Science Class 10 Notes: Life Processes by Prashant Kirad

Life Processes Overview

• Definition: Life processes are a set of interconnected activities within an organism that collectively contribute to its repair and maintenance. These processes are essential for sustaining vitality.

• Key Processes (RENT Acronym):

  • Respiration (R): Acquiring oxygen from outside the body and using it to break down food for cellular needs.

  • Excretion (E): The process of removing and expelling metabolic waste by-products from the internal environment to the outside of the organism.

  • Nutrition (N): The transformative process of acquiring external energy sources (food) and transferring them internally for sustenance.

  • Transportation (T): An internal mechanism responsible for conveying nutrients, gases, and oxygen from one location to another within the body.

Modes of Nutrition

• Autotrophic Nutrition:

  • Mechanism: Organisms derive nutrition from basic inorganic sources like carbon dioxide ($CO_2$) and water ($H_2O$).

  • Examples: Green plants and certain bacteria.

  • Photosynthesis: The fundamental process where autotrophs absorb external substances and convert them into stored energy.

  • Storage: Surplus carbohydrates are stored in plants as starch. In the human body, energy is stored in the form of glycogen.

• Heterotrophic Nutrition:

  • Mechanism: Organisms rely on complex substances that must be broken down into simpler forms for maintenance and growth.

  • Bio-catalysts: Enzymes are used to facilitate these chemical breakdowns.

  • Examples: Animals and fungi.

Photosynthesis and Stomatal Function

• Events During Photosynthesis:

  1. Chlorophyll absorbs light energy.

  2. Transformation of light energy into chemical energy.

  3. Separation of water ($H_2O$) molecules into hydrogen and oxygen.

  4. Conversion of carbon dioxide ($CO_2$) into carbohydrates through the process of reduction.

• Iodine Test: A blue-black coloration in leaf regions indicates the presence of starch resulting from photosynthesis.

• Stomata (Pores on Leaves):

  • Function: Facilitate massive gaseous exchange for photosynthesis and respiration.

  • Location: Predominantly found on the underside of leaves.

  • Regulation: The opening and closing are controlled by Guard Cells.

  • Mechanism: Guard cells swell with water influx to open the pore and shrink to close the pore. Stomata close to prevent excessive water loss when $CO_2$ is not required.

• Gas Exchange Sites: Beyond leaves, gas exchange also occurs across the surfaces of stems and roots.

Heterotrophic Nutrition Categories

• Saprophytic Nutrition:

  • Organisms feed on dead and decomposed organic matter.

  • Digestion occurs partially outside the body before absorption.

  • Example: Fungi.

• Parasitic Nutrition:

  • Organisms feed at the expense of a host, causing it harm.

  • Ectoparasites: Live on the host (e.g., leeches).

  • Endoparasites: Live inside the host (e.g., $Ascaris$).

  • Parasitic Plants: $Cuscuta$.

• Holozoic Nutrition:

  • Digestion happens inside the organism's body after ingestion.

  • Example: Most animals.

Nutrition in Unicellular Organisms

• Amoeba:

  • Uses temporary finger-like extensions of the cell surface to engulf food.

  • These extensions merge to form a food-vacuole.

  • Complex substances are broken down within the vacuole and diffuse into the cytoplasm.

  • Undigested material is expelled at the cell surface.

• Paramoecium:

  • A unicellular organism with a distinct shape.

  • Ingests food at a specific designated location.

  • The cell surface is covered with cilia, which move food toward the intake spot.

Human Digestive System

• Alimentary Canal: A long tube extending from the mouth to the anus.

• Mouth and Salivary Glands:

  • Saliva contains salivary amylase, which breaks down complex starch into simple sugars.

  • Peristalsis: Rhythmic contractions of muscles lining the canal push food forward.

• The Stomach:

  • Gastric Glands: Located in the stomach wall, they secrete:

    1. Hydrochloric Acid ($HCl$): Creates an acidic environment and activates pepsin.

    2. Pepsin: A protein-digesting enzyme.

    3. Mucus: Shields the inner lining from the corrosive effects of the acid.

  • Sphincter Muscle: Regulates the release of food in small amounts into the small intestine.

• The Small Intestine:

  • Length: Herbivores (grass eaters) have a longer intestine for cellulose digestion; Carnivores (meat eaters) have a shorter one.

  • Function: Site for complete digestion of carbohydrates, proteins, and fats.

  • Liver Secretion: Bile juice alkalizes food and bile salts emulsify (break down) large fat globules.

  • Pancreatic Juice: Contains trypsin (protein digestion) and lipase (breaking down emulsified fats).

  • Intestinal Juice: Final conversion of proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol.

  • Villi: Finger-like projections that increase surface area for absorption; richly supplied with blood vessels to distribute nutrients.

• The Large Intestine: Absorbs water from unabsorbed food before expulsion.

Respiration and Energy Currency

• Definition: Respiration is an oxidation reaction where carbohydrates are oxidized to produce energy.

• Site: Mitochondria.

• $ATP$ (Adenosine Tri-Phosphate): The energy currency of the cell. Energy is stored in high-energy phosphate bonds and released as needed for metabolic reactions.

• Steps of Respiration:

  • Glucoses (a $6$ carbon molecule) is broken down into Pyruvate (a $3$ carbon molecule) in the cytoplasm.

• Aerobic Respiration: Occurs in the presence of oxygen. Pyruvic acid converts into $CO_2$, energy, and water within the mitochondria.

• Anaerobic Respiration:

  • In Microbes (Yeast): Pyruvic acid converts to ethyl alcohol and $CO_2$.

  • In Muscle Cells: Occurs during intense exercise. Pyruvic acid converts to lactic acid, resulting into a throbbing pain or cramps. Resting alleviates this by reducing lactic acid deposition.

The Human Respiratory System

• Components: Nose, nasal cavities, pharynx, larynx, trachea (windpipe), bronchi, bronchioles, and alveoli.

• Lungs: Enclose the bronchioles and alveoli.

• Mechanics of Breathing:

  • Inhalation: Rib cage muscles and diaphragm contract, expanding the thoracic cavity. Pressure decreases, and air rich in oxygen rushes into the lungs.

  • Exhalation: Expelling air rich in carbon dioxide.

• Alveoli: Provide a massive surface area for gas exchange between the air and surrounding blood vessels.

Transportation in Humans and Plants

• The Circulatory System (Humans):

  • Heart: A muscular organ made of cardiac muscles; consists of four chambers (Right Atrium, Right Ventricle, Left Atrium, Left Ventricle).

  • Blood Vessels:

    • Arteries: Thick-walled; carry oxygenated blood to organs (Exception: Pulmonary arteries carry deoxygenated blood).

    • Veins: Thin-walled; carry deoxygenated blood to the heart (Exception: Pulmonary veins carry oxygenated blood). Contain valves to prevent backflow.

    • Capillaries: Single-cell thick walls for exchange.

  • Blood Components:

    1. Plasma: Watery matrix.

    2. RBCs: Contain hemoglobin (red pigment) for oxygen and carbon dioxide transport.

    3. WBCs: Part of the immune system.

    4. Platelets: Responsible for blood coagulation to prevent loss.

  • Lymph: A yellowish fluid lacking RBCs and having fewer proteins; flows from tissues toward the heart and helps in the immune response.

  • Double Circulation: Blood passes through the heart twice; deoxygenated blood through the right side and oxygenated blood through the left side.

• Plant Transportation:

  • Xylem: Transports water/minerals from roots to leaves. Uses suction from transpiration and ion concentration gradients. No energy ($ATP$) is consumed.

  • Phloem: Transports products of photosynthesis (translocation). Uses energy from $ATP$ to transfer substances like sucrose.

  • Transpiration: Loss of water vapor from aerial parts; aids in cooling and the upward transport of minerals.

Excretion Systems

• Human Excretory System:

  • Components: Pair of kidneys, pair of ureters, urinary bladder, and urethra.

  • Kidney: Bean-shaped; located near the vertebral column. Contains millions of filtration units called nephrons.

  • Nephron Structure:

    • Malpighian Body: Bowman’s capsule (cup-like) and Glomerulus (capillary cluster).

    • Renal Tubule: Proximal Convoluted Tubule (PCT), Loop of Henle, and Distal Convoluted Tubule (DCT).

  • Urine Formation: Blood is filtered in the glomerulus into Bowman’s space. Useful substances (glucose, salts, water) are reabsorbed in the tubules before the remaining waste becomes urine.

• Haemodialysis: An artificial kidney (dialyzer) process that filters waste, electrolytes, and excess water from blood via a semipermeable membrane when kidneys fail.

• Plant Excretion:

  • Gaseous Waste: $O_2$ (from photosynthesis) and $CO_2$ (from respiration) expelled via stomata.

  • Water Waste: Expelled via transpiration.

  • Organic By-products: Stored as gums, oils (orange, jasmine, eucalyptus), resins, or latex (rubber, papaya) in bark, stems, and leaves until they are shed.

Questions & Discussion

• Muscle Cramps: Caused by anaerobic respiration in muscle cells during vigorous exercise, producing lactic acid and $ATP$.

• Heart Structure: Four chambers; atria receive blood, ventricles pump blood. Valves between them prevent backflow.

• Photosynthesis in Desert Plants: Stomata open at night to take in $CO_2$ and form an intermediate; this is acted upon by energy absorbed by chlorophyll during the day to prevent water loss.

• Diffusion in Tissues: Exchange of gases between blood and tissues occurs via diffusion. Hemoglobin has a high affinity for $O_2$, carrying it from lungs to tissues.

• Organs of Excretion: Kidneys (urea), Lungs ($CO_2$), Skin (sweat/oil), Large Intestine (undigested food), Liver (bile pigments/ammonia to urea).

• Coating Leaves with Vaseline: The plant will die because blocking stomata stops gas exchange (respiration/photosynthesis) and transpiration (stopping the ascent of sap/water absorption).