Which statement is TRUE regarding binding described by a hyperbolic binding curv
ID: 85510 • Letter: W
Question
Which statement is TRUE regarding binding described by a hyperbolic binding curve? When the concentration of ligand-receptor complex is equal to K_d, then fraction occupancy is 50%. The value of K_d may be different for the same receptor with different ligands. The binding curve applies only before equilibrium has been reached. The slope of the curve is the steepest for high ligand concentrations. All of the above are false. Fructose 1, 6-bisphosphate (FBP) and phosphoenol pyruvate (PEP) are each synthesized by transfer of a phosphate group from ATP to a precursor molecule; equilibrium constants (K) are indicated: Fructose 6-phosphate + ATP Equilibrium FBP + ADP K = 290 for FBP synthesis Pyruvate + ATP Equilibrium PEP + ADP K = 3.3 times 10^-6 for PEP synthesis Cellular concentrations are: [Fructose 6-phosphate] = 87 mu M, [FBP] = 22 mu M, [pyruvate] = 50 mu M, [PEP] = 20 mu M, [ATP] = 2mM, [ADP] = 0.2 mM. Which statement is TRUE regarding the spontaneous direction of these two reactions? FBP and PEP would both be consumed. FBP and PEP would both be synthesized. FBP would be consumed but PEP would be synthesized. FBP would be synthesized but PEP would be consumed.Explanation / Answer
2. Ans – A1
Because of the dissociation constant KD is commonly referred to - the value of KD is equal in magnitude to the concentration of ligand where half the protein molecules are bound to ligand at equilibrium. Therefore the value of KD is measured easily by measuring the fraction of protein molecules which are bound to ligand. f, the fractional saturation or fractional occupancy of the ligand binding sites in the protein molecules if it can bind to one ligand molecule then f is the ratio of the number of protein molecules which have ligand and bound to them to the total number of protein molecules.
f = concentration of protein with ligand bound: total protein concentration =
When the ligand concentration is equal in magnitude to the value of the dissociation constant, then the value of the fractional saturation, f,
f = [L]/ [L] + KD ; when [L] = KD
f = KD /KD + KD = 1 /2
From the above equation, when half the protein molecules in the solution have ligand bound to them, then the value of the ligand concentration is equal to the dissociation constant.
A2) The value of KD depends, in turn, on the temperature. That is, the dissociation “constant” is a constant only if the temperature is maintained at a constant value. Receptor affinity for ligand is defined the dissociation constant, Kd:
A3. value of Kd means that the equilibrium favors the complex
A4. The slope factor is a number that describes the steepness of the curve. The slope of the curve is the steepest for low ligand concentarion.
3. Ans – A3
1.The first step of gluconeogenesis is convert pyruvate to phosphoenolpyruvic acid (PEP by using several enzymes required
2.Generate fructose-6-phosphate from fructose-1,6- bisphosphate by the help of enzyme that Fructose 1,6-bisphosphatase.
3.The last step is the conversion of glucose-6-P to glucose with the enzyme glucose-6-phosphatase.
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