Uptake in absence of Na* To gain insight into the mechanism of the leucine trans

Question

Uptake in absence of Na* To gain insight into the mechanism of the leucine transporter in intestinal epithelial cells, the rate of uptake of L-leucine, D-leucine, and L-valine was assayed in the presence and absence of Nat. The results of rate measurements are given in the table Uptake in presence of Na* SubstrateVmax Kt (mM) Vmax Kt (mM) L-Leucine420 0.24 D-Leucine 3104.7 L-Valine 225 0.31 0.24 4.7 0.31 23 Select the statements that describe the properties and mechanism of the leucine transporter. 19 The similar Kt values for L-leucine and L-valine suggest that the binding site in the leucine transporter recognizes the side chains of both amino acids Since the Kt for each substrate remains approximately the same in the presence and absence of Na*, the leucine transporter does not require Na* to transport amino acids The higher Kt for D-leucine suggests that the leucine transporter binding site affinity depends on the orientation of groups on the ? carbon of the amino acid Since the Vmax for all three substrates is lower in the absence of Na*, the leucine transporter cotransports Na* and the amino acid The high Vmax for D-leucine suggests that the leucine transporter binding pocket preferentially binds D-leucine over L-leucine and L-valine

Explanation / Answer

Correct options

a) true, The similar Kt values for L-leucine and L-valine suggest that the binding site in the leucine transporter recognizes the side chains of both amino acids.

b) false, it is not approx the same and transport will still require Na+

c)true, The higher Kt for D-leucine suggests that the leucine transporter binding site affinity depends on the orientation of groups on the carbon of the amino acid;

d)true Since the Vmax for all three substrates is lower in the absence of Na+, the leucine transporter cotransports Na and the amino acid.

e) this is false, this will not be preferential

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