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Renal Phys 5

WVSOM -- Renal Phys -- Basic Transport mechanisms; organic solutes

QuestionAnswer
What are the 3 transport mechanisms? diffusion, channel and transports
What is the difference between a uniporter and a channel? tiny hole vs. a vestibule
How is facilitated diffusion different form diffusion? solute moves thru a transporter rather than thru a membrane
What is primary activce transport? MOVEMENT UPHILL AGAINST AN ELECTGROCHEMICAL GRADIENT
What is secondary active transport? use the downhill movemement of one solute to move another. Can be an antiport or a symport
What is a symporter? transporter moving the molecules in the same direction
What is an antiporter? transporter moving the molecules in opposite directions
What is endocytosis? attachment to membrane; membrane folds around to form a vesicle; intracellular processes degrade the vesicle contents
What is transcytosis? endocytosis at one membrane plus travel to the opposite membrane followed by exocytosis at that membrane
All transport requires what? energy
What are the organic solutes? urea, glucose, proteins and peptides, carboxylates
What is the renal handling of urea? filtered, reabsorbed, secreted and reabsorbed again (HE IS SO CONFUSED)
Where does reabsorption of urea occur? proximal tubule and the medullary collecting duct
How is urea generated? the liver generates urea from NH4+
Why is urea important in the kidney? it is both a waste substance and it is important in creation of medullary osmotic gradient that is necessary for concentration and dilution of urine
What is normal BUN? 7-18 mg/dl
What happens to urea with low urine flow? more urea is reabsorbed and less excreted
What happens with high urine flow? less urea reabsorbed, more excreted
What happens to water in the proximal tubule? it is reabsorbed leaving some urea behind and creates a concentration gradient for urea to move both transcellular and paracellular
Urine transport depends on _____________ concentration differences.
In renal disease, low GFR leads to… low urine flow, increase in urea retention and increased BUN
What happens to glucose in the kidney? it is freely filtered and is reabsorbed almost 100% in the proximal tubule
How is glucose transported? transcellular thru SGLT transporters and secondary active transport with Na. It is also transported via facilitared diffusion from Glut 2 and Glut 1
Where is Glut 2 tranporters in the kidney? early proximal tubule
Where is Glut 1 transporters in the kidney? late proximal tubule
What is the threshold of Glucose before it is not reabsorbed? 200mg/dl
How is glucose reabsorption limited? it is a Tubular maximum limited system
What is Tm? tubular maximum. It is the point where the filtered load of clucose at which the transporters will be overwhelmed (saturated) and starts to spill into the urine
What is splay? represents all of the nephrons reaching the Tm at different tiems depending on how large their glomerulus is and how many transporters they have expressed
What is the clearance of glucose before Tm? 0
A 50% decrease in GFR leads to a ____________ in plasma creatinine. INCREASE
Why is BUN not as clean for renal disease as creatinine? urea production is nto constant
What will elevate a BUN without it being related to the kidneys? high protein diet or enhanced tissue breakdown
What will cause a dcrease in urea production and a decrease in BUN? low protein diet or liver disease
Tm = 400mg/min, GFR is 125 ml/min and plasma glucose is 350 mg/dl. What is the filtered load of glucose and will there be spillover? Fl=Px X GFR = 3.5 X 125 = 437.5 so there will be spill over!
How much of amino acids filtered are reabsorbed? 98%
Why is so much amino acids reabsorbed? they need to be conserved
What is the Tm of AA compared to the Tm of glucose? Tm of AA is much lower than glucose so you wills ee protein in the urine if the plasma levels start to increase very much
What happens to carboxylates in the kidney? vertually all of them are reabsorbed because they are important to the kreb cycle
What is the pH dependence of excretion? Many substances are weak acids or bases so at a given pH, the total amount of each one is split between a neutral form and an ionized form. Highly acidic urine tends to increase passive reabsorption of weak acids
Created by: tjamrose