1-Cells, Tissues, and Transport Mechanisms

Major and Lesser Elements in Body Mass

  • Four major elements constitute ~96% of body mass:

    • Oxygen

    • Carbon

    • Hydrogen

    • Nitrogen

  • Eight lesser elements account for ~3.6%:

    • Calcium

    • Phosphorus

    • Potassium

    • Sulphur

    • Sodium

    • Chlorine

    • Magnesium

    • Iron

  • 14 trace elements present in minimal amounts but vital for functions (e.g., iodine for thyroid hormones).

Cell Structure

  • Basic unit of life:

    • Cell membrane

    • Cytoplasm

    • DNA

  • Types of cells:

    1. Eukaryotic: Has a nucleus (e.g., plants, animals).

    2. Prokaryotic: No nucleus (e.g., bacteria).

Organelles

  • Specialized structures in cells:

    • Nucleus: Contains DNA; controls cell functions.

    • Ribosomes: Protein synthesis.

    • Endoplasmic Reticulum (ER):

    • Rough ER (rER): Has ribosomes, modifies/transports proteins.

    • Smooth ER (sER): Lacks ribosomes, synthesizes lipids.

    • Mitochondria: Powerhouses, generate ATP; contain their own DNA.

Cell Membrane

  • Physical barrier; selective permeability controls movement of substances.

  • Components:

    • Phospholipid bilayer (hydrophilic heads, hydrophobic tails).

    • Proteins (integral and peripheral).

    • Carbohydrates (glycoproteins and glycolipids for recognition).

Transport Mechanisms

  1. Passive Transport: No energy required; includes:

    • Simple diffusion: Movement of small, lipid-soluble molecules.

    • Facilitated diffusion: Requires proteins for larger/charged molecules.

    • Osmosis: Movement of water across the membrane.

  2. Active Transport: Requires ATP to move substances against concentration gradient.

Tonicity

  • Isotonic: Equal solute concentration; no net water movement.

  • Hypertonic: Higher concentration outside; water moves out (cell shrinks).

  • Hypotonic: Lower concentration outside; water moves in (cell swells).

Tissue Types

  1. Epithelial: Covers surfaces, lines cavities, forms glands.

  2. Connective: Supports, protects, and connects tissues.

  3. Muscle: Specialized for contraction/movement.

  4. Nervous: Controls body functions; transmits impulses.

Membranes Types

  1. Cutaneous: Skin; dry membrane.

  2. Mucous: Lines cavities open to the exterior; moist.

  3. Serous: Lines closed cavities; reduces friction.

  4. Synovial: Lines joints; produces lubricating fluid.