Final answer:
The enzyme hexokinase is associated with the cytoplasmic portion of the glucose transporter and is crucial for phosphorylating glucose during the first step of glycolysis. Option A) hexokinase is the correct answer.
Step-by-step explanation:
The enzyme associated with the cytoplasmic portion of the glucose transporter is hexokinase. This enzyme plays a crucial role in the glycolysis pathway, where it catalyzes the first step by adding a phosphate group to glucose to form glucose-6-phosphate.
The use of ATP in this reaction ensures that the glucose molecule becomes unable to cross the cell's hydrophobic plasma membrane, effectively trapping it within the cell to facilitate its use in metabolic processes.
Hexokinase operates with a high affinity for glucose, enabling the cell to efficiently phosphorylate glucose even when glucose levels are low, thereby prioritizing glucose usage for tissues that need it the most.