5.6 Epithelial Transport Flashcards
Which way does the apical membrane face, and what might it have on it and why?
membrane faces the lumen of an organ and may have microvilli to increase surface area.
What is the job of tight junctions in epithelial cells?
separate the apical and basolateral membranes, preventing unregulated diffusion between cells.
which way does the basolateral membrane face, and what parts of the cell does it include?
membrane faces the extracellular fluid and includes the sides and base of the cell.
What does absorption mean in epithelial transport?
Absorption is the movement of material from the lumen to the extracellular fluid (e.g., nutrient absorption in the intestine).
What is secretion mean in epithelial transport?
Secretion is the movement of material from the extracellular fluid to the lumen
What does paracellular transport mean?
movement through junctions between nearby epithelial cells
How does glucose transport across epithelial cells occur (process into and out of cell)?
Glucose moves via SGLT (symporter) into the cell, then exits the cell through GLUT transporters.
What is the job of claudins in epithelial transport?
Claudins can form pores in tight junctions, allowing water and ions to move paracellularly.
What does transcellular transport mean?
involves molecules crossing both the apical and basolateral membranes of epithelial cells.
What drives the SGLT-mediated transport of glucose?
The sodium gradient provides the energy needed for glucose transport into the cell.
What happens to glucose if the basolateral Na+/K+ pump is inhibited?
Sodium cannot be pumped out, reducing the sodium gradient and halting glucose absorption.
What is transcytosis?
the process of moving large molecules across epithelial cells via endocytosis, vesicular transport, and exocytosis.
How do infants use transcytosis?
Infants absorb maternal antibodies from breast milk using transcytosis in the intestinal epithelium.
What happens if microtubules are disassembled in endothelial cells?
Transcytosis is disrupted because vesicles cannot be transported across the cell.
