Cell Biology: Organelles and Structures
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Questions and Answers

Which of the following statements accurately describes mitochondrial structure?

  • Mitochondria possess a single membranous layer.
  • The outer mitochondrial membrane is smooth and permeable. (correct)
  • The inner mitochondrial membrane is rigid and inflexible.
  • Mitochondria contain no DNA.

    • What is the primary function of lysosomes among membranous organelles?

  • Storage and breakdown of cellular waste. (correct)
  • Synthesis of proteins.
  • Regulating cell membrane permeability.
  • Energy production through oxidative phosphorylation.

    • Which characteristic distinguishes non-membranous organelles from membranous organelles?

  • Presence of metabolic enzymes.
  • Absence of a surrounding membrane. (correct)
  • Involvement in energy production.
  • Ability to self-replicate.

    • How do mitochondria contribute to cellular energy production?

    <p>By producing ATP through oxidative phosphorylation.</p> Signup and view all the answers

    In what way do ribosomes and mitochondria differ functionally?

    <p>Ribosomes synthesize proteins, while mitochondria are responsible for ATP generation.</p> Signup and view all the answers

    What type of membrane structure is the cell membrane classified as?

    <p>Trilaminar membrane structure.</p> Signup and view all the answers

    Which component of the cytoskeleton is primarily involved in providing structural support?

    <p>Microfilaments.</p> Signup and view all the answers

    What is the primary function of microfilaments in cells?

    <p>Acting as a cytoskeleton</p> Signup and view all the answers

    In which form are carbohydrates stored in cells?

    <p>In the form of glycogen</p> Signup and view all the answers

    Which type of pigment is classified as endogenous?

    <p>Hemoglobin in red blood cells</p> Signup and view all the answers

    What type of structure do tonofibrils represent in epithelial cells?

    <p>Connection between adjacent cells</p> Signup and view all the answers

    How do microfilaments appear under a light microscope when stained?

    <p>As minute dots and fine lines</p> Signup and view all the answers

    Which statement correctly describes the function of the Rough Endoplasmic Reticulum?

    <p>Synthesis of proteins for secretion and hydrolytic enzymes.</p> Signup and view all the answers

    What microscopy characteristic distinguishes the Smooth Endoplasmic Reticulum from the Rough Endoplasmic Reticulum?

    <p>Formation of branching and anastomosing tubules.</p> Signup and view all the answers

    In which type of cells is the Rough Endoplasmic Reticulum most prevalent?

    <p>Cells responsible for protein secretion, such as pancreatic cells.</p> Signup and view all the answers

    Which of the following is NOT a function of the Golgi Apparatus?

    <p>Detoxification of drugs and chemicals.</p> Signup and view all the answers

    What is the significance of the 'negative Golgi image' observed in plasma cells?

    <p>It signifies an area characterized by diffuse basophilia.</p> Signup and view all the answers

    Which of the following statements best explains the structural appearance of the Rough Endoplasmic Reticulum under electron microscopy?

    <p>Contains parallel flattened membranous sacs with attached ribosomes.</p> Signup and view all the answers

    What type of substances can the Smooth Endoplasmic Reticulum assist in managing during muscle contractions?

    <p>Calcium ions for muscle contraction.</p> Signup and view all the answers

    Which of the following cells would contain a well-developed Smooth Endoplasmic Reticulum?

    <p>Adrenal cortex cells producing steroid hormones.</p> Signup and view all the answers

    What is the primary role of the Rough Endoplasmic Reticulum in relation to the Golgi apparatus?

    <p>To package and transport proteins to the Golgi apparatus.</p> Signup and view all the answers

    What is the primary role of lysosomal enzymes released during autolysis?

    <p>To hydrolyze cell constituents after cell death</p> Signup and view all the answers

    Which statement accurately describes ribosomes?

    <p>They can form polyribosomes by connecting multiple ribosomes with mRNA.</p> Signup and view all the answers

    In which form do ribosomes synthesize proteins used inside the cell?

    <p>As free ribosomes scattered throughout the cytoplasm</p> Signup and view all the answers

    What is the composition of microtubules?

    <p>Alpha and beta tubulin proteins arranged into protofilaments</p> Signup and view all the answers

    Which of the following is NOT a function of microtubules?

    <p>Initiating autolysis in dead cells</p> Signup and view all the answers

    How do attached ribosomes primarily function?

    <p>To synthesize proteins secreted as hormones or enzymes outside of cells</p> Signup and view all the answers

    What tissue observation indicates a high concentration of ribosomes?

    <p>Cytoplasmic basophilia, as seen in pancreatic cells</p> Signup and view all the answers

    Which statement best describes the structure of a ribosome?

    <p>Features a large subunit that houses the polypeptide chain</p> Signup and view all the answers

    Which of the following correctly describes the cytoskeleton?

    <p>A complex network of microtubules and microfilaments</p> Signup and view all the answers

    What is the primary function of secretory vesicles produced from the mature concave surface of the Golgi apparatus?

    <p>To bud off carrying protein ready for secretion.</p> Signup and view all the answers

    Which type of vesicle is formed when a primary lysosome fuses with a phagocytic vesicle containing bacteria?

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

    What role do transfer vesicles play in the function of Golgi apparatus?

    <p>They carry crude protein from the rough endoplasmic reticulum to the immature surface of Golgi.</p> Signup and view all the answers

    What typically differentiates primary lysosomes from secondary lysosomes in terms of appearance?

    <p>Primary lysosomes are homogeneous in electron density, while secondary lysosomes are heterogeneous.</p> Signup and view all the answers

    What is a residual body in the context of lysosomal function?

    <p>An undigested material that is expelled from the cell.</p> Signup and view all the answers

    Which of the following processes do lysosomes primarily contribute to?

    <p>Cellular digestion and waste removal.</p> Signup and view all the answers

    Which type of lysosome arises from the fusion of primary lysosomes with old organelles?

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

    Which statement best describes the origin of hydrolytic enzymes found in lysosomes?

    <p>They are synthesized in the rough endoplasmic reticulum and then transferred to the Golgi for packaging.</p> Signup and view all the answers

    What is the overall importance of the Golgi apparatus in protein processing?

    <p>It participates in the modification, sorting, and packaging of proteins for secretion.</p> Signup and view all the answers

    How do secondary lysosomes differ in internal composition compared to primary lysosomes?

    <p>Secondary lysosomes contain both digested and undigested materials.</p> Signup and view all the answers

    Study Notes

    Cell Organelles

    • Cells are living, permanent intracellular structures crucial for cell function.
    • Organelles are classified as membranous or non-membranous based on their membrane presence.

    Membranous Organelles

    • Enclosed by a membrane
    • Contain metabolic enzymes
    • Examples:
      • Cell membrane (plasma membrane/plasmalemma)
      • Mitochondria
      • Rough endoplasmic reticulum
      • Smooth endoplasmic reticulum
      • Golgi apparatus
      • Lysosomes

    Non-Membranous Organelles

    • Lack a surrounding membrane
    • Do not contain enzymes
    • Examples:
      • Ribosomes
      • Cytoskeleton (microtubules and microfilaments)

    The Cell Membrane

    • A thin membrane (7.5-10nm) surrounding the cell cytoplasm.
    • Not visible under light microscopy (LM).
    • Appears as a trilaminar membrane under electron microscopy (EM).
    • Consists of two dark lines separated by a clear line

    Mitochondria

    • Vital for energy production (the "powerhouse" of the cell)
    • Located in areas of high energy demand (e.g., muscle cells).
    • Appear as dark blue dots (LM) or green dots, using specific stains.
    • Have a double membrane structure (outer and inner).
    • Inner membrane folds (cristae) maximize surface area for energy production.
    • Contain DNA and RNA
    • Involved in ATP production via Krebs cycle and oxidative phosphorylation.

    Rough Endoplasmic Reticulum (rER)

    • Membrane-bound organelles involved in protein synthesis.
    • Located near the nucleus.
    • Appears as a network of flattened sacs (cisternae).
    • Studded with ribosomes (giving the rough appearance).
    • Involved in protein synthesis and processing for export out of the cell.

    Smooth Endoplasmic Reticulum (sER)

    • Membrane-bound system of tubules involved in steroid synthesis.
    • Abundant in steroid hormone-producing cells (e.g., adrenal cortex, testes).
    • Involved in detoxification, lipid synthesis, and calcium ion release.

    Golgi Apparatus

    • Involved in secretion (abundant in cells specializing in secretion).
    • Composed of flattened sacs (cisternae).
    • Processes, sorts, and packages proteins and lipids.

    Lysosomes

    • Membrane-bound organelles containing hydrolytic enzymes.
    • Responsible for cellular digestion.
    • Found in large numbers in phagocytic cells (e.g., macrophages, neutrophils).
    • Involved in breakdown of cellular debris and waste

    Ribosomes

    • Non-membranous organelles crucial for protein synthesis.
    • Composed of ribosomal RNA and proteins.
    • Appear as small granular structures (LM).
    • May be free-floating or bound to the rough endoplasmic reticulum (rER).

    Cytoskeleton

    • Network of microtubules and microfilaments.
    • Involved in cell shape maintenance and intracellular transport.
    • Essential for cell movement, division, and various cellular processes.

    Centrioles

    • Non-membranous organelles found near the nucleus.
    • Involved in cell division (mitosis).
    • Composed of microtubules

    Cilia and Flagella

    • Motile cellular extensions.
    • Composed of microtubules.
    • Involved in cell movement or transporting substances along cell surfaces.

    Cytoplasmic Inclusions

    • Non-living, nonessential components found in the cytoplasm.
    • Examples:
      • Stored food (carbohydrates, fats)
      • Pigments (endogenous/exogenous)
      • Secretory granules.

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