Life Processes

• Overview
  • Basic criteria for life
  • Maintenance processes (preventing damage and breakdown)
  • Need for outside sources of energy (food and oxygen)
• Nutrition
  • Autotrophic Nutrition
    • Done by green plants and some bacteria
    • Process: Photosynthesis
    • Equation: $6CO_2 + 6H_2O \xrightarrow{\text{Sunlight/Chlorophyll}} C_6H_{12}O_6 + 6O_2$
    • Events: Absorption of light, conversion to chemical energy, reduction of $CO_2$ to carbohydrates
    • Leaf Structure: Stomata (gaseous exchange & transpiration), Guard cells
  • Heterotrophic Nutrition
    • Holozoic (e.g., Amoeba, Humans)
      • Steps: Ingestion, Digestion, Absorption, Assimilation, Egestion
    • Saprophytic (e.g., Fungi)
    • Parasitic (e.g., Cuscuta, Ticks)
  • Human Digestive System
    • Alimentary canal (long tube from mouth to anus)
    • Mouth: Salivary amylase (starch digestion)
    • Stomach: Gastric glands (HCl, pepsin, mucus)
    • Small Intestine: Site of complete digestion (Liver bile + Pancreatic juice + Intestinal juice)
    • Villi: Finger-like projections for surface area and absorption
    • Large Intestine: Water absorption and waste elimination
• Respiration
  • Breakdown of glucose to release ATP (Energy Currency)
  • Pathways of Glucose Breakdown
    • Step 1: Glucose (6-carbon) $\rightarrow$ Pyruvate (3-carbon) in Cytoplasm
    • Step 2a: Absence of $O_2$ (Yeast) $\rightarrow$ Ethanol + $CO_2$ + Energy (Fermentation)
    • Step 2b: Lack of $O_2$ (Human Muscle) $\rightarrow$ Lactic Acid + Energy (causes cramps)
    • Step 2c: Presence of $O_2$ (Mitochondria) $\rightarrow$ $CO_2$ + $H_2O$ + Energy
  • Human Respiratory System
    • Pathway: Nostrils $\rightarrow$ Nasal cavity $\rightarrow$ Pharynx $\rightarrow$ Trachea (rings of cartilage) $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli (site of gas exchange)
    • Mechanism of Breathing: Action of diaphragm and rib cage (Inhalation vs Exhalation)
    • Respiratory Pigment: Hemoglobin (high affinity for oxygen)
• Transportation
  • Transportation in Humans
    • Blood
      • Plasma (fluid matrix)
      • RBCs (carry oxygen via hemoglobin)
      • WBCs (fight infections)
      • Platelets (blood clotting)
    • Heart (Four-chambered muscular pump)
      • Atria (receiving chambers) and Ventricles (pumping chambers)
      • Double Circulation (Pulmonary circulation and Systemic circulation)
      • Separation of oxygenated and deoxygenated blood
    • Blood Vessels
      • Arteries: Thick-walled, carry blood away from heart (oxygenated, except pulmonary)
      • Veins: Thin-walled with valves, bring blood to heart (deoxygenated, except pulmonary)
      • Capillaries: Thin vessels for material exchange at cellular level
    • Lymph: Tissue fluid containing WBCs, drains into lymphatic system
  • Transportation in Plants
    • Xylem: Transport of water and minerals (upward movement via transpiration pull and root pressure)
    • Phloem: Transport of food/organic solutes (sucrose) using energy (translocation)
• Excretion
  • Removal of harmful metabolic nitrogenous wastes (urea, uric acid)
  • Excretion in Human Beings
    • Urinary System: A pair of kidneys, ureters, urinary bladder, and urethra
    • Nephron (Functional unit of kidney)
      • Structure: Bowman’s capsule, glomerulus, renal tubule, collecting duct
      • Mechanism of Urine Formation:
        1. Glomerular Filtration (under high pressure in glomerulus)
        2. Tubular Reabsorption (glucose, amino acids, salts, water reabsorbed)
        3. Secretion ($K^+$, $H^+$, drugs)
    • Artificial Kidney (Dialysis): Principle of hemodialysis for kidney failure patients
  • Excretion in Plants
    • Oxygen as waste product of photosynthesis
    • Excess water removed via transpiration
    • Waste stored in old leaves (that fall off), bark, or cellular vacuoles as resins and gums