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Questions and Answers
What does the smooth endoplasmic reticulum primarily synthesize?
What does the smooth endoplasmic reticulum primarily synthesize?
Which organelle is continuous with the perinuclear space?
Which organelle is continuous with the perinuclear space?
Which of the following cells is most likely to have a high abundance of rough endoplasmic reticulum?
Which of the following cells is most likely to have a high abundance of rough endoplasmic reticulum?
What is the primary structural feature of cisternae in the endoplasmic reticulum?
What is the primary structural feature of cisternae in the endoplasmic reticulum?
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What percentage of the total volume of a cell is occupied by the endoplasmic reticulum?
What percentage of the total volume of a cell is occupied by the endoplasmic reticulum?
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Which type of endoplasmic reticulum is characterized by the presence of ribosomes?
Which type of endoplasmic reticulum is characterized by the presence of ribosomes?
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What is the function of the vesicle structures in the endoplasmic reticulum?
What is the function of the vesicle structures in the endoplasmic reticulum?
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Which of the following best describes the composition of the membrane of the endoplasmic reticulum?
Which of the following best describes the composition of the membrane of the endoplasmic reticulum?
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Study Notes
Endoplasmic Reticulum (ER)
- The ER is a network of flat and vesicular structures found within the cytoplasm of animal cells.
- It forms a continuous membrane with a single, large, convoluted lumen.
- It occupies approximately 12% of a cell's total volume.
- Connected to the nuclear envelope.
- The smooth ER (SER) is formed from the rough ER (RER) by the loss of ribosomes.
- The space between the ER membranes (intercisternal space) is continuous with the space between the nuclear membranes (perinuclear space).
Structure
- The ER is composed of three elements:
- Cisternae: Narrow, flattened, and unbranched structures typically found near the nucleus. They are parallel to each other and interconnected. They are present in cells with active synthetic roles.
- Tubules: Wider, tubular, and irregularly branched structures mainly found near the cell membrane. Each tubule is approximately 50-100μm in diameter. They lack ribosomes and are involved in glycogen metabolism, lipid, and steroid synthesis.
- Vesicles: Spherical or oval bodies scattered in the cytoplasm, ranging from 25-500μm in diameter.
Types
- Smooth Endoplasmic Reticulum (SER): Also known as the agranular ER. Lacks ribosomes attached to its membranes, thus appearing smooth. Primarily involved in lipid (including steroids) and glycogen metabolism. Examples include adipose cells, glycogen-storing cells of the liver, spermatocytes, and leucocytes.
- Rough Endoplasmic Reticulum (RER): Possesses ribosomes attached to its membranes, giving it a rough appearance. Abundant in cells actively engaged in protein synthesis, such as pancreatic cells, plasma cells, goblet cells, and liver cells.
Functions
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Smooth ER Functions:
- Lipid metabolism: Synthesis of phospholipids, cholesterol, and steroids.
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Description
This quiz covers the structure and functions of the Endoplasmic Reticulum (ER) in animal cells. It explores the differences between smooth and rough ER, as well as the structure of cisternae and tubules. Test your knowledge on cellular organelles and their roles!
