Question

A. Acts mainly on liver cells B. Stimulate glycogenolysis C. Stimulate gluconeogenesis D. Reduces glucose uptake and utilization Which of the following is correct about the action of glucagon from the above statements? (a) \(\mathrm{A}\) and \(\mathrm{B}\) only (b) B and C only (c) \(\mathrm{A}, \mathrm{B}\) and \(\mathrm{C}\) only (d) All of these

Short answer

The correct option is (d) All of these.

Step-by-step solution

Analyze statement A

Statement A mentions that glucagon primarily acts on liver cells, which is true. Glucagon targets liver cells to increase blood glucose concentration by promoting the breakdown of glycogen into glucose.

Analyze statement B

Statement B talks about stimulation of glycogenolysis. This is also true, since glycogenolysis refers to the metabolic pathway leading to glucose release from stored glycogen in the liver.

Analyze statement C

Statement C is about stimulation of gluconeogenesis. Gluconeogenesis is the process of producing glucose from non-carbohydrate sources and is indeed stimulated by glucagon.

Analyze statement D

Statement D says that glucagon reduces glucose uptake and utilization. This is accurate since glucagon decreases glucose uptake in the liver, thereby increasing blood glucose levels.

Identify the correct option

With reference to these explanations, all four statements correctly describe the actions of glucagon. Thus, the correct answer to this problem is (d) All of these.

Key concepts

Glycogenolysis

Glycogenolysis is a crucial process that helps regulate blood sugar levels in the body. It involves the breakdown of glycogen, a stored form of glucose, into glucose molecules. This process primarily occurs in the liver cells and is stimulated by hormones like glucagon and adrenaline.
When blood sugar levels drop, glucagon is secreted by the pancreas and triggers glycogenolysis. It activates an enzyme called glycogen phosphorylase, which breaks down glycogen into glucose-1-phosphate. This is then converted into glucose-6-phosphate and finally into free glucose that is released into the bloodstream.
The importance of glycogenolysis cannot be understated, as it acts as a rapid response mechanism to maintain blood glucose levels during periods of fasting or intense physical activity. Without it, our body would struggle to manage energy supply, especially when intake from food is minimal.

Gluconeogenesis

Gluconeogenesis is a metabolic pathway that generates glucose from non-carbohydrate sources, such as amino acids and glycerol. This process occurs mainly in the liver and provides the body with glucose during prolonged fasting, starvation, or low carbohydrate intake.
Glucagon plays a significant role in stimulating gluconeogenesis, ensuring a continuous supply of glucose to organs such as the brain and red blood cells, which rely heavily on glucose for energy. It achieves this by increasing the expression of enzymes that drive gluconeogenesis, such as phosphoenolpyruvate carboxykinase and glucose-6-phosphatase.
While glycogenolysis provides a quick glucose supply, gluconeogenesis is vital for long-term glucose production, maintaining energy balance, and preventing hypoglycemia over extended periods without food intake.

Liver Function

The liver is an essential organ that performs numerous vital functions, one of the most important being the regulation of blood glucose levels. It achieves this through processes like glycogenolysis and gluconeogenesis.
The liver acts as a glucose reservoir, storing glycogen that can be converted into glucose when blood sugar drops. In addition, it is a site for gluconeogenesis, producing glucose from various precursors.
Besides glucose regulation, the liver also metabolizes nutrients absorbed from the digestive tract, detoxifies chemicals, and serves as a storage unit for vitamins and minerals. Without the liver's proper functioning, maintaining steady blood sugar levels and overall metabolic balance would be extremely challenging.

Blood Glucose Regulation

Blood glucose regulation is a complex process involving multiple hormones and organs, with glucagon and insulin being key players. Maintaining precise glucose levels is crucial for energy management and overall health.
The pancreas monitors blood glucose levels and secretes glucagon and insulin based on the body's needs. Glucagon raises blood glucose by stimulating glycogenolysis and gluconeogenesis in the liver, while insulin lowers glucose levels by promoting its uptake and utilization by body cells.
Imbalances in blood glucose regulation can lead to conditions like hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar), seen in diabetes. Therefore, understanding how glucagon and insulin work together to keep glucose levels in check is vital for managing these conditions effectively.