Question

What happens to the cell in terms of Glut4 after the binding of insulin to its receptor in the cell membrane? (total 100 words)

Answer 1

GLUT-4 (Glucose Transporter type 4) is a insulin dependant facilitated glucose transporter present in adipose tissue and striated muscle. When there is increased glucose concentration in the blood then insulin is secreted from the beta cells of pancreas. Insulin binds to insulin receptors on the cell membrane which activates tyrosine kinase domain. This leads to a cascade of signals in the cell which stimulates GLUT-4 to be expressed on the plasma membrane. Generally GLUT-4 is remains sequestrated in the intracellular vesicles of fat and muscle cells. The cascade process leads to fusion of these vesicles to the plasma membrane as a result the GLUT-4 protein become embedded into the membrane and become available for glucose transport. This will increase glucose absorption by this facilitated diffusion. Within the cell this glucose is rapidly phosphorylated by glucokinase/Hexokinase to for glucose-6 phosphate which enters into glycolytic pathway or is polymerized into glycogen. Thus the glucose is utilized either in ATP formation by glycolysis or is polymerized into glycogen for storage. The Glucose-6 phosphate cannot diffuse out of the cell which also serves to maintain the concentration gradient for the Glucose to enter into cell passively.

Summary of the process (for understanding) :-

Increased level of glucose in bloodstream.

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Insulin is secreted from the cells of pancreas

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Binds to the insulin receptors present on yhe cell membrane.

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Activation of tyrosine kinase domain and cascade of signals.

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Fusion of vesicles containing GLUT-4 with the plasma membrane.

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GLUT-4 gets imbedded in the cell membrane.

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Increased facilitated diffusion of glucose into the cell.

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This glucose is utilized to produce ATP by glycolysis or polymerization into glycogen for storage.

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Glucose level in the bloodstream is Decreased.