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Renal Phys 5
WVSOM -- Renal Phys -- Basic Transport mechanisms; organic solutes
| Question | Answer |
|---|---|
| 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
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