Membrane Transport (2) Flashcards
(22 cards)
What is the epithelia?
Layers of cells that separate external and internal environments and regulate movement of solutes to and from the body
What are the 2 types epithelia can be divided in to?
Adsorptive - driven by Na+
Secretory - driven by Cl-
What types of membrane are in the epithelia?
Apical - external facing
Basolateral - internal facing
What do leaky tight junctions do?
Provide the bulk movement of isosmotic solution - e.g. kidney proximal tubule, small intestine
What do tight tight junctions do?
Block significant paracellular movement of molecules and can withstand large osmotic gradients - e.g. kidney distal collecting duct
How does Na⁺ transport drive absorptive epithelia?
The Na⁺-K⁺-ATPase pump maintains a low intracellular Na⁺ concentration, creating a gradient for Na⁺-driven solute uptake across the basolateral membrane
What happens when the Na⁺-K⁺-ATPase is inhibited by ouabain?
Intracellular Na⁺ increases, disrupting Na⁺-dependent transport and causing osmotic imbalances
What are the 3 principals of Na+ and absorptive epithelia?
1) Cell Na+ is kept low by Na+K+-ATPase
2) Na+ ions move down electrochemical gradient into cell across apical membrane
3) Transepithelial movement of Na+ leaves lumen negatively charged to contraluminal side.
What is vectorial movement of Na+ dependent on?
Transporter proteins that are present in the apical membrane
What is vesicular transport?
Transport of large particles/fluid droplets through membrane in vesicles using ATP
What are the 3 major types of vesicular transport endocytosis?
1) Receptor-mediated endocytosis
2) Pinocytosis
3) Phagocytosis
What is receptor-mediated endocytosis?
A selective process that involves the formation of vesicles at the surface of the membrane
What are 4 alternative functions of endocytotic vesicles?
1) Transcellular transport
2) Endosomal processing
3) Recycling the membrane
4) Destroying engulfed materials
What is pinocytosis?
Taking in droplets of ECF which is not a selective process where the membrane caves in, then pinches off into the cytoplasm as a pinocytotic vesicle
What is vesicular transport involving exocytosis?
Secreting material/replacement of plasma membrane
What group of disorders does the dysfunction of ion channels lead to?
Channelopathies
What can membrane transport failure/dysfunction arise from?
1) Mutations in gene promoter region
2) Mutations in the coding region
3) Defective regulation of transporter activity
4) Auto-antibodies to transport protein
5) Inappropriate location
6) Targets of a large, diverse group of toxins
What is an example of Channelopathies?
Cardiac channelopathy = long QT syndrome
What is an example of a membrane carrier disease?
Hartnup - results from impaired transports of AAs across epithelial cells of kidney proximal tubules and intestinal mucosa
What stages is mitosis divided into?
Interphase - preparation for cell division (G1, S and G2)
Metaphase - cell division (prophase, metaphase, anaphase, telophase)
Exiting cell division cycle - G0
What is apoptosis?
Regulated cell death where chromatin condenses and fragments organelles
Phagocytosis of apoptotic bodies formed
What is the role of CFTR in Cl⁻ secretion?
CFTR (ABC transporter) actively transports Cl⁻ into the lumen, crucial for fluid secretion in organs like the lungs and pancreas
