18 Aug, 2024
· Biology

Which of the following hormones corrects a hyperglycemic state

  • Insulin
  • Epinephrine
  • Cortisol
  • Glucagon
Short Answer
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Long Explanation

Explanation

Insulin

Insulin is the hormone responsible for correcting a hyperglycemic state. When blood glucose levels rise significantly, the pancreas secretes insulin to help lower these levels.

Mechanism of Action

Insulin facilitates the uptake of glucose into cells, especially muscle and fat cells, and inhibits the production of glucose by the liver. It also promotes the storage of glucose in the form of glycogen within the liver and muscles.

The key reactions can be summarized by the following equations:

Glucose→insulinglycogen (in liver and muscle)\text{Glucose} \xrightarrow{\text{insulin}} \text{glycogen (in liver and muscle)}

Additionally, insulin inhibits gluconeogenesis and glycogenolysis:

Gluconeogenesis (liver)←inhibition by insulin\text{Gluconeogenesis (liver)} \xleftarrow{\text{inhibition by insulin}} No glucose production\text{No glucose production} Glycogenolysis (liver)←inhibition by insulin\text{Glycogenolysis (liver)} \xleftarrow{\text{inhibition by insulin}} No glucose release \text{No glucose release}

Important Effects

  • Increased Glucose Uptake: Cells take in more glucose, lowering blood sugar levels.
  • Glycogenesis: Promotes the formation of glycogen from glucose.
  • Inhibition of Gluconeogenesis and Glycogenolysis: Prevents the liver from producing more glucose.

Summary

Insulin is crucial in maintaining normal blood glucose levels and preventing hyperglycemia.

Verified By
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Rebecca Green

Biology and Health Content Writer at Math AI

Rebecca Green, who recently completed her Master's in Biology from the University of Cape Town, works as a university lab teaching assistant and a part-time contract writer. She enjoys making biology fun and accessible through engaging content.

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Concept

Insulin'S Role In Glucose Uptake And Storage

Explanation

Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood glucose levels. When you consume food, especially carbohydrates, your body breaks it down into glucose, which then enters the bloodstream.

Mechanism of Glucose Uptake

Insulin facilitates the uptake of glucose into cells, particularly in the liver, muscle, and adipose (fat) tissues. Here's a simplified mechanism of how it works:

  1. Secretion: Upon detecting a rise in blood glucose levels, the pancreas secretes insulin.

  2. Receptor Binding: Insulin binds to specific receptors on the surface of target cells.

  3. Intracellular Signaling: This binding triggers a cascade of intracellular signals that promote the insertion of glucose transporter proteins (GLUT4) into the cell membrane.

  4. Glucose Uptake: The transporters then facilitate the entry of glucose into the cell, reducing the amount of glucose in the bloodstream.

Biochemical Pathway:

  1. Insulin binds to the insulin receptor (IR), which is a tyrosine kinase receptor.
  2. This triggers autophosphorylation of the receptor and subsequent phosphorylation of Insulin Receptor Substrates (IRS).
  3. Activated IRS initiates a series of downstream signaling events, primarily involving Phosphatidylinositol 3-kinase (PI3K) and Akt.
  4. One crucial effect is the translocation of GLUT4-containing vesicles to the cell membrane, allowing glucose to enter the cell.
IR + Insulin→IR∗(activated)IR∗+IRS→IRS-P(phosphorylated IRS)IRS-P→Activates PI3K→→Activates AktAkt→Translocates GLUT4 to membrane\begin{aligned} &\text{IR + Insulin} \rightarrow \text{IR}^* (\text{activated}) \\ &\text{IR}^* + \text{IRS} \rightarrow \text{IRS-P} (\text{phosphorylated IRS}) \\ &\text{IRS-P} \rightarrow \text{Activates PI3K} \rightarrow \\ & \rightarrow \text{Activates Akt} \\ &\text{Akt} \rightarrow \text{Translocates GLUT4 to membrane} \end{aligned}

Role in Storage

Once glucose enters the cells, insulin also promotes its storage:

  • In the Liver: Insulin stimulates the enzyme glycogen synthase, which converts glucose to glycogen for storage.
Glucose→Glycogen (via Glycogen Synthase)\text{Glucose} \rightarrow \text{Glycogen (via Glycogen Synthase)}
  • In the Muscles: Similar to the liver, muscles store glucose as glycogen.
  • In Adipose Tissue: Insulin facilitates the conversion of glucose into fatty acids and triglycerides for long-term energy storage.

Summary

Insulin is essential for maintaining glucose homeostasis by enabling glucose uptake into cells and promoting its storage as glycogen in the liver and muscle tissues, and as fat in adipose tissues. This regulatory mechanism ensures that blood glucose levels remain within a healthy range and that energy is available for future use.

Concept

Inhibition Of Gluconeogenesis And Glycogenolysis

Inhibition of Gluconeogenesis and Glycogenolysis

Gluconeogenesis and glycogenolysis are essential metabolic pathways that help maintain blood glucose levels. Gluconeogenesis is the process whereby glucose is synthesized from non-carbohydrate sources, while glycogenolysis is the process of breaking down glycogen into glucose.

Gluconeogenesis

Key Enzymes: The rate-controlling steps in gluconeogenesis involve enzymes such as:

  • Pyruvate carboxylase
  • Phosphoenolpyruvate carboxykinase (PEPCK)
  • Fructose-1,6-bisphosphatase
  • Glucose-6-phosphatase

The overall reaction for gluconeogenesis is:

2Pyruvate+4ATP+2GTP+2NADH+2 \text{Pyruvate} + 4 \text{ATP} + 2 \text{GTP} + 2 \text{NADH} + +6H2O→Glucose+4ADP+2GDP++ 6 \text{H}_2\text{O} \rightarrow \text{Glucose} + 4 \text{ADP} + 2 \text{GDP} + +6Pi+2NAD++ 6 \text{P}_i + 2 \text{NAD}^+

Glycogenolysis

Key Enzymes: Glycogenolysis involves the enzymes:

  • Glycogen phosphorylase
  • Debranching enzyme
  • Phosphoglucomutase

The reaction can be simplified as:

Glycogen+Pi→Glucose-1-phosphate+\text{Glycogen} + \text{Pi} \rightarrow \text{Glucose-1-phosphate} + +Glycogenn−1+ \text{Glycogen}_{n-1}

Inhibition Mechanisms

Hormonal Regulation: Insulin is a primary regulator that inhibits both processes:

  • Gluconeogenesis: Inhibition of key enzymes like PEPCK and glucose-6-phosphatase.
  • Glycogenolysis: Inhibition of glycogen phosphorylase activity.
Insulin→Decreased gene expression of PEPCK\text{Insulin} \rightarrow \text{Decreased} \ \text{gene expression of PEPCK} and glucose-6-phosphatase\text{and glucose-6-phosphatase} Insulin→Activation of glycogen synthase\text{Insulin} \rightarrow \text{Activation of glycogen synthase}

Allosteric Regulation: Molecules like fructose-2,6-bisphosphate act as potent inhibitors of gluconeogenesis by inhibiting fructose-1,6-bisphosphatase.

Fructose-2,6-bisphosphate→\text{Fructose-2,6-bisphosphate} \rightarrow →Inhibition of fructose-1,6-bisphosphatase\rightarrow \text{Inhibition of fructose-1,6-bisphosphatase}

Applications and Importance

The inhibition of these processes is particularly vital in conditions like diabetes where excess glucose production can lead to hyperglycemia. Understanding how these pathways are regulated helps in designing therapeutic strategies for managing blood sugar levels effectively.

Conclusion

Inhibiting gluconeogenesis and glycogenolysis is essential for the metabolic balance, especially under conditions where blood glucose needs to be tightly regulated, thus emphasizing the significant roles of hormonal and allosteric regulators in these pathways.