Intermediate Filaments and Proteasomes

Intermediate Filaments

• Include keratin filaments and neurofilaments for structural support.
• Composed of multiple protein types to resist internal pressure.
• Form flexible scaffolding within the cell and act as linker proteins similar to actin.

Proteasomes

• Function similarly to lysosomes as centers for protein degradation.

Microtubules

• Made of alpha (⍺) and beta (β) tubulin dimers, along with gamma (γ) tubulin for production.
• Play crucial roles in intracellular transport and movement of chromosomes, cilia, and flagella.
• Subject to antitumor drug targeting:
  • Vincristine and Colchicine: inhibit tubulin dimer polymerization, preventing microtubule formation.
  • Taxol: stabilizes microtubules, leading to cell cycle arrest during mitosis.

Molecular Motor Proteins

• Essential for movement along microtubules, facilitating intracellular transport and cellular motility.

Cell Membrane

• Composed of lipid rafts, aggregations of cholesterol and sphingomyelin associated with specific proteins.
• Functions include segregating signaling molecules and influencing membrane fluidity.

Membrane Proteins

• Integral and intrinsic membrane proteins, which are critical for cell communication and adhesion to other cells and the extracellular matrix.

Membrane Junctions

• Tight or occluding junctions: create barriers to microorganisms and minimize water loss, maintaining homeostasis.
• Gap or communicating junctions (macula communicans): connect neighboring cells via cytoplasmic tunnels (connexons), allowing diffusion of ions and small molecules.

Electrical Synapses

• A subtype of gap junctions facilitating direct electrical and chemical coupling between neurons and specific muscle cells.

Passive Transport

• Involves diffusion, where substances randomly move from areas of higher to lower concentration, driven by innate kinetic energy.

Tonicity and Osmotic Environments

• Identifies states of cells in different solutions (hypertonic, hypotonic, isotonic), emphasizing movement and behavior of cells in various osmotic conditions.

Overview of Insulin Regulation

• Increased blood glucose levels stimulate pancreatic beta cells to release insulin, lowering blood glucose through increased cellular uptake.
• Decreased glucose levels trigger a counter response, balancing the glucose levels through hormone secretion.