maintaining life).

1. Nutrition

• Definition: The process of intake of nutrients (like carbohydrates, fats, proteins, minerals, vitamins, water) by an organism, as well as the utilisation of these nutrients by the organism.

• Modes of Nutrition:

  • Autotrophic Nutrition: Organisms synthesize their own food from simple inorganic raw materials (CO₂, water). Example: Green plants, blue-green algae (Cyanobacteria).
    • Photosynthesis: The process by which green plants make their own food (glucose) using carbon dioxide and water in the presence of sunlight and chlorophyll.
      • Equation: 6CO₂ + 12H₂O ---(Sunlight + Chlorophyll)--> C₆H₁₂O₆ + 6O₂ + 6H₂O
      • Site: Chloroplasts (containing chlorophyll) in leaf cells (mainly mesophyll).
      • Raw Materials: Carbon Dioxide (taken via stomata), Water (absorbed by roots).
      • Events:
        1. Absorption of light energy by chlorophyll.
        2. Conversion of light energy to chemical energy & splitting of water molecules (photolysis) into hydrogen and oxygen.
        3. Reduction of carbon dioxide to carbohydrates (glucose).
      • Stomata: Tiny pores on the leaf surface facilitating gas exchange (CO₂ in, O₂ out) and transpiration. Guard cells regulate stomatal opening/closing.
  • Heterotrophic Nutrition: Organisms depend on other organisms for their food.
    • Holozoic: Organisms take in complex solid food. Process involves Ingestion, Digestion, Absorption, Assimilation, Egestion. Examples: Amoeba, Paramecium, Humans, Animals.
      • Amoeba: Uses pseudopodia (false feet) for ingestion (phagocytosis), forms a food vacuole where digestion occurs using enzymes, absorption into cytoplasm, assimilation for growth, and egestion of undigested food.
    • Saprophytic (Saprotrophic): Organisms feed on dead and decaying organic matter. They secrete digestive enzymes externally and absorb the digested nutrients. Examples: Fungi (yeast, mushrooms, bread mould), Bacteria.
    • Parasitic: Organisms derive nutrition from a living host, causing harm to it. Examples: Cuscuta (Amarbel), Ticks, Lice, Leeches, Tapeworms, Plasmodium (malarial parasite).

• Nutrition in Human Beings:

  • Alimentary Canal (Digestive Tract): Mouth → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus.
  • Associated Glands: Salivary glands, Gastric glands, Liver, Pancreas, Intestinal glands.
  • Process:
    1. Mouth (Buccal Cavity): Ingestion. Teeth (mastication), Tongue (mixing, tasting), Salivary Glands secrete Saliva containing Salivary Amylase (Ptyalin) which starts starch digestion (Starch → Maltose).
    2. Oesophagus: Transports food to the stomach via Peristalsis (rhythmic contraction/relaxation of muscles). No digestion occurs here.
    3. Stomach: J-shaped organ. Gastric glands secrete Gastric Juice containing:
       • HCl: Kills germs, provides acidic medium (pH 1.5-3.5) for pepsin activation.
       • Pepsin: Enzyme that digests proteins (Proteins → Peptones).
       • Mucus: Protects the inner lining of the stomach from HCl.
    4. Small Intestine: Longest part, site of complete digestion and absorption. Receives secretions from:
       • Liver: Secretes Bile Juice (stored in gall bladder). Bile emulsifies fats (breaks large fat globules into smaller ones) and makes the medium alkaline. Bile contains no enzymes.
       • Pancreas: Secretes Pancreatic Juice containing:
         • Pancreatic Amylase: Digests remaining starch → Maltose.
         • Trypsin: Digests proteins → Peptides.
         • Lipase: Digests emulsified fats → Fatty acids + Glycerol.
       • Intestinal Glands: Secrete Intestinal Juice (Succus Entericus) containing enzymes that complete digestion: Peptidases (Peptides → Amino acids), Sucrase, Lactase, Maltase (Disaccharides → Monosaccharides like glucose), Lipase (Fats → Fatty acids + Glycerol).
    5. Absorption in Small Intestine: Inner lining has numerous finger-like projections called Villi, which increase the surface area for efficient absorption. Villi are richly supplied with blood capillaries and lymph vessels (lacteals for fat absorption).
    6. Assimilation: Absorbed food is transported via blood to different cells for energy, growth, and repair.
    7. Large Intestine: Absorbs excess water and salts from undigested food. Forms faeces.
    8. Rectum: Stores faeces temporarily.
    9. Anus: Egestion (elimination of faeces).

2. Respiration

• Definition: The biochemical process of releasing energy from glucose (food) for carrying out life processes. It involves gaseous exchange (breathing) and cellular respiration.

• Breathing vs. Respiration: Breathing is the physical process of inhaling oxygen and exhaling carbon dioxide. Respiration includes breathing AND the chemical breakdown of food at the cellular level to release energy (ATP).

• Types of Respiration:

  • Aerobic Respiration: Occurs in the presence of oxygen. Complete breakdown of glucose releases a large amount of energy (approx. 38 ATP). Occurs in cytoplasm (Glycolysis) and mitochondria (Krebs cycle).
    • Glucose (6C) → Pyruvate (3C) (in Cytoplasm - Glycolysis)
    • Pyruvate (3C) ---(Presence of O₂ in Mitochondria)--> 6CO₂ + 6H₂O + Energy (ATP)
  • Anaerobic Respiration: Occurs in the absence of oxygen. Incomplete breakdown of glucose releases much less energy (2 ATP). Occurs entirely in the cytoplasm.
    • In Yeast (Fermentation):
      • Glucose → Pyruvate (in Cytoplasm)
      • Pyruvate ---(Absence of O₂ in Cytoplasm)--> Ethanol (C₂H₅OH) + 2CO₂ + Energy (ATP)
    • In Human Muscle Cells (during strenuous exercise):
      • Glucose → Pyruvate (in Cytoplasm)
      • Pyruvate ---(Lack of O₂ in Cytoplasm)--> Lactic Acid (3C) + Energy (ATP)
      • Accumulation of lactic acid causes muscle cramps.

• Respiration in Plants:

  • Gaseous exchange occurs through stomata (leaves), lenticels (stems), and general root surface.
  • Net gas exchange depends on conditions: During the day, photosynthesis is dominant (CO₂ in, O₂ out). At night, only respiration occurs (O₂ in, CO₂ out). Overall, plants release more O₂ than they consume.

• Respiration in Aquatic vs. Terrestrial Organisms:

  • Aquatic organisms (e.g., fish) use dissolved oxygen in water. Rate of breathing is faster as dissolved O₂ concentration is low. Use gills for respiration.
  • Terrestrial organisms use atmospheric oxygen. Rate of breathing is slower. Use lungs, trachea, skin etc.

• Human Respiratory System:

  • Pathway: Nostrils → Nasal Cavity (filters, warms, moistens air) → Pharynx → Larynx (voice box) → Trachea (windpipe, supported by cartilaginous rings) → Bronchi (singular: Bronchus) → Bronchioles → Alveoli (air sacs within lungs).
  • Lungs: Pair of spongy organs located in the thoracic cavity, protected by the rib cage.
  • Mechanism of Breathing:
    • Inhalation: Diaphragm contracts (flattens), Rib muscles contract (lift ribs up and outwards), Thoracic cavity volume increases, Air pressure inside decreases, Air rushes into lungs.
    • Exhalation: Diaphragm relaxes (domes upwards), Rib muscles relax (ribs move down and inwards), Thoracic cavity volume decreases, Air pressure inside increases, Air is forced out of lungs.
  • Gaseous Exchange: Occurs in Alveoli. They have thin walls, a large surface area, and are richly supplied with blood capillaries. O₂ diffuses from alveoli (high concentration) into blood; CO₂ diffuses from blood (high concentration) into alveoli.
  • Transport of Gases:
    • Oxygen: Mainly transported by Haemoglobin (respiratory pigment in Red Blood Cells - RBCs) forming oxyhaemoglobin.
    • Carbon Dioxide: Transported mainly as bicarbonate ions in plasma, also bound to haemoglobin, and dissolved in blood plasma.

3. Transportation

• Definition: The movement of substances (food, water, minerals, oxygen, hormones, waste products) from one part of the body to another.
• Transportation in Plants:
  • Xylem: Transports water and dissolved minerals upwards from roots to leaves. Composed of tracheids, vessels (dead cells), xylem parenchyma, xylem fibres. Transport is mainly due to Transpiration Pull (suction force created by evaporation of water from leaves via stomata - transpiration). Root pressure also plays a minor role.
  • Phloem: Transports food (sucrose) prepared in leaves to other parts (storage organs, growing parts). Called Translocation. Requires energy (ATP). Composed of sieve tubes, companion cells (living cells), phloem parenchyma, phloem fibres. Food can move up or down.
  • Transpiration: Loss of water in the form of water vapour from the aerial parts (mainly leaves) of the plant. Helps in absorption and upward movement of water, and temperature regulation.
• Transportation in Human Beings (Circulatory System):
  • Blood: Fluid connective tissue.
    • Plasma: Fluid matrix (mostly water). Transports CO₂, nutrients, hormones, wastes.
    • Blood Cells:
      • Red Blood Cells (RBCs/Erythrocytes): Biconcave, no nucleus (mature). Contain Haemoglobin for O₂ transport.
      • White Blood Cells (WBCs/Leukocytes): Irregular shape, nucleated. Provide immunity (fight infections). Types include neutrophils, lymphocytes, monocytes, eosinophils, basophils.
      • Platelets (Thrombocytes): Cell fragments. Help in blood clotting.
  • Heart: Muscular pumping organ. Four chambers: Right Atrium, Right Ventricle, Left Atrium, Left Ventricle.
    • Valves: Prevent backflow of blood (Tricuspid, Bicuspid/Mitral, Semilunar valves).
    • Working: Deoxygenated blood from the body enters the Right Atrium → Right Ventricle → pumped to Lungs (via Pulmonary Artery). Oxygenated blood from Lungs enters Left Atrium (via Pulmonary Vein) → Left Ventricle → pumped to the rest of the Body (via Aorta).
    • Double Circulation: Blood passes through the heart twice in one complete cycle. (Pulmonary circulation: heart-lungs-heart; Systemic circulation: heart-body-heart). Ensures complete separation of oxygenated and deoxygenated blood, allowing efficient energy supply (needed by warm-blooded animals).
  • Blood Vessels:
    • Arteries: Carry blood away from the heart. Thick, elastic walls, high pressure. Usually carry oxygenated blood (Exception: Pulmonary Artery).
    • Veins: Carry blood towards the heart. Thinner walls, valves present, low pressure. Usually carry deoxygenated blood (Exception: Pulmonary Vein).
    • Capillaries: Extremely narrow tubes connecting arteries and veins. Thin walls (one-cell thick) facilitate exchange of materials between blood and tissues.
  • Lymphatic System: Network of tissues and organs (lymph nodes, spleen, thymus, tonsils) and vessels that carry Lymph.
    • Lymph: Fluid similar to plasma but colourless and contains less protein and more lymphocytes. It leaks out from blood capillaries into tissue spaces (interstitial fluid).
    • Functions: Drains excess tissue fluid back to blood, transports digested fats (via lacteals in villi), contains lymphocytes that fight infection.

4. Excretion

• Definition: The biological process of removal of harmful metabolic wastes from the body. (Note: Egestion is removal of undigested food, not metabolic waste).
• Excretion in Plants:
  • Waste products: O₂ (byproduct of photosynthesis), CO₂ (byproduct of respiration), excess water (transpiration).
  • Other wastes stored in leaves that fall off, old xylem (as resins, gums), vacuoles, or excreted into the soil.
• Excretion in Human Beings (Urinary System):
  • Organs: Pair of Kidneys → Pair of Ureters → Urinary Bladder → Urethra.
  • Kidneys: Bean-shaped organs located in the abdomen. Basic filtration units are Nephrons.
  • Nephron Structure:
    • Bowman's Capsule: Cup-shaped structure containing a bundle of blood capillaries called the Glomerulus.
    • Renal Tubule: Long coiled tube consisting of Proximal Convoluted Tubule (PCT), Loop of Henle, Distal Convoluted Tubule (DCT).
    • Collecting Duct: Collects urine from several nephrons.
  • Mechanism of Urine Formation:
    1. Glomerular Filtration (Ultrafiltration): Blood enters the glomerulus under high pressure. Water, glucose, amino acids, salts, urea, etc., filter out from blood into Bowman's capsule. Large molecules like proteins and blood cells remain in the blood. The filtrate is called glomerular filtrate.
    2. Tubular Reabsorption (Selective Reabsorption): As the filtrate passes through the renal tubule, useful substances like glucose, amino acids, most salts, and a major amount of water are selectively reabsorbed back into the blood capillaries surrounding the tubule. Occurs mainly in PCT and Loop of Henle.
    3. Tubular Secretion: Some waste products (like urea, potassium ions, hydrogen ions, creatinine) and foreign substances (drugs) are actively secreted from the blood into the filtrate in the tubules (mainly DCT).
  • The fluid remaining after these steps is Urine. Urine contains water, urea, uric acid, salts, etc.
  • Urine flows through ureters, stored in the urinary bladder, and expelled through the urethra (Micturition).
• Artificial Kidney (Hemodialysis):
  • Used in case of kidney failure.
  • Blood from the patient's artery is passed through a dialyzer machine containing semipermeable tubes immersed in a dialyzing fluid.
  • Dialyzing fluid has the same composition as normal plasma except for nitrogenous wastes (urea).
  • Wastes from the blood diffuse into the dialyzing fluid due to concentration gradient.
  • Purified blood is returned to the patient's vein.

Key Points for Exams:

• Know the specific enzymes, their substrates, products, and location of action (e.g., Salivary amylase, Pepsin, Trypsin, Lipase).
• Understand the exact sequence of organs in the digestive and respiratory tracts.
• Differentiate clearly between aerobic and anaerobic respiration (location, products, energy yield).
• Remember the components of blood and their functions.
• Understand the concept of double circulation and its significance.
• Know the structure of the nephron and the three steps of urine formation.
• Compare transport in xylem and phloem.
• Understand the role of stomata and guard cells.
• Relate structure to function (e.g., alveoli, villi, nephron).

Multiple Choice Questions (MCQs)

1. Which of the following events in photosynthesis involves the conversion of light energy to chemical energy?
   (a) Absorption of light by chlorophyll
   (b) Reduction of carbon dioxide
   (c) Splitting of water molecules
   (d) Release of oxygen

2. In the human digestive system, bile juice is secreted by the liver. The primary role of bile is to:
   (a) Digest proteins into amino acids
   (b) Emulsify fats
   (c) Digest carbohydrates into glucose
   (d) Provide an acidic medium for pepsin

3. During anaerobic respiration in human muscle cells, glucose is broken down into:
   (a) Ethanol and Carbon dioxide
   (b) Lactic acid and Energy
   (c) Carbon dioxide, Water, and Energy
   (d) Ethanol, Carbon dioxide, and Energy

4. The tiny pores on the leaf surface responsible for gaseous exchange are called:
   (a) Lenticels
   (b) Guard cells
   (c) Stomata
   (d) Epidermis

5. Which part of the nephron is primarily responsible for selective reabsorption of useful substances like glucose and amino acids?
   (a) Glomerulus
   (b) Bowman's capsule
   (c) Loop of Henle
   (d) Proximal Convoluted Tubule (PCT)

6. Which of the following correctly represents the flow of blood in human double circulation?
   (a) Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body
   (b) Left Ventricle → Lungs → Right Atrium → Right Ventricle → Body
   (c) Right Atrium → Lungs → Left Ventricle → Left Atrium → Body
   (d) Right Ventricle → Body → Left Atrium → Left Ventricle → Lungs

7. The upward movement of water and minerals in plants through xylem is primarily driven by:
   (a) Root pressure
   (b) Translocation
   (c) Transpiration pull
   (d) Osmosis

8. Which component of blood is responsible for initiating the process of clotting?
   (a) Red Blood Cells
   (b) White Blood Cells
   (c) Plasma
   (d) Platelets

9. Organisms that derive nutrition from dead and decaying organic matter are known as:
   (a) Parasites
   (b) Holozoic organisms
   (c) Saprophytes
   (d) Autotrophs

10. In the human respiratory system, rings of cartilage are present in the:
    (a) Alveoli
    (b) Pharynx
    (c) Trachea
    (d) Bronchioles

Answer Key for MCQs:

1. (c) Splitting of water molecules (Photolysis involves light energy conversion)
2. (b) Emulsify fats
3. (b) Lactic acid and Energy
4. (c) Stomata
5. (d) Proximal Convoluted Tubule (PCT)
6. (a) Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body
7. (c) Transpiration pull
8. (d) Platelets
9. (c) Saprophytes
10. (c) Trachea

Study these notes thoroughly. Remember to correlate the processes and understand the 'why' behind each step. Good luck with your preparation!