Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

2. Cell Chemistry & Cell Components

Endomembrane System: Protein Secretion

Anatomy & Physiology

2. Cell Chemistry & Cell Components

Endomembrane System: Protein Secretion

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1:22 minutes

Problem 16

Textbook Question

Describe the pathway of the protein hormone insulin from its gene to its export from a cell of your pancreas.

Verified step by step guidance

The process begins in the nucleus of the pancreatic beta cell, where the insulin gene is transcribed into messenger RNA (mRNA).

The mRNA exits the nucleus through the nuclear pores and enters the cytoplasm, where it binds to a ribosome on the rough endoplasmic reticulum (ER).

Translation occurs on the rough ER, where the ribosome synthesizes the insulin precursor, preproinsulin, which is then translocated into the lumen of the ER.

Inside the ER, preproinsulin undergoes folding and cleavage to form proinsulin, which is then transported to the Golgi apparatus for further processing.

In the Golgi apparatus, proinsulin is cleaved into mature insulin and C-peptide, packaged into secretory vesicles, and eventually exported from the cell via exocytosis in response to glucose stimulation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gene Expression

Gene expression is the process by which information from a gene is used to synthesize a functional gene product, typically a protein. In the case of insulin, the gene encoding this hormone is transcribed into messenger RNA (mRNA) in the nucleus of pancreatic beta cells. This mRNA then undergoes processing and is transported to the cytoplasm, where it serves as a template for protein synthesis.

Protein Synthesis

Protein synthesis involves two main processes: transcription and translation. After mRNA is produced, ribosomes in the cytoplasm translate the mRNA sequence into a polypeptide chain, which folds into the functional insulin protein. This process is crucial for the production of insulin, which regulates glucose levels in the blood.

Protein Secretion

Protein secretion is the process by which proteins are transported out of a cell. For insulin, once synthesized and properly folded in the endoplasmic reticulum, it is packaged into vesicles that travel to the Golgi apparatus for further processing. Finally, insulin is secreted from the pancreatic beta cells into the bloodstream in response to elevated blood glucose levels.