Life Processes-1 Nutrition, Transportation, Respiration and Excretion (The Living World)

22.1 Why Do We Need Food

  • Living beings require food to survive and grow; food provides the essential raw materials and energy for life processes.
  • Functions of food:
    • Provides energy to carry out life processes such as respiration, digestion, excretion, etc.
    • Supports growth and repair of worn-out or damaged cells and tissues.
    • Enables production of enzymes and hormones in the body.
  • Energy and materials are required not only for immediate activities but also for maintenance and development over time.

22.2 NUTRITION

  • Nutrition is defined as the process by which living beings obtain food, convert it into simple absorbable forms, and use it to make substances needed by the body.
  • Types of nutrition:
    • Autotrophic nutrition (autos = self; trophos = food): green plants, algae and certain bacteria manufacture their own food via photosynthesis; they are producers in the food chain.
    • Heterotrophic nutrition (heteros = different; trophos = food): organisms that depend on others for food.
  • Heterotrophic nutrition is of several types:
    • Holozoic nutrition: ingestion, digestion and absorption of food as in Amoeba, frogs, humans.
    • Parasitic nutrition: organisms living on or inside other organisms and deriving food from them (parasites).
    • Saprotrophic nutrition: organisms (often fungi) feed on dead/decaying organic matter; they help decompose and recycle nutrients.
  • Examples and notes:
    • Cuscuta (Dodder) is a plant parasite on green plants.
    • Saprotrophs help in environmental cleaning by decomposing dead material.

22.3 NUTRITION IN PLANTS—PHOTOSYNTHESIS

  • Definition: photosynthesis is a biochemical process by which green plants manufacture their own food using CO₂ and H₂O as raw materials in the presence of sunlight and chlorophyll; O₂ is released as a by-product.
  • Overall photosynthesis equation (balanced):
    6\,CO{2} + 6\,H{2}O \rightarrow C{6}H{12}O{6} + 6\,O{2}
    (Note: the transmission sometimes shows additional water terms due to typographical issues in the source; the balanced equation above is the standard form.)
  • Photosynthesis is the only process that converts solar energy into chemical energy.
  • Essential raw materials for photosynthesis:
    • Chlorophyll: the green pigment in chloroplasts; traps light energy.
    • Light (solar energy).
    • Carbon dioxide (CO₂) and water (H₂O).
    • Occurs in chloroplasts of leaf cells.
  • Mechanism of photosynthesis occurs in two interconnected stages:
    • Light-dependent reactions (the light reactions): light is captured by chloroplasts and energy is stored in energy carriers.
    • Calvin cycle (the dark reactions; light-independent): glucose is formed in chloroplasts.
    • The two stages occur simultaneously; the light reactions require light, while the dark reactions do not, but both can operate concurrently as long as substrates and enzymes are present.
  • End products and fate:
    • Glucose is formed and may be used immediately for energy, converted, or stored as starch.
    • Oxygen is released to the atmosphere.
  • Significance of photosynthesis:
    • Provides food/energy for all living beings (basis of food chains).
    • CO₂ produced by respiration is consumed during photosynthesis, helping regulate atmospheric CO₂.
    • Oxygen released supports aerobic (oxygen-using) organisms.
  • Essential questions (INTEXT QUESTIONS 22.2):
    • Justification of the term photosynthesis (photo + synthesis).
    • Why plants appear green and what chlorophyll does for plants.
    • Glucose vs. starch: which is produced in photosynthesis and storage form.
    • Role of stomata in photosynthesis and gas exchange.

22.4 NUTRITION IN HUMANS

  • The diet should provide all essential nutrients in adequate proportions for healthy growth and development.
  • Nutrients are grouped into three broad categories:
    • Energy-yielding nutrients: carbohydrates and fats.
    • Body-building nutrients: proteins.
    • Growth-regulating nutrients: vitamins and minerals.
  • Carbohydrates:
    • Main source of energy; may be sugars, starch, or cellulose (roughage).
    • Carbohydrates types and sources:
    • Sugar: fruits, milk, sugarcane.
    • Starch: potato, wheat, rice, sweet potato.
    • Cellulose (roughage): salads and raw vegetables.
  • Fats:
    • Provide warmth and aid in transport of fat-soluble vitamins.
    • Common sources: edible oils, ghee, butter, meat, nuts (e.g., groundnuts).
    • Energy: approximately 1\ \text{g fat} \rightarrow 37\ \text{kJ} \approx 9\ \text{kcal}
  • Proteins:
    • Essential for growth and tissue formation; common sources include milk, pulses, eggs, meat.
  • Vitamins:
    • Vital for normal growth and body maintenance; required in small amounts.
    • Vitamins can be water-soluble (e.g., B-complex, C) or fat-soluble (A, D, E, K).
    • Vitamin table highlights sources, functions and deficiency diseases (e.g., Vitamin A for vision; Vitamin C for healthy gums; deficiencies lead to night blindness, scurvy, etc.).
  • Minerals:
    • Required in small quantities; key examples include iron, calcium, potassium, iodine.
    • Functions: iron forms haemoglobin; calcium strengthens bones/teeth; iodine supports thyroid function.
  • Water:
    • Makes up about 65-70% of body weight; regulates body temperature and acts as a medium for biochemical reactions.
  • Raw vegetables and roughage:
    • Important for bowel movements and preventing constipation.
  • 22.4.1 Balanced diet:
    • A balanced diet contains adequate amounts of carbohydrates, fats, proteins, vitamins, minerals, and water in proper proportions.
    • Proportions vary with age, sex, and pregnancy.
  • Activity 22.1: Self-assessment of seven-day diet for balance.

22.5 DIGESTION – THE PROCESS OF NUTRITION IN HUMAN BEINGS

  • Digestion definition: conversion of complex food into simpler substances that can be absorbed by cells; ingestion is taking in food.
  • Digestive system (alimentary canal) and associated glands:
    • Alimentary canal: mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum.
    • Glands: salivary glands, liver, pancreas; they secrete digestive juices.
  • Enzymes:
    • Digestive enzymes are proteins that speed up chemical reactions; largely unchanged during reactions and can be reused.
  • Steps of nutrition (overview of the process): ingestion, digestion, absorption, assimilation, egestion.
  • Mouth:
    • Carbohydrates (starch) are broken down by salivary amylase into sugars; saliva lubricates food.
  • Oesophagus:
    • No digestion here; peristaltic contractions push food toward the stomach.
  • Stomach:
    • Gastric juice contains hydrochloric acid (HCl) and pepsinogen; HCl activates pepsinogen to pepsin and kills bacteria.
    • Proteins are broken into peptones by pepsin.
  • Small intestine:
    • Duodenum is the first part; emulsification of fats occurs via bile from the liver (stored in the gall bladder) to create an alkaline medium for pancreatic enzymes.
    • Pancreatic juice contains:
    • Trypsin: proteins to smaller peptides
    • Amylase: starch to maltose
    • Lipase: fats to fatty acids and glycerol
    • Digestion completes in small intestine; villi increase surface area for absorption; capillaries absorb digested nutrients into the blood; undigested material moves to the large intestine.
  • Large intestine:
    • Water absorption and formation of feces; rectum stores and expels feces via the anus.
  • Absorption, assimilation, and egestion defined:
    • Absorption: uptake of digested food by blood capillaries in the villi.
    • Assimilation: use of absorbed nutrients by cells to release energy and build cellular components.
    • Egestion: elimination of undigested material.
  • Jaundice note: bilirubin buildup causes yellowing of skin; linked to liver infection; hepatitis virus is a common cause.
  • INTEXT QUESTIONS 22.4 (short answers): enzymes (pepsin) and movement (peristalsis), pancreas/liver secretions, enzymes in pancreatic juice, acid involved in digestion (HCl).

22.6 DEFICIENCY DISEASES OR NUTRITIONAL DISORDERS

  • Malnutrition refers to improper or inadequate diet; deficiency diseases arise from lack of essential nutrients.
  • Types of deficiency disorders:
    • Protein Energy Malnutrition (PEM): deficiency of proteins in the diet leading to conditions like Marasmus and Kwashiorkor.
    • Mineral deficiency diseases: goitre (iodine deficiency) and anaemia (iron deficiency).
    • Vitamin deficiency diseases: xerophthalmia, night blindness, beri-beri, pellagra, scurvy, rickets, etc. (Table 22.1 summarizes vitamins, sources, functions, and deficiency diseases – see original tables for details).
  • PEM details:
    • Marasmus: in infants; symptoms include wasting of muscles, loose skin folds, prominent ribs, slowed growth; managed by milk feeding and protein-rich diet.
    • Kwashiorkor: in 1–5-year-olds; symptoms include enlarged liver due to edema, skin darkening with a scaly appearance, reddish-brown hair, thin legs, growth retardation; treat with protein-rich diet.
  • Mineral deficiency specifics:
    • Goitre: iodine deficiency causes thyroid enlargement; iodized salt and seafood are good iodine sources.
    • Anaemia: iron deficiency reduces haemoglobin; iron-rich foods help.
  • Vitamin deficiency notes: refer to Table 22.1 for specifics.
  • Food adulteration:
    • Adulterants degrade quality and safety of foods; common adulterants vary by item (see Table 22.3 in the source).
  • INTEXT QUESTIONS 22.5: PEM full form and diseases; vitamin deficiency diseases; reason for iodised salt advertisements.

22.7 TRANSPORTATION

  • Transportation refers to the distribution of food, oxygen, and wastes within organisms; a circulatory system moves fluids (blood or lymph) for transport.
  • Key concepts:
    • Circulation ensures delivery to tissues and removal of wastes;
    • Hormones and other substances are transported to target organs as needed.

22.7.1 Transport of Materials in Plants

  • Water transport (xylem):
    • Roots uptake water and minerals; water moves upward to leaves via xylem (tracheids and vessels).
    • Upward movement (ascent of sap) against gravity is driven by transpiration pull: evaporation of water from stomata creates a vacuum that pulls water up the plant.
  • Food transport (phloem):
    • Sugars and other nutrients synthesized in leaves are transported to other parts of the plant via phloem (sieve tubes).
    • Translocation refers to this movement; food may be stored in fruits, stems, or roots.
  • Visuals: root hairs, sieve tubes, and the movement mechanisms.

22.8 TRANSPORTATION IN HUMAN BEINGS

  • Human circulatory system components:
    • Heart: muscular pump; four chambers (two atria, two ventricles).
    • Blood vessels: arteries (carry blood away from heart), veins (carry blood toward the heart), capillaries (sites of exchange between blood and tissues).
    • Circulating fluids: blood, tissue fluid, lymph.
  • Blood composition and cells:
    • Red blood cells (RBCs, erythrocytes): contain haemoglobin; no nucleus; transport oxygen and carbon dioxide.
    • White blood cells (WBCs, leucocytes): defend against infections; some engulf pathogens or produce antibodies.
    • Platelets (thrombocytes): small fragments; essential for blood clotting.
  • Functions of blood: transport nutrients, oxygen, carbon dioxide, hormones, waste; distribution of medicines; maintains homeostasis.
  • Blood groups and transfusion:
    • ABO system: four blood groups A, B, AB, O with associated antigens on RBCs and antibodies in plasma.
    • Compatibility: donors must match recipients to avoid agglutination; universal donor is O negative (O) and universal recipient is AB.
  • Lymphatic system:
    • Lymph is a circulating fluid that returns proteins and fluids to tissues; lymphocytes fight infections.
  • Circulatory system disorders:
    • Heart attack, anemia, leukemia, hypertension; severity and symptoms related to blood flow and oxygen delivery.
  • INTEXT QUESTIONS 22.6: roles of blood vessels, why heart beats continuously, etc.

22.8.4 Lymphatic system (summary)

  • Lymph flows in one direction toward the heart; lymphocytes fight infections; it helps return proteins and fluids to the circulation.

22.9 RESPIRATION

  • Breathing vs respiration:
    • Breathing (or ventilation) is the physical process of inhaling O₂ and exhaling CO₂ via diffusion in the lungs.
    • Respiration is the cellular process of oxidizing glucose to release energy (ATP) and produce CO₂ and H₂O; it includes gaseous exchange and energy release.
  • Respiration in plants:
    • Plants respire via root hairs for O₂ uptake from soil; leaves exchange gases through stomata; lenticels in older bark allow gas exchange.
  • 22.9.3 Human respiratory system:
    • External nares, nasal cavities, internal nostrils, pharynx, larynx, trachea, bronchi, bronchioles, alveoli (air sacs) where gas exchange occurs.
    • Voice box (larynx) sits on the trachea; trachea has cartilage rings to prevent collapse.
  • 22.9.4 Mechanism of breathing (ventilation):
    • Inhalation: diaphragm contracts (flattens) and rib cage expands; thoracic volume increases; pressure decreases; air enters alveoli.
    • Exhalation: diaphragm relaxes (dome-shaped), rib cage lowers; thoracic volume decreases; pressure increases; CO₂-rich air is expelled.
  • 22.9.5 Breathing rate:
    • At rest, about 16–18 breaths per minute; rate increases with exercise, fever, pain, or stress.
  • 22.9.6 Gas exchange between blood and tissues:
    • Oxygen from alveoli diffuses into blood; CO₂ from tissues diffuses into blood to be carried back to the lungs.
  • 22.9.7 Cellular respiration:
    • Occurs in mitochondria; oxygen is used to oxidize glucose to release energy (ATP) and CO₂ and H₂O as by-products.
  • Practical notes:
    • High altitude adaptation includes increased RBC count and larger thoracic capacity; divers use oxygen supplies due to reliance on atmospheric oxygen.
    • Artificial respiration (mouth-to-mouth) and ventilators support respiration during asphyxia or respiratory failure.

22.10 HUMAN EXCRETORY SYSTEM

  • Excretion is the removal of metabolic wastes from the body; the urinary/excretory system removes nitrogenous wastes and helps maintain homeostasis.
  • Major organs: kidneys (two), ureters (tubes from each kidney), urinary bladder, urethra.
  • Nephron: structural and functional unit of the kidney; components include Bowman’s capsule, glomerulus, proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), with surrounding capillaries.
  • Filtration and reabsorption:
    • Blood entering the glomerulus is filtered in Bowman’s capsule to form nephric filtrate. Red blood cells and proteins remain in the blood.
    • Useful substances are reabsorbed from the renal tubules back into surrounding capillaries; excess water and salts are reabsorbed as needed.
    • Waste products (urea and others) remain in the filtrate and become urine, which passes to the ureters, bladder, and urethra.
  • Kidney functions beyond excretion:
    • Osmoregulation: regulates body water content.
    • Mineral balance: maintains proper mineral ion concentrations in blood.
  • Other excretory roles:
    • Lungs remove CO₂; skin excretes salts via sweat; liver processes various waste products.
  • Maintenance of internal environment (osmoregulation): balance of water and minerals is crucial for health.
  • Kidney failure and treatments:
    • Dialysis and kidney transplant as life-saving options; artificial kidney (dialyzer) used in dialysis to remove wastes from the blood when kidneys fail.
  • INTEXT QUESTIONS 22.9:
    • Identify urine storage organ, nephron filtration location, and reabsorption of useful substances.

What you have learned (summary pointers)

  • Nutrition involves converting food into energy and building blocks; photosynthesis is the primary source of organic matter and atmospheric oxygen.
  • A balanced diet delivers carbohydrates, fats, proteins, vitamins, minerals, and water in appropriate amounts; malnutrition leads to PEM, mineral, or vitamin deficiencies.
  • Digestion transforms complex foods into absorbable nutrients; enzymes play key roles in breaking down carbohydrates, proteins, and fats; the small intestine is the major site of absorption.
  • The circulatory system distributes nutrients and oxygen, removes wastes, and supports immune and endocrine functions; blood groups determine compatibility for transfusions.
  • The respiratory system enables gas exchange; breathing and cellular respiration work together to supply energy to cells; diffusion drives gas exchange in alveoli.
  • The excretory system removes metabolic wastes and maintains internal balance; kidneys (nephrons) perform filtration and reabsorption to form urine; dialysis and transplants are options for kidney failure.
  • Overall, life processes are interconnected: nutrition provides energy and materials, transport distributes them, respiration provides usable energy, and excretion maintains internal balance for health and function.

Key Formulas and Numerical References

  • Photosynthesis (balanced):
    6\,CO{2} + 6\,H{2}O \rightarrow C{6}H{12}O{6} + 6\,O{2}
  • Fat energy yield (typical):
    1\ \text{g fat} \rightarrow 37\ \text{kJ} \approx 9\ \text{kcal}
  • Water composition in body: approximately 65\%\text{-}70\% of body weight is water.
  • Normal human blood pressure (example): 120/80\ \text{mmHg}
  • Normal resting breathing rate (example): \approx 16\text{–}18\ \text{breaths per minute}
  • Heart rate example: ~72 beats per minute (normal resting heart rate)
  • Common deficiency diseases (examples): PEM (Marasmus, Kwashiorkor); Goitre (iodine); Anaemia (iron); Night blindness (Vitamin A); Scurvy (Vitamin C); Rickets (Vitamin D); Pellagra (Vitamin B3)

Connections and Practical Implications

  • Nutrition, especially balanced diet, is foundational for growth, cognitive development, and disease prevention; malnutrition has wide-reaching health and social consequences.
  • Understanding digestion highlights the importance of a fiber-rich diet and the role of enzymes in food processing.
  • The transport system underpins physiological regulation, immune function, and endocrine signaling; blood groups matter in medical procedures.
  • Respiratory health is central to energy production; adequate exchange of gases is essential for cellular respiration and ATP production.
  • Excretory system maintains internal homeostasis; kidney health is critical for filtering wastes and maintaining ion and fluid balance; dialysis and transplantation are important medical interventions.