BSCI 330 - nov 21 (pt 1)

Snares and Vesicle Dynamics: Discussed the role of SNARE proteins in vesicular transport; different compartments (ER, Golgi, Cell Surface) work together.

Definition: A transient compartment formed during endocytosis; contains early, late, and recycling endosomes.
Endocytosis: Material can enter from both the plasma membrane and Golgi; early endosomes mature into late endosomes, which gradually become more acidic.

Early Endosomes: Arise from internalization of material, transition into late endosomes.
Late Endosomes: Further process material and may then fuse with lysosomes for degradation.
Recycling Endosomes: Responsible for returning membrane proteins and receptors to the cell surface post-endocytosis.

Recycling and Degradation: Different receptors have different fates—nutrient receptors typically recycle while signaling receptors may be degraded to regulate signaling.
Types of Endocytosis:
- Phagocytosis: Engulfing large particles (over 250 nm); used primarily by immune cells.
- Pinocytosis: Ingestion of fluids and dissolved materials; vesicles typically around 100 nm.
- Receptor-Mediated Endocytosis: Specific uptake triggered by receptor-ligand interactions.

Definition: Involves transporting materials across polarized cells from one surface to another without diffusion between cells (e.g., gut epithelium absorption).

Transport Mechanisms: Introduction of channels and transporter proteins for the movement of small molecules across cell membranes.
Passive Transport: Moves down chemical gradient without energy input.
Active Transport: Requires energy to move substances against concentration gradients.

Concept of Diffusion: Random movement from high to low concentration; requires understanding of entropy and energy changes.
Common Misconceptions: Molecules do not uniformly move from areas of high concentration; rather, diffusion is governed by random molecular motion and interactions.