Cell Biology and Homeostasis

Cellular Organelles

  • Definition: Subcellular structures within a cell, each performing specific functions.
    • Types:
    • Membrane-bound organelles (e.g., nucleus, mitochondria, Golgi complex, endoplasmic reticulum, lysosomes)
    • Non-membranous organelles

Cellular Respiration

  • Purpose: Generate energy (ATP) through the breakdown of glucose.
  • Essential for life processes and cellular metabolism.
Types of Metabolic Pathways
  1. Catabolic Pathways: Break down complex molecules, releasing energy.
    • Example: Cellular respiration.
  2. Anabolic Pathways: Synthesize complex molecules, requiring energy.
    • Example: Protein synthesis.
Phases of Cellular Respiration

  1. Glycolysis

    • Location: Cytoplasm
    • Process: Glucose is split into pyruvate, yielding a net gain of 2 ATP.
    • Oxygen Requirement: Does not require oxygen.
    • Diseases Related: Faulty glycolytic pathway noticed in diabetes and cancer.

  2. Transition Reaction

    • Process: Converts pyruvate to acetyl CoA, a high-energy fuel.
    • Oxygen Requirement: Aerobic (requires oxygen).

  3. Citric Acid (Krebs) Cycle

    • Location: Mitochondria.
    • Activities: Generates high-energy carriers (NADH, FADH2, ATP) and releases CO2 as waste.
    • Output: Produces ATP and electron carriers for the next phase.

  4. Electron Transport Chain

    • Location: Inner mitochondrial membrane.
    • Process: Electrons from NADH and FADH2 are transferred to oxygen, creating a proton gradient.
    • ATP Yield: Produces 32 ATP molecules.
Fermentation
  • Definition: Anaerobic breakdown of glucose; occurs in the cytoplasm.
  • Energy Yield: 2 ATP; much less efficient than cellular respiration.
  • Example: Lactic acid fermentation during intense exercise when oxygen is scarce.

Tissue Types and Functions

Levels of Organization
  • Cells: Basic structural unit of life.
  • Tissues: Groups of similar cells working together.
  • Organs: Composed of multiple tissue types performing specific functions.
  • Organ Systems: Groups of organs working together, such as the integumentary system.
Primary Tissue Types

  1. Epithelial Tissue

    • Function: Covers surfaces, forms glands, and lines cavities.
    • Types:
      • Simple Squamous: Thin, flat cells (diffusion).
      • Cuboidal: Cube-shaped (secretion/absorption).
      • Columnar: Taller cells (absorption).

  2. Connective Tissue

    • Function: Provides support, binds tissues, stores fat, and participates in immunity.
    • Types:
      • Loose connective (areolar, adipose)
      • Dense connective (tendons, ligaments)
      • Specialized connective (blood, bone, cartilage).

  3. Muscle Tissue

    • Types:
      • Skeletal: Voluntary, striated, attached to bones.
      • Smooth: Involuntary, non-striated, found in organs.
      • Cardiac: Involuntary, striated, heart tissue.

  4. Nervous Tissue

    • Function: Composed of neurons and supporting neuroglia.
Homeostasis
  • Definition: The maintenance of stable internal conditions in the body despite external changes.
  • Importance: Critical for survival and proper functioning of body systems.
  • Mechanisms:
    1. Negative Feedback: Opposes changes to restore balance (e.g., thermoregulation).
    2. Positive Feedback: Amplifies changes (e.g., childbirth).
Disruptions in Homeostasis
  • Can lead to disease or dysfunction in organ systems.
  • Pathophysiology: Study of alterations in normal physiological processes related to disease.

Case Study: Maya's Condition

  • Symptoms: Joint pain, stiffness, inflammation.
  • Consideration: Primary cause suspected is related to the immune system.
  • Feedback Mechanism: Positive feedback loop amplifying inflammation in her condition.