Cell Biology: Endoplasmic Reticulum & Golgi Apparatus
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Questions and Answers

What is the main role of mitochondria in eukaryotic cells?

  • Photosynthesis in plant cells
  • Storage of genetic information
  • Generating ATP through cellular respiration (correct)
  • Digestion of cellular materials

    • Which of the following does NOT describe the structure of mitochondria?

  • Lacks internal compartments (correct)
  • Contains circular DNA
  • Surrounded by a double membrane
  • Has highly folded inner membrane called cristae

    • What is the function of peroxisomes in eukaryotic cells?

  • Break down fats and amino acids (correct)
  • Synthesize ATP from glucose
  • Store calcium ions
  • Rebuild damaged organelles

    • Which statement correctly describes the function of endosomes in eukaryotic cells?

    <p>They provide an environment for sorting internalized materials</p> Signup and view all the answers

    What is the primary function of ribosomes in a cell?

    <p>To translate the DNA genetic code into proteins</p> Signup and view all the answers

    What is produced as a by-product of metabolic reactions in peroxisomes?

    <p>Hydrogen peroxide (H2O2)</p> Signup and view all the answers

    What is the primary function of rough endoplasmic reticulum (rER)?

    <p>New membrane synthesis for the cell</p> Signup and view all the answers

    What do secretory vesicles transport to the cell membrane?

    <p>Molecules destined for secretion</p> Signup and view all the answers

    Which subunits compose Eukaryotic ribosomes?

    <p>60S and 40S</p> Signup and view all the answers

    Which type of digestion is primarily carried out by lysosomes?

    <p>Autophagy and recycling of cellular materials</p> Signup and view all the answers

    Where do free ribosomes primarily synthesize proteins for?

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

    Which of the following is NOT a function of smooth endoplasmic reticulum (sER)?

    <p>Modification of proteins</p> Signup and view all the answers

    What pH level do lysosomal enzymes work best at?

    <p>Acidic pH 4.5</p> Signup and view all the answers

    Which of the following describes the role of cytosol?

    <p>It is the aqueous component where organelles are suspended.</p> Signup and view all the answers

    How do transport vesicles utilize the Golgi apparatus?

    <p>They are modified on the cis side and expelled from the trans side.</p> Signup and view all the answers

    What is the main functional difference between free ribosomes and bound ribosomes?

    <p>Bound ribosomes produce proteins for secretion and membrane integration.</p> Signup and view all the answers

    What role do vacuoles play in plant cells?

    <p>They store nutrients and maintain turgor pressure.</p> Signup and view all the answers

    What components make up the cytoskeleton?

    <p>Microtubules, intermediate fibers, and microfilaments</p> Signup and view all the answers

    Which component is responsible for the detoxification of poisons in liver cells?

    <p>Smooth endoplasmic reticulum (sER)</p> Signup and view all the answers

    What is the role of secretory vesicles in a cell?

    <p>To transport and release substances outside the cell</p> Signup and view all the answers

    What is a key difference between vacuoles and vesicles?

    <p>Vacuoles are larger and have varied functions compared to vesicles.</p> Signup and view all the answers

    What primary function does the Golgi apparatus serve?

    <p>Modification and packaging of proteins</p> Signup and view all the answers

    What is one of the functionalities of the smooth endoplasmic reticulum (sER)?

    <p>Synthesis of steroid hormones</p> Signup and view all the answers

    Which organelles primarily use the cytoplasm for chemical activities in eukaryotic cells?

    <p>Ribosomes and lysosomes</p> Signup and view all the answers

    Study Notes

    Endoplasmic Reticulum (ER)

    • A series of interconnected channels and sacs called cisternae.
    • Two forms: Rough ER (rER) and Smooth ER (sER)
    • Rough ER (rER): Covered with ribosomes and synthesizes new membrane for the cell.
    • Smooth ER (sER): No ribosomes. Involved in:
      • Synthesis of membrane components like fatty acids and phospholipids
      • Synthesis of steroid hormones
      • Metabolism of carbohydrates
      • Detoxification of poisons, particularly in liver cells

    Golgi Apparatus

    • Composed of flattened, disk-like vesicles stacked together, located near the rER.
    • Plays a crucial role in modifying and packaging proteins made on ribosomes attached to the rER (bound ribosomes).
    • Transport vesicles fuse with one side of the Golgi and leave from the opposite side.
    • Sorts and modifies lipids and proteins as they move from the cis to the trans side.
    • Functions: Modify, sort, package, and manufacture/synthesize.
    • Often referred to as the "mail center" of the cell.

    Vacuoles

    • Space or cavity in the cytoplasm enclosed by a single membrane.
    • Larger than vesicles, can be derived from the ER and Golgi complex.
    • Specific functions vary depending on the cell type.
    • In plants:
      • Temporary storage organelles for proteins, nutrients, water, sugars, etc.
      • Store wastes and poisons to prevent toxicity to the cytoplasm (used for defense against predation).
      • Internal strength through turgor: Central vacuole takes up water, enabling plant cells to increase in size and provide rigidity to leaves and stems.
    • In animals: Involved in exocytosis and endocytosis (secretory, excretory & storage functions).

    Vesicles

    • Small membrane-enclosed transport units that transfer molecules between different cellular compartments.
    • Can fuse with other cell membranes.
    • Often referred to as "shuttle vehicles".

    Lysosomes

    • Membrane-enclosed spheres bound by a single membrane.
    • Contain about 40 different enzymes that work best in an acidic pH (4.5).
    • Function in the cell by:
      • Digesting other cells through phagocytosis.
      • Recycling cellular materials that have exceeded their lifespan and recycling cellular organic material through autophagy.

    Endosomes

    • Membrane-bound compartment inside eukaryotic cells.
    • Provide an environment for material taken into the cell by receptor-mediated endocytosis to be sorted before reaching the lysosome.

    Secretory Vesicles

    • Transport molecules to the cell membrane for secretion.

    Mitochondria

    • Sites of cellular respiration, a process that generates ATP (the energy molecule of the cell).
    • Found in all eukaryotic cells.
    • Approximately 1–10 µm long.
    • Structure:
      • Large organelles containing circular DNA.
      • Surrounded by a double membrane:
        • Inner membrane: Highly folded, folds are called cristae.
        • Outer membrane: Encloses the organelle.
    • These membranes divide the mitochondrion into two compartments:
      • Central matrix: Contains DNA in the form of a circular molecule.
      • Intermembrane space: Space between the inner and outer membranes.
    • Mitochondrial DNA: Encodes many of the components for mitochondrial function, while nuclear DNA encodes for the remaining components.

    Peroxisomes

    • Found in both plant and animal cells.
    • Break down fats and amino acids into smaller molecules that can be used for energy production by mitochondria.
    • Cytoplasmic vesicles where metabolic reactions occur that transfer hydrogen from various substrates to oxygen, producing hydrogen peroxide (H2O2) as a by-product.
    • H2O2 is highly reactive and toxic and is rapidly broken down by the enzyme catalase.

    Ribosomes

    • Translate the DNA genetic code into proteins.
    • Composed of RNA and protein.
    • Two subunits:
      • Eukaryotic ribosomes: 60S and 40S subunits that come together during protein synthesis to form an 80S ribosome.
      • Prokaryotic ribosomes: 50S and 30S subunit that come together during protein synthesis to form a 70S ribosome.
    • Occur in the cell either free in the cytoplasm or bound to the ER.
    • Bound ribosomes produce proteins destined for:
      • Plasma membrane
      • Nuclear membrane
      • Lysosomes
      • Golgi
      • Vacuoles
      • Secretory vesicles.
    • Free ribosomes synthesize proteins destined to be enzymes used in:
      • Cytoplasm (cytoplasmic enzymes)
      • Mitochondria
      • Chloroplasts.

    Cytoplasm

    • Region in eukaryotic cells between the cytoplasmic membrane and nuclear membrane.
    • Contains all the cell’s internal substructures (organelles) except the nucleus.
    • Liquid part: Cytosol.
    • Site of almost all the chemical activity occurring in a eukaryotic cell.

    Nucleoplasm

    • Similar to the cytoplasm of a cell.
    • Found inside the nucleus.

    Cytosol

    • Aqueous component of the cytoplasm of a cell.
    • Within which various organelles and particles are suspended.

    Cytoskeleton

    • Consists of:
      • Microtubules
      • Intermediate fibers
      • Microfilaments
    • Functions:
      • Maintaining cell shape
      • Anchoring organelles
      • Facilitating cell movement.

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    Lecture 1 Cell Structure PDF

    Description

    Explore the structure and functions of the Endoplasmic Reticulum and Golgi Apparatus in this quiz. Understand the differences between Rough and Smooth ER, their roles in cellular processes, and the critical functions of the Golgi Apparatus in protein packaging and modification.

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