2 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 ofNa+Substrate VmaxL-Leucine 420D-Leucine 310L-Valine 225K₁ (MM)0.244.70.31Uptake in absence ofNa+Vmax23519K₁ (MM)0.244.70.31Select the statements that describe the properties and mechanism of the leucine transporter.Since the Vmax for all three substrates is lower in the absence of Na+, the leucine transporter cotransports Na+ and theamino acid.The higher K for D-leucine suggests that the leucine transporter binding site affinity depends on the orientation ofgroups on the x carbon of the amino acid.Since the K, for each substrate remains approximately the same in the presence and absence of Na+, the leucinetransporter does not require Na+ to transport amino acids.The high Vmax for D-leucine suggests that the leucine transporter binding pocket preferentially binds D-leucine overL-leucine and L-valine.The similar K, values for L-leucine and L-valine suggest that the binding site in the leucine transporter recognizes theside chains of both amino acids.

"Since the Vmax for all three substrates is lower in the absence of Na+, the leucine transporter cotransports Na+ and the amino acid."This statement is consistent with the observation. Vmax is the maximum rate of substrate transport, and the fact that Vmax is lower in the absence of Na+ implies that Na+ is involved in the transport mechanism. This supports the idea of cotransport, where Na+ and the amino acid are transported together."The higher Kt for D-leucine suggests that the leucine transporter binding site affinity depends on the orientation of groups on the alpha carbon of the amino acid."This statement is not accurate. The Kt (Michaelis-Menten constant) reflects the substrate concentration at which the transporter is working at half of its maximum velocity. A higher Kt indicates lower substrate affinity, but it doesn't necessarily indicate dependence on the orientation of groups on the alpha carbon. It simply implies that D-leucine has a lower binding affinity for the transporter compared to L-leucine 3."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."This statement is not supported by the data. The Kt values are different in the presence and absence of Na+, indicating that Na+ does affect the transporter's affinity for amino acids. The change in Kt suggests that Na+ is involved in the binding process or conformational changes that affect the transporter's interaction with substrates.4. "The high Vmax for D-leucine suggests that the leucine transporter binding pocket preferentially binds D-leucine over L-leucine and L-valine."This statement is not accurate. Vmax is a measure of the maximum rate of transport, not substrate binding affinity. The higher Vmax for D-leucine indicates a higher transport capacity but doesn't necessarily imply a preference for D-leucine in the binding pocket.5. "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."This statement is accurate. The similar Kt values for L-leucine and L-valine imply that the transporter's binding site can accommodate both amino acids with similar affinity. This suggests that the side chains of L-leucine and L-valine are recognized similarly by the leucine transporter.Statements 1 and 5 are consistent with the data, while statements 2, 3, and 4 do not accurately represent the information provided in the table.1. "Since the Vmax for all three substrates is lower in the absence of Na+, the leucine transporter cotransports Na+ and the amino acid."This statement is consistent with the data provided. In the absence of Na+, the Vmax values decrease, suggesting that Na+ is involved in the transport process.5."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."This statement is accurate. The similar Kt values for L-leucine and L-valine suggest that the binding site in the leucine transporter can accommodate both amino acids with similar affinity.