Final answer:
The glucose transporter passively mediates the movement of glucose across the plasma membrane through a process called facilitated diffusion using GLUT proteins. It allows glucose to move along its concentration gradient without the need for energy. Insulin can increase the number of GLUTs on the cell membrane to facilitate glucose uptake when necessary.
Step-by-step explanation:
The glucose transporter facilitates the passive movement of glucose across the plasma membrane via a mechanism known as facilitated diffusion. Glucose molecules are polar and cannot easily pass through the hydrophobic core of the plasma membrane without assistance. Instead, they rely on glucose transport proteins, or GLUTs, which provide a specific channel for glucose to move from areas of higher concentration (outside the cell) to areas of lower concentration (inside the cell), down its concentration gradient.
This process does not require energy because it is driven by the inherent concentration gradient of glucose across the membrane. Facilitated diffusion enables cells to acquire glucose necessary for cellular respiration and other metabolic processes without expending ATP (adenosine triphosphate), making it an efficient mode of nutrient uptake. Once inside the cell, glucose can be metabolized to extract energy or used in various biosynthetic pathways. GLUTs, as carrier proteins, increase their activity as the concentration of glucose rises until they reach a saturation point, beyond which they can no longer increase the rate of transport. This characteristic ensures that cells can regulate the uptake of glucose based on the availability of the sugar in the extracellular fluid. These transporters are essential for maintaining glucose homeostasis and their function can be influenced by hormones such as insulin, which increases the number of GLUTs on the cell membrane, facilitating further glucose uptake into cells when blood glucose levels are high.