Biology Chapter 4: A Tour of the Cell
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Questions and Answers

What does cell theory state about living organisms?

  • All living things are made of cells and all cells arise from existing cells. (correct)
  • All living things are composed of tissues.
  • All cells are formed by spontaneous generation.
  • All cells can exist independently of other cells.
  • Which organism is known as the largest unicellular organism?

  • Valonia ventricosa
  • Caulerpa taxifolia (correct)
  • Amoeba proteus
  • Tardigrade
  • Which cellular component is found in both plant and animal cells?

  • Chloroplasts
  • Ribosomes (correct)
  • Lysosomes
  • Cell walls
  • What is the function of lysosomes in animal cells?

    <p>They digest macromolecules.</p> Signup and view all the answers

    Which of the following is NOT a feature common to all cells?

    <p>Organelles surrounded by membranes</p> Signup and view all the answers

    What is the main function of the nucleolus?

    <p>To produce components of ribosomes</p> Signup and view all the answers

    How do ribosomes in eukaryotic cells differ in their location?

    <p>Some are attached to the nuclear envelope and some are free in the cytosol</p> Signup and view all the answers

    What role does messenger RNA (mRNA) play in protein synthesis?

    <p>It carries DNA information to ribosomes for protein synthesis</p> Signup and view all the answers

    What structures allow the passage of materials between the nucleus and cytoplasm?

    <p>Nuclear pores</p> Signup and view all the answers

    What is formed when long DNA molecules and associated proteins combine?

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

    What happens to mRNA after it is synthesized in the nucleus?

    <p>It exits the nucleus through nuclear pores</p> Signup and view all the answers

    What determines the specific amino acid sequence of a protein?

    <p>The sequence of mRNA</p> Signup and view all the answers

    What are the dark blue dots seen in eukaryotic cells that represent ribosomes involved in protein synthesis?

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

    What is a primary function of smooth endoplasmic reticulum (SER) in liver cells?

    <p>Detoxification of lipid-soluble drugs</p> Signup and view all the answers

    How does smooth ER respond to an overload of ethanol from alcoholic drinking?

    <p>It doubles its surface area.</p> Signup and view all the answers

    What transformation do enzymes in the smooth ER facilitate for drugs and waste?

    <p>From lipid-soluble to water-soluble</p> Signup and view all the answers

    Which substance is specifically mentioned as being detoxified by smooth ER in liver cells?

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

    What occurs to the smooth ER's surface area once the detoxification demand decreases?

    <p>It returns to its normal size.</p> Signup and view all the answers

    Which type of drugs and substances are primarily processed by smooth ER enzymes for easier elimination?

    <p>Lipid-soluble drugs and metabolic wastes</p> Signup and view all the answers

    What happens to the smooth ER in response to a drug overdose?

    <p>It increases enzyme activity to manage the overload.</p> Signup and view all the answers

    What is the significance of the Golgi apparatus in relation to smooth ER?

    <p>It processes and modifies substances transported from rough ER.</p> Signup and view all the answers

    What is one of the primary functions of lysosomes in single-celled protists?

    <p>Fuse with food vacuoles to digest nutrients</p> Signup and view all the answers

    How do lysosomes contribute to the immune response in white blood cells?

    <p>By destroying harmful bacteria</p> Signup and view all the answers

    What happens to lysosomes in lysosomal storage diseases?

    <p>They become engorged with indigestible substances</p> Signup and view all the answers

    What role do lysosomes play during embryonic development?

    <p>They sculpt tissues by digesting structures</p> Signup and view all the answers

    What is a characteristic consequence of Tay-Sachs disease?

    <p>Accumulation of excess lipids in nerve cells</p> Signup and view all the answers

    What happens to small molecules resulting from digestion within lysosomes?

    <p>They nourish the cell by entering the cytoplasm</p> Signup and view all the answers

    What occurs when lysosomal digestive enzymes are not functioning properly?

    <p>The cells can become overloaded with waste</p> Signup and view all the answers

    Which of the following statements is true regarding lysosomes?

    <p>They help in recycling parts of damaged organelles</p> Signup and view all the answers

    What is the primary function of contractile vacuoles in freshwater protists like Paramecium?

    <p>To pump out excess water</p> Signup and view all the answers

    What role does the central vacuole play in plant cells?

    <p>It absorbs water contributing to cell expansion and growth</p> Signup and view all the answers

    What type of vacuole is formed as a vehicle for ingesting food particles from outside the cell?

    <p>Food vacuole</p> Signup and view all the answers

    In the context of vacuoles, what is a common characteristic of the environment surrounding freshwater protists?

    <p>It has lower solute concentration than the cell</p> Signup and view all the answers

    Which statement about the central vacuole in plant cells is incorrect?

    <p>It synthesizes proteins for the cell</p> Signup and view all the answers

    Which of the following is NOT a function of vacuoles in cells?

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

    How do contractile vacuoles maintain osmotic balance in protists?

    <p>By expelling excess water from the cell</p> Signup and view all the answers

    What accumulates in the central vacuole to enhance the growth of plant cells?

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

    Study Notes

    The Microscopic World of Cells

    • Cell theory: All living organisms are composed of cells; all cells arise from existing cells.
    • Every cell originates from the division of a previously existing cell.

    Notable Unicellular Organisms

    • Valonia ventricosa (Bubble algae): One of the largest known unicellular organisms.
    • Caulerpa taxifolia: The largest known single-celled organism, featuring one cell with multiple nuclei.

    Major Categories of Cells

    • All cells share common features: thin plasma membrane, cytosol, DNA chromosomes, and ribosomes.
    • Key differences:
      • Plant cells possess chloroplasts for photosynthesis.
      • Animal cells contain lysosomes for digestion.

    Nucleus and Ribosomes

    • The nucleolus: Site for ribosome component synthesis within the nucleus.
    • Ribosomes: Essential for protein synthesis, made in the nucleus and transported to the cytoplasm.
      • Two types:
        • Free ribosomes synthesize proteins within the cytosol.
        • Bound ribosomes (attached to rough ER) synthesize proteins for membranes or secretion.

    DNA and Protein Production

    • DNA transmits genetic information to messenger RNA (mRNA).
    • mRNA exits the nucleus through nuclear pores, binding to ribosomes to translate genetic codes into proteins.

    Endoplasmic Reticulum

    • Smooth ER: Functions in detoxifying substances (e.g., drugs, metabolic wastes); increases surface area in response to detoxification needs.
    • Rough ER: Studded with ribosomes; carries out protein synthesis and processing, transporting proteins to the Golgi apparatus.

    Golgi Apparatus

    • Functions as the receiving and processing center for proteins from the rough ER.
    • Transport vesicles carry proteins and enzymes to the Golgi for processing.

    Lysosomes

    • Contain digestive enzymes to break down food vacuoles and recycle organelle components.
    • Key functions:
      • Digestion of nutrients in protists.
      • Destruction of harmful bacteria.
      • Tissue sculpting during embryonic development.
    • Associated disorders: Lysosomal storage diseases lead to enzyme deficiencies causing accumulation of indigestible substances, often fatal in early childhood (e.g., Tay-Sachs disease due to lipid accumulation).

    Vacuoles

    • Membrane-bound sacs with varied functions in different cells:
      • Contractile vacuoles: Found in freshwater protists; regulate water balance by expelling excess water.
      • Central vacuole in plant cells: Occupies over half the cell volume; stores nutrients, absorbs water, aids growth, and contains pigments or poisons for protection.
      • Food vacuole: Engulfs food particles from the environment for nutrient uptake.

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