Which of the following is/are true regarding glucose transport

[CMATT]

Homework Statement

Which of the following is/are true regarding glucose transport to the brain? There could be multiple answers.

a) Glucose uptake by the nerve cells of the brain is dependent on insulin
b) Greater concentrations of glucose in the blood should increase the rate at which glucose moves out of the capillaries in the brain
c) Given the same concentration gradients of glucose, the rate at which glucose is taken into nerve cells of the brain should be greater than the rate at which glucose moves from the intracellular fluid of intestinal cells to the extracellular fluid surrounding them
d) Increased rates of glucose conversion to either glycogen or fatty acids could decrease uptake by nerve cells of the brain

The Attempt at a Solution

So far, I chose answer D because if glucose is being taken up by the liver (glycogen storage) or adipocytes (triglycerides/fatty acids) then that means there is less glucose to be taken up by nerve cells in the brain

I did not choose answer A because I found somewhere that it GLUT3 is not dependent on insulin

The other ones I am not so sure about. If someone could please help me with this that would be much appreciated!

 

[nate808]

I would like to provide a more detailed and accurate response to the forum post.

a) Glucose uptake by the nerve cells of the brain is dependent on insulin
This statement is partially true. While insulin is not the only factor that regulates glucose uptake in the brain, it does play an important role. Insulin signaling increases the activity of glucose transporters, such as GLUT3, in the brain, leading to increased glucose uptake. However, there are also other factors, such as blood glucose levels and neuronal activity, that can independently regulate glucose uptake in the brain.

b) Greater concentrations of glucose in the blood should increase the rate at which glucose moves out of the capillaries in the brain
This statement is true. Glucose is transported from the blood into the brain through specialized transporters, such as GLUT1 and GLUT3, located on the surface of brain capillary endothelial cells. These transporters are regulated by glucose concentration gradients, such that higher blood glucose levels will lead to increased glucose transport into the brain.

c) Given the same concentration gradients of glucose, the rate at which glucose is taken into nerve cells of the brain should be greater than the rate at which glucose moves from the intracellular fluid of intestinal cells to the extracellular fluid surrounding them
This statement is also true. The transport of glucose from the blood into the brain is facilitated by specialized transporters, while the transport of glucose from the intracellular fluid of intestinal cells to the extracellular fluid surrounding them is mainly through diffusion. Therefore, the rate of glucose transport into the brain is typically higher than the rate of glucose transport in the intestinal cells.

d) Increased rates of glucose conversion to either glycogen or fatty acids could decrease uptake by nerve cells of the brain
This statement is also partially true. Glucose can be converted into glycogen or fatty acids in the liver or adipose tissue, respectively. This process can decrease the amount of glucose available in the blood for uptake by the brain. However, the brain also has the ability to synthesize its own glucose through a process called gluconeogenesis, which can counteract the decrease in glucose availability. Therefore, while increased rates of glucose conversion to glycogen or fatty acids may decrease uptake by nerve cells of the brain, it may not have a significant impact on overall brain glucose uptake.