Which of the following is action of insulin ?
**Core Concept**
Insulin is a hormone secreted by the beta cells of the pancreas, playing a crucial role in glucose metabolism. It facilitates the uptake of glucose by cells, thereby reducing blood glucose levels. Insulin signaling pathways involve the activation of key enzymes and receptors to regulate glucose homeostasis.
**Why the Correct Answer is Right**
Insulin binds to its receptor on the surface of cells, triggering a cascade of signaling events that ultimately lead to the activation of glucose transporter type 4 (GLUT4) translocation to the cell membrane. This enables glucose to enter the cell, reducing blood glucose levels and promoting glycogen synthesis and storage. The insulin signaling pathway also inhibits gluconeogenesis in the liver, further contributing to the regulation of blood glucose levels.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because insulin does not primarily act by increasing lipolysis (breakdown of fat). Insulin actually promotes lipogenesis (formation of fat) and inhibits lipolysis.
**Option B:** This option is incorrect because insulin does not primarily act by increasing the production of glucagon. In fact, insulin and glucagon have opposite effects on glucose metabolism, with insulin lowering and glucagon raising blood glucose levels.
**Option C:** This option is incorrect because insulin does not primarily act by increasing the breakdown of proteins. Insulin actually promotes protein synthesis and inhibits protein degradation, particularly in muscle cells.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that insulin resistance, a hallmark of type 2 diabetes, is characterized by impaired insulin signaling and reduced glucose uptake by cells. This knowledge is crucial for understanding the pathophysiology of diabetes and developing effective treatment strategies.
**Correct Answer: D. Promotes glucose uptake by cells.**