Glucose enters erythrocytes via a GLUT-1 uniporter. As the levels of glucose in the bloodstream decrease between meals, what happens to the glucose in the cells? A. Glucose leaves the cell through the GLUT-1 uniporter, traveling down the new concentration gradient. B. Glucose remains in the cell because uniporters can only transport in one direction. C. Glucose remains in the cell because the GLUT-1 uniporters are gated and the gates close at low glucose concentrations. D. Glucose remains in the cell because it has been phosphorylated and no longer has affinity forthe GLUT-1 uniporter.

A. Glucose leaves the cell through the GLUT-1 uniporter, traveling down the new concentration gradient.  

Explanation:

The Glucose transporter 1 (GLUT1) protein is a critical uniporter transporter that facilitates the movement of glucose molecules across the plasma membrane. The expression of GLUT1 is increased when glucose concentration is reduced and, inversely, GLUT1 expression is reduced when glucose levels are increased. The erythrocytes are cells that continuously require the supply of glucose from the blood plasma, this mechanism involves the function of GLUT1 that permits the energy-free passage of glucose by diffusion.

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cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!