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

Introduction to the Cytoskeleton

Anatomy & Physiology

2. Cell Chemistry & Cell Components

Introduction to the Cytoskeleton

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3:11 minutes

Problem 10

Textbook Question

George Palade's research group used the pulse–chase assay to elucidate the secretory pathway in pancreatic cells. If they had instead performed this assay on muscle cells, where would you expect the labeled proteins to end up during the chase? (Muscle cells consist primarily of actin and myosin filaments and have high energy demands for muscle contraction.)

Verified step by step guidance

Understand the pulse-chase assay: It involves 'pulsing' cells with a labeled compound (like a radioactive amino acid) to mark newly synthesized proteins, followed by a 'chase' with an unlabeled compound to track the movement of these proteins over time.

Consider the primary function of muscle cells: Muscle cells are specialized for contraction and consist mainly of actin and myosin filaments, which are crucial for this function.

Identify the secretory pathway: In the context of muscle cells, the secretory pathway would involve the synthesis of proteins in the rough endoplasmic reticulum (ER), their modification in the Golgi apparatus, and their transport to their final destinations.

Determine the likely destination of labeled proteins: Given the high energy demands and the structural role of actin and myosin in muscle cells, the labeled proteins would likely be incorporated into the contractile apparatus or involved in energy metabolism.

Conclude the expected outcome: During the chase phase, the labeled proteins would be expected to localize primarily to the sarcomeres, where actin and myosin are found, or to mitochondria, which are abundant in muscle cells to meet energy demands.

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Key Concepts

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

Pulse-Chase Assay

The pulse-chase assay is a technique used to study the synthesis and movement of proteins within cells. In this method, cells are first exposed to a labeled amino acid (the pulse) for a short period, allowing for the incorporation of the label into newly synthesized proteins. After this, the cells are transferred to a medium without the label (the chase), enabling researchers to track the fate of the labeled proteins over time as they move through various cellular compartments.

Secretory Pathway

The secretory pathway refers to the process by which proteins are synthesized, modified, and transported out of the cell or to specific locations within the cell. In pancreatic cells, this pathway is crucial for the secretion of digestive enzymes. Understanding this pathway helps in predicting where labeled proteins would localize in different cell types, such as muscle cells, which have distinct functions and protein trafficking mechanisms.

Muscle Cell Functionality

Muscle cells, primarily composed of actin and myosin filaments, are specialized for contraction and have high energy demands. The proteins synthesized in muscle cells are often involved in contraction and energy metabolism. During a pulse-chase assay, labeled proteins in muscle cells would likely be directed towards the sarcoplasmic reticulum and other structures involved in muscle contraction, rather than being secreted like in pancreatic cells.