You consume a meal high in carbohydrates the night before a big race. Explain wh

Question

You consume a meal high in carbohydrates the night before a big race. Explain what type of mechanism will be used to transport glucose from your intestine to your muscles. The relative levels of glucose are provided below.

a. Gut lumen: low glucose       to      Intestinal epithelium cell: high glucose

b. Intestinal epithelium cell: high glucose     to          Interstitial fluid between intestinal cell and blood vessel: very low

(blood vessels have “clefs” that glucose fits through to enter blood by bulk flow.)

c. Blood: high glucose   to    Muscle: low glucose

d. Na+ is required for the transport into the intestinal epithelium cell. Why? How is the level of Na+ kept low in the intestinal cell?

Explanation / Answer

The transport of glucose takes place through two methods, either facilitated diffusion or secondary active transport , depending upon the concentration of glucose in the cell.

a. Gut lumen: low glucose to Intestinal epithelium cell: high glucose- in case when there is low glucose in the cell, the mechanism that is used for transport of glucose is secondary active transport. This occurs when the concentration gradient is against the molecule. Thus, energy is utilised for the transport of glucose. The active transport uses sodium potassium gradients and the energy is provided through ATP hydrolysis.

b. Intestinal epithelium cell: high glucose to Interstitial fluid between intestinal cell and blood vessel: very low

in case when there is low glucose in the cell, the mechanism that is used for transport of glucose is secondary active transport. This occurs when the concentration gradient is against the molecule. Thus, energy is utilised for the transport of glucose. The active transport uses sodium potassium gradients and the energy is provided through ATP hydrolysis.

The reason why here acgive transport is used even after lower concentration in the blood and a favourable concentration gradient because the concentration of glucose in the gut is highly unstable and is subjective to the dietary intake and in such a case it is required to ensure that glucose always flows in the direction of bloodstream. Hence, active transport.

c. Blood: high glucose to Muscle: low glucose

The RBC or blood cells use facilitated diffusion to transport the glucose into the muscle. Since there is a positive concentration gradient, a uniporter system will be used, that would help in transport of the glucose.

d. Na+ is required for the transport into the intestinal epithelium cell :

Since the gut epithelium has fluctuating levels of glucose, which either increases which may either increase or decrease, thus to ensure that there is correct flow of glucose as and when required into the gut epithelium even after low concentration, the energy transport is required.

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