Cell Organelles II Quiz
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Questions and Answers

What does the endomembrane system include?

The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and plasma membrane.

What is the endoplasmic reticulum (ER)?

  • A network of membranes or intercommunicating channels within the cytoplasm (correct)
  • A single, large organelle responsible for protein synthesis
  • A series of flattened, membranous sacs involved in packaging proteins
  • A sac of hydrolytic enzymes that digest macromolecules

    • The rough endoplasmic reticulum (RER) has no ribosomes on its surface.

    False

    Which of these is a function of the smooth endoplasmic reticulum (SER)?

    <p>Lipid synthesis</p> Signup and view all the answers

    What are the four main types of protein modifications that occur within the Golgi complex?

    <p>Glycosylatlon (addition of carbohydrate), Sulfation (addition of sulfur), Phosphorylation (addition of phosphate), Proteolysis (cleavage of peptide bonds)</p> Signup and view all the answers

    What is the function of lysosomes?

    <p>Lysosomes are organelles that contain hydrolytic enzymes, which are responsible for breaking down macromolecules and cellular debris.</p> Signup and view all the answers

    Lysosomal enzymes are most active in the neutral pH of the cytosol.

    <p>False</p> Signup and view all the answers

    What are the three main types of lysosomes?

    <p>Primary lysosomes, secondary lysosomes, tertiary lysosomes</p> Signup and view all the answers

    Explain how an autophagolysosome is formed.

    <p>An autophagolysosome is formed when an autophagic vacuole, containing worn-out organelles, fuses with a lysosome.</p> Signup and view all the answers

    What are vacuoles, and what are their functions?

    <p>Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi apparatus. They primarily function in storage, waste removal, and maintaining cell turgor.</p> Signup and view all the answers

    Which of these is NOT a function of vacuoles?

    <p>Protein synthesis</p> Signup and view all the answers

    What type of vacuole is found in plant cells?

    <p>Mature plant cells typically contain a large central vacuole.</p> Signup and view all the answers

    Study Notes

    Cell Organelles II

    • Single-bound membrane organelles include the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
    • The endomembrane system encompasses the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane.
    • The endoplasmic reticulum (ER) is a network of interconnecting channels called cisternae, making up more than half of the total membranes in eukaryotic cells.
    • The ER extends from the outer nuclear membrane throughout most of the cytoplasm to the plasma membrane.
    • The ER's function is to move molecules through its cisternae (lumen/cavity) from one part of the cell to another.

    Types of Endoplasmic Reticulum

    • Rough ER (RER): RER has ribosomes on its surface and is prevalent in cells specialized for protein secretion, such as pancreatic acinar cells (digestive enzymes), fibroblasts (collagen), hepatocytes (albumins), and plasma cells (immunoglobulins).

    • Smooth ER (SER): SER lacks ribosomes and is prominent in Leydig cells of the testis (testosterone secretion), hepatocytes (detoxification), and other cells.

    Rough Endoplasmic Reticulum (RER) Function

    • RER is where proteins are synthesized, packaged, and then secreted.

    Smooth Endoplasmic Reticulum (SER) Function

    • Lipid synthesis: SER synthesizes phospholipids (major components of cellular membranes) and steroids or sex hormones (e.g., testosterone from Leydig cells).
    • Detoxification: SER enzymes (e.g., cytochrome P450 family) detoxify harmful molecules like alcohol, toxins, and drugs.
    • Bile processing: In liver cells, SER enzymes process bile components. Jaundice results from the accumulation of bilirubin or other pigments, which are usually metabolized and excreted as bile by SER enzymes.
    • Muscle contraction: SER in skeletal muscle cells (sarcoplasmic reticulum) releases and re-absorbs calcium ions (Ca2+) during muscle contraction/relaxation.

    Golgi Apparatus

    • The Golgi apparatus is a series of flattened membranous sacs (cisternae).
    • It receives vesicles containing proteins from the RER through its cis face.
    • Proteins undergo modification within the Golgi apparatus.
    • The Golgi apparatus has three parts:
      • Cis face: Receives incoming transport vesicles from RER.
      • Cisternae: Site of protein modifications.
      • Trans face: Releases secretory vesicles (containing modified proteins/vesicles).

    Protein Modifications within the Golgi Complex

    • Glycosylation: Addition of carbohydrates.
    • Sulfation: Addition of sulfur.
    • Phosphorylation: Addition of phosphate.
    • Proteolysis: Cleavage of peptide bonds.

    Lysosomes

    • Lysosomes are membranous sacs containing hydrolytic enzymes used by eukaryotic cells to digest macromolecules.
    • Lysosomal enzymes function best in the acidic pH of lysosomes.
    • Leakage of lysosomal contents into the cytosol (which has a near-neutral pH) inactivates lysosomal enzymes.
    • Excessive leakage can also lead to cell death via self-digestion.

    Types of Lysosomes

    • Primary lysosomes: Newly secreted from the Golgi apparatus and do not fuse with other vesicles.
    • Secondary (heterolysosomes): Form by the fusion of primary lysosomes with other vesicles, leading to the degradation of ingested material.
      • Phagolysosomes: Formed by the fusion of a phagocytic vacuole with a lysosome.
      • Multivesicular bodies: Created by fusing an endocytic vesicle (endosome) with a lysosome.
      • Autophagolysosomes: Formed by an autophagic vacuole (formed by autophagy, which targets worn-out organelles) fusing with a lysosome.
    • Tertiary lysosomes: Contain only indigestible material – residual bodies.

    Vacuoles

    • Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi apparatus.

    • Types of vacuoles:

      • Food vacuoles: Formed by phagocytosis (engulfment of food particles) in phagocytic cells (e.g., amoebas, macrophages).
      • Contractile vacuoles: Found in freshwater protists; they pump out excess water.
      • Plant vacuoles (plant cell):
        • Small vacuoles: Store organic compounds (e.g., proteins in seeds).
        • Plant defense vacuoles: Protect the plant from animals by housing poisonous/unpalatable compounds.
        • Pigment vacuoles: Contain pigments (e.g., red/blue pigments in petals to attract pollinators).
        • Central vacuole: Large central vacuole in mature plant cells, containing cell sap rich in minerals and other stored compounds.

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    Cell Biology Course (Bio-1101) Lect. 6: Cell Organelles II PDF

    Description

    Test your understanding of cell organelles and their functions with this quiz. Explore the roles of the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles in the endomembrane system. Assess your knowledge on the differences between rough and smooth endoplasmic reticulum and their significance in eukaryotic cells.

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