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Consider an erythrocyte with an internal glucose concentration of 0.1 mM and an external glucose concentration of 5 mM. Each of the following is true about GLUT1 transport of glucose across the plasma membrane into the cell except

A) Keq is always equal to 1.
B) ΔG depends on the concentration gradient.
C) inward movement is exergonic.
D) ΔG° is always equal to 0.
E) the rate of GLUT1 transport is faster than that of simple diffusion.

1 Answer

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Final answer:

The false statement about GLUT1 transport of glucose is that inward movement is exergonic. In reality, GLUT1 facilitates glucose movement down its concentration gradient without the input of energy, a process known as facilitated diffusion. When glucose concentrations are equal on both sides of the membrane, there is no net flow of glucose.

Step-by-step explanation:

The statement that is false about GLUT1 transport of glucose into an erythrocyte (red blood cell) is C) inward movement is exergonic. This is because GLUT1-mediated transport of glucose is via facilitated diffusion, which does not require energy and hence is not exergonic (energy-releasing). Instead, GLUT1 allows glucose to move down its concentration gradient, from an area of higher concentration to an area of lower concentration, without the use of energy, making the process energetically neutral.

If the concentration of glucose was equal inside and outside of the cell, there would be no net flow of glucose across the membrane; the system would be at dynamic equilibrium. While individual glucose molecules would still move across the membrane, the rate at which they enter the cell would be equal to the rate at which they leave, resulting in no net change in glucose concentration on either side of the membrane.

Facilitated diffusion is a type of passive transport where molecules like glucose use carrier proteins to move down a concentration gradient across the membrane. This differs from active transport where substances are moved against their concentration gradient and require energy to do so.

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