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Questions and Answers
What is the primary function of the rough endoplasmic reticulum (RER)?
Which feature distinguishes rough endoplasmic reticulum (RER) from smooth endoplasmic reticulum (SER)?
Which type of cell would you expect to have a prominent rough endoplasmic reticulum?
What is one of the main functions of the smooth endoplasmic reticulum (SER) in the liver?
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Which feature is NOT characteristic of rough endoplasmic reticulum (RER)?
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How does the smooth endoplasmic reticulum (SER) differ in structure from the rough endoplasmic reticulum (RER)?
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Which of the following functions is associated with the rough endoplasmic reticulum (RER)?
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What role does the smooth endoplasmic reticulum (SER) play in muscle cells?
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What is the primary function of the sarcoplasmic reticulum in muscle cells?
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What process occurs primarily in the Golgi apparatus regarding proteins?
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What characterizes the Golgi apparatus's cis and trans faces?
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Which type of vesicles arise from the mature face of the Golgi apparatus?
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Why are lysosomes referred to as 'suicide bags'?
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Which enzyme activity is specifically used as a marker for lysosomes?
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What is the optimal pH level for the activity of the hydrolytic enzymes found in lysosomes?
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Where in the cell are primary lysosomes formed?
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What is the structure and function of the area where proteins are received in the Golgi apparatus?
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What is a key function of primary lysosomes in the cell?
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Which process is occurring when secretory vesicles release their contents outside the cell?
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Which statement correctly describes lysosomes?
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What is one of the roles of the Golgi apparatus in relation to glycosylation?
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What is the optimal pH for acid hydrolases found in lysosomes?
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What characterizes the transport vesicles that carry proteins from the RER to the Golgi apparatus?
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Which function is NOT associated with the Golgi apparatus?
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What is a key characteristic of the cisternae of rough endoplasmic reticulum (RER)?
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Which statement about the smooth endoplasmic reticulum (SER) is true?
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Which of the following cells would most likely have an abundant smooth endoplasmic reticulum (SER)?
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What is one function of the rough endoplasmic reticulum (RER)?
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Where do the functions of the smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER) overlap?
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Which statement accurately describes the appearance of the rough endoplasmic reticulum (RER)?
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What is a significant role played by the smooth endoplasmic reticulum (SER) in the adrenal glands?
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Which of the following best describes the composition of the cisternae in the smooth endoplasmic reticulum (SER)?
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Study Notes
Endoplasmic Reticulum (ER)
- A membranous organelle forming a network of interconnected channels called cisternae that extends from the nuclear membrane to the cell membrane.
- Two types: Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
- RER: Cisternae covered by ribosomes and polysomes giving it a rough, granular surface.
- SER: No attached ribosomes, giving it a smooth appearance.
- Both types are continuous with each other.
Rough Endoplasmic Reticulum (RER)
- Concerned with the synthesis of proteins, primarily for secretion outside the cell.
- Prominent in cells specialized for protein secretion, such as fibroblasts (synthesize collagen), plasma cells (synthesize antibodies).
- Light Microscopy (L/M): Basophilic due to the attached ribosomes.
- Electron Microscopy (E/M): Parallel cisternae continuous with the outer nuclear membrane, flattened in shape, and have attached ribosomes and polyribosomes.
Smooth Endoplasmic Reticulum (SER)
- Endoplasmic reticulum cisternae without attached ribosomes.
- Continuous with RER.
- Prominent in cells specialized for lipid biosynthesis, such as cells of the adrenal glands, testis, and ovary.
- L/M: Not basophilic.
- E/M: Cisternae are either tubular or vesicular in shape (not flattened). Smooth surface with no attached ribosomes.
Functions of the Rough Endoplasmic Reticulum (RER)
- Segregation of proteins synthesized by attached ribosomes.
- Initial glycosylation of proteins (addition of carbohydrates to the synthesized protein).
Functions of the Smooth Endoplasmic Reticulum (SER)
- General: Synthesizes phospholipids of the cell membrane.
- Liver cells: Involved in glycogen metabolism, detoxification of certain drugs and toxic substances (e.g., alcohol).
- Adrenal glands, Testis, and Ovary: Lipid biosynthesis (e.g., synthesis of steroid hormones like cortisone, male and female hormones).
- Muscle cells (Sarcoplasmic reticulum): Releases calcium ions during contraction and reuptakes them during relaxation.
Golgi Apparatus
- A membranous organelle involved in the secretion of proteins synthesized by the RER.
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Functions:
- Concentration, packaging, and storage of proteins to be secreted.
- Glycosylation of proteins (begins in RER and is completed in Golgi saccules).
- Formation of primary lysosomes.
- Synthesis of many glycosaminoglycans (GAGs) that form the extracellular matrix (ECM) of connective tissue.
- L/M: H&E staining: Unstained area near the nucleus (negative Golgi image). Silver staining: Appears dark brown.
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E/M: 4-10 saccules forming a stack. Each stack has two surfaces:
- Cis face (immature face, convex): Receives transfer vesicles carrying proteins from the RER.
- Trans face (mature face, concave): Releases secretory vesicles outside the cell.
- Transfer vesicles: Small vesicles that carry proteins from the RER to the immature face of the Golgi.
- Secretory vesicles: Large vesicles arising from the mature face, either secreted outside the cell (exocytosis) or remain in the cytoplasm as primary lysosomes.
Lysosomes
- Membranous organelles containing about 40 hydrolytic enzymes (acid hydrolases).
- Known as "suicide bags" due to their destructive potential.
- Acid hydrolases: Optimal activity at acidic pH (~5.0). Examples include proteases and phosphatases.
- Formation: Synthesized and segregated in the RER, transferred to the Golgi apparatus to form primary lysosomes.
- Site: Present in the cytoplasm of all cells. More abundant in cells with high phagocytic activity (macrophages).
- L/M: Enzyme histochemistry: Demonstration of acid phosphatase enzyme activity (marker of lysosomes).
Endoplasmic Reticulum (ER)
- A membranous network that extends from the nuclear membrane to the cell membrane.
- Formed of interconnected channels called cisternae (reservoirs).
- Two types: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).
Rough Endoplasmic Reticulum (RER)
- Cisternae are covered by ribosomes and polysomes, giving it a rough or granular surface.
- Involved in protein synthesis, mostly for secretion outside the cell.
- Prominent in cells specialized for protein secretion, such as fibroblasts (synthesizing collagen) and plasma cells (synthesizing antibodies).
- Parallel cisternae are continuous with the outer nuclear membrane.
- Cisternae are flattened in shape.
- Appears basophilic under a light microscope due to the attached ribosomes.
Smooth Endoplasmic Reticulum (SER)
- No attached ribosomes.
- Continuous with the RER.
- Cisternae are either tubular or vesicular in shape (not flattened).
- Prominent in cells specialized for lipid biosynthesis, such as cells of the adrenal glands, testis, and ovary. Also found in liver cells and muscle cells (sarcoplasmic reticulum).
- Not basophilic under a light microscope.
RER Functions
- Segregates proteins synthesized by attached ribosomes.
- Initial glycosylation of proteins (addition of carbohydrates to synthesized protein).
SER Functions
- Synthesizes phospholipids of the cell membrane.
- In liver cells:
- Glycogen metabolism.
- Detoxification of drugs and toxic substances (e.g., alcohol).
- In adrenal glands, testis, and ovary:
- Lipid biosynthesis (e.g., synthesis of steroid hormones, cortisone, male and female hormones).
- In muscle cells (sarcoplasmic reticulum):
- Releases calcium ions during contraction and reuptakes them during relaxation.
RER Products
- Proteins are transported to the Golgi apparatus for secretion outside the cell.
- Form primary lysosomes.
- Form integral proteins of the cell membrane.
Golgi Apparatus
- A membranous organelle involved in protein secretion synthesized by the RER.
Golgi Apparatus Functions
- Concentration, packaging, and storage of proteins for secretion.
- Glycosylation of proteins (begins in the RER and completes in Golgi saccules).
- Forms primary lysosomes.
- Synthesis of glycosaminoglycans (GAGs) that form the extracellular matrix (ECM) of connective tissue.
Golgi Apparatus Appearance
- Under light microscopy (H&E stain): Unstained area near the nucleus (negative image).
- Under light microscopy (Silver stain): Appears dark brown.
- Under electron microscopy: 4-10 saccules forming a stack. Each stack has two surfaces:
- Cis face: Immature face (convex), receives transfer vesicles carrying proteins from the RER.
- Trans face: Mature face (concave), releases secretory vesicles outside the cell.
Golgi Apparatus Vesicles
- Transfer vesicles: Small, carry proteins from the RER to the immature face of Golgi.
- Secretory vesicles: Large, arise from the mature face and either:
- Secreted outside the cell (exocytosis).
- Remain in the cytoplasm as primary lysosomes.
Lysosomes
- Membranous organelles containing about 40 hydrolytic enzymes (acid hydrolases).
- Called suicide bags.
- Acid hydrolases are optimally active at acidic pH (~5.0). Examples: proteases and phosphatases.
- Synthesized and segregated in the RER.
- Transferred to the Golgi apparatus to form primary lysosomes.
Lysosome Characteristics
- Present in the cytoplasm of all cells.
- More abundant in cells with great phagocytic activity (macrophages).
Lysosome Appearance
- Light microscopy: Enzyme histochemistry demonstrates acid phosphatase enzyme activity (marker of Lysosomes).
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Description
This quiz covers the structure and function of the Endoplasmic Reticulum (ER), including its two main types: Rough ER (RER) and Smooth ER (SER). Explore the role of RER in protein synthesis and the characteristics that distinguish it from SER, including their appearances under light and electron microscopy.
