Lecture 6 Block 2 Flashcards
(19 cards)
What does saturability mean regarding Carrier-Mediated Transport?
There are a finite number of transporters AND each transporter has a finite turnover
What does measuring Kt and Jmax mean? (3 things)
- Provides a measure of transport ‘capacity’ and the extent to which it is acheived
- Since Kt is a ‘constant’ for a given transport protein, it provides a basis for comparison of different processes. Kt is clearest functional parameter reflecting transport structure.
- Physiological manipulation of Jmax and/or Kt provides information about regulatory mechanisms at work.
What is the clearest functional parameter reflecting transport structure?
Kt
What is Kt?
Kt is a constant (often called “Michaelis constant”) and is equal to the substrate concentration that produces “half-maximal” transport.
What is Jmax?
Jmax is the maximal rate of transport (reflecting saturation of the process)
What are the diagnostics of Carrier-Mediated transport?
Saturability
Selectivity
What does selectivity mean?
Each transport protein can ‘accept’ a limited range of chemical structures as substrates
What is competitive inhibition?
The combined influence of saturability and selectivity
What is noncompetitive inhibition?
The impact of ‘killing a transporter’
What is the overall kinetic response of a carrier-mediated transport system to the presence of a competitive inhibitor?
- An increase in apparent Kt
2. No change in Jmax
What is the overall kinetic response of a carrier-mediated transport system to the presence of a non-competitive inhibitor?
- A decrease in Jmax
2. No change in Kt
What tissues are GLUT1 transporters located in?
RBCs, endothelial
What tissues are GLUT2 transporters located in?
Liver, Pancreatic Beta-cells, basolateral membrane intestine and kidney
What tissues are GLUT3 transporters located in?
Neuronal
What tissues are GLUT4 transporters located in?
Muscle, fat
What tissues are GLUT5 transporters located in?
Intestines
What relationship does the Michaelis-Menten equation show?
That between substrate concentration and the rate of transport (revealing the “saturation” of that rate)
At any concentration what does the presence of a competitive inhibitor do to transport rates?
The presence of a competitive inhibitor reduces substrate transport rates.
If competitive inhibitor rates stay constant and substrate concentration increases… what happens?
If substrate concentration increases enough and the competitive inhibitor concentration remains constant then the substrate can reach the normal maximal rate of transport (Jmax)
