Cytology

Cytology Overview

• Key Cell Structures:

  • Plasma membrane, cytoplasm, nucleus.

• Plasma Membrane Functions:

  • Physical isolation between intracellular fluid (ICF) and extracellular fluid (ECF).
  • Regulates exchange with the environment, monitors environment, provides structural support.

• Plasma Membrane Composition:

  • 90-99% lipids, remainder proteins, steroids, etc.

• Phospholipid Structure:

  • Composed of hydrophilic heads and hydrophobic tails; forms a bilayer.

• Membrane Protein Roles:

  • Transporters (channels, carrier proteins), anchors, receptors, enzymes.

• Membrane Transport Types:

  • Passive Transport: No ATP required. Includes simple diffusion, facilitated diffusion, and osmosis.
  • Active Transport: Requires ATP and involves pumps, coupled transport, exocytosis, and endocytosis.

• Concentration Gradient Definition:

  • Difference in concentration of substances across the membrane.

• Osmosis:

  • Diffusion of water across a semi-permeable membrane from low to high solute concentration.

• Active Transport Mechanisms:

  • Ion pumps, coupled transporters, vesicular transport (endocytosis and exocytosis).

• Membrane Potential:

  • Voltage difference across the membrane. Maintained by the Na+/K+ pump; RMP established by K+ diffusion.
  • RMP ranges from -40 mV to -100 mV depending on cell type.

• Cytoplasm Composition:

  • Includes cytosol, cytoskeleton, and organelles (endoplasmic reticulum, ribosomes, Golgi complex, lysosomes, mitochondria, etc.).

• Cytoskeleton Types:

  • Microfilaments, intermediate filaments, microtubules (centrioles).

• Cell Division:

  • Mitosis: Division of somatic cells for growth and repair.
  • Meiosis: Reproductive division producing gametes with half chromosomal content.