Question

Which of these statements about the hormone insulin is true? a. It is secreted by alpha cells in the pancreatic islets. b. It is secreted in response to a rise in blood glucose. c. It stimulates the production of glycogen and fat. d. Both \(a\) and \(b\) are true. e. Both \(b\) and \(c\) are true. Match the hormone with the primary agent that stimulates its secretion.

Short answer

e. Both \(b\) and \(c\) are true.

Step-by-step solution

Examining option a

Option a states that insulin is secreted by alpha cells in the pancreatic islets. This statement is incorrect. Insulin is produced and secreted by beta cells in the pancreatic islets, not alpha cells. Alpha cells secrete another hormone called glucagon, which opposes the action of insulin.

Examining option b

Option b states that insulin is secreted in response to a rise in blood glucose. This statement is true. When blood glucose levels increase, such as after a meal, insulin is released from the beta cells in the pancreas to facilitate the uptake and storage of glucose in muscle, fat, and liver cells.

Examining option c

Option c states that insulin stimulates the production of glycogen and fat. This statement is true. Insulin promotes the synthesis of glycogen and fat in the body. In the liver, it stimulates the conversion of glucose to glycogen. In adipose tissues, it facilitates the storage of glucose as fat.

Examining options d and e

Option d states that both statements \(a\) and \(b\) are true, and option e states that both statements \(b\) and \(c\) are true. As we've determined from our analysis, option a is false, while options b and c are true. Therefore, option d is incorrect, and option e is correct. Hence, the correct answer is: e. Both \(b\) and \(c\) are true.

Key concepts

Glucose Metabolism

Glucose metabolism is a critical process that ensures the body's cells have enough energy to function properly. It refers to the way our body uses glucose, which is a simple sugar, as a primary energy source. When we eat foods containing carbohydrates, they are broken down into glucose. This glucose is then absorbed into the bloodstream, causing blood glucose levels to rise.

In response, the pancreas releases insulin, a hormone that helps cells absorb glucose. Once inside the cells, glucose can be used immediately for energy or stored as glycogen in the liver and muscles for later use. Insulin plays a key role in regulating this process, ensuring that glucose is distributed effectively so the body maintains energy balance. Without insulin's regulatory role, glucose cannot be properly utilized, leading to conditions such as diabetes.

• Insulin facilitates glucose uptake in muscle and fat cells.
• Excess glucose is stored as glycogen in the liver.
• Insulin reduces blood glucose levels by aiding cell absorption.

Pancreatic Islets

The pancreatic islets, also known as the islets of Langerhans, are tiny clusters of cells in the pancreas imperative for regulating blood sugar levels. Despite their small size, these islets perform vital functions through their hormone-secreting activities.

These clusters contain different types of cells, each responsible for producing specific hormones that play crucial roles in maintaining glucose balance. The primary hormones include insulin, glucagon, and somatostatin. Each cell type has distinct functions:

• Beta cells, which make up the majority of the islets, produce insulin.
• Alpha cells secrete glucagon, which increases blood glucose levels.
• Delta cells produce somatostatin that regulates hormone secretion within the pancreas.

The coordination among these cells ensures a fine balance of glucose levels in the bloodstream, preventing both hyperglycemia and hypoglycemia.

Beta Cells

Beta cells play a crucial role in the body's response to glucose fluctuations. Located within the pancreatic islets, these cells are the primary producers of insulin. Beta cells are highly responsive to changes in blood glucose levels, which rise after consuming carbohydrates.

When glucose levels elevate, beta cells secrete insulin, which encourages glucose uptake by tissues such as the liver, adipose tissue, and muscle cells. This action lowers blood sugar levels back to normal. Inefficient functioning or destruction of beta cells leads to inadequate insulin production, significantly affecting blood glucose control and leading to diabetes.

• Beta cells detect high glucose levels and release insulin.
• They are crucial for converting glucose into energy or storing it.
• Their malfunctioning is a key factor in diabetes development.

Maintaining healthy beta cell function is essential for proper insulin production and effective glucose management.