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Questions and Answers

Which statement accurately reflects the contributions of Matthias Schleiden and Theodor Schwann?

  • Together, they formulated the foundations of cell theory. (correct)
  • Schwann stated that all plants consist of cells.
  • Schleiden proposed that all animals are made of cells.
  • They both discovered the existence of DNA.
  • What is the main difference between unicellular and multicellular organisms regarding reproduction?

  • Unicellular organisms reproduce through a process called mitosis.
  • Both types of organisms require a microscope to reproduce.
  • Multicellular organisms do not reproduce by cell division.
  • Unicellular organisms replicate by dividing; multicellular organisms grow through cell division. (correct)
  • According to the cell theory, which of the following statements is NOT true?

  • All cells are visible without the use of a microscope. (correct)
  • All living things are composed of cells.
  • Cells continuously reproduce themselves over generations.
  • Cells are the functional units of organisms.
  • What role do cells play in multicellular organisms?

    <p>Cells are both structural and functional units.</p> Signup and view all the answers

    Which of the following statements regarding the sizes of cells is accurate?

    <p>Amoeba proteus is a unicellular organism visible under a microscope.</p> Signup and view all the answers

    What is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells?

    <p>Prokaryotic cells lack a membrane-bounded nucleus.</p> Signup and view all the answers

    Which of the following is true about bacteria?

    <p>Bacteria typically measure between 1.1 to 1.5 micrometers wide.</p> Signup and view all the answers

    What is the role of ribosomes in prokaryotic cells?

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

    Which structure is found outside the plasma membrane of prokaryotic cells?

    <p>Cell wall</p> Signup and view all the answers

    Which of the following best describes eukaryotic cells?

    <p>They have a membrane-bounded nucleus and organelles.</p> Signup and view all the answers

    What is the function of the glycocalyx in bacterial cells?

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

    What distinguishes archaea from bacteria?

    <p>Archaea are often found in extreme environments.</p> Signup and view all the answers

    Which of the following is NOT a component of a typical bacterial cell?

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

    What is the primary function of cytosol in eukaryotic cells?

    <p>Central coordinating region for metabolic activities</p> Signup and view all the answers

    Which structural feature is common to both flagella and cilia?

    <p>They propagate movement through bending.</p> Signup and view all the answers

    What distinguishes smooth endoplasmic reticulum (SER) from rough endoplasmic reticulum (RER)?

    <p>SER is involved in detoxification, while RER synthesizes proteins.</p> Signup and view all the answers

    What is the main role of the Golgi apparatus in a eukaryotic cell?

    <p>Secretion, processing, and protein sorting</p> Signup and view all the answers

    Which organelles are considered semiautonomous?

    <p>Mitochondria and chloroplasts</p> Signup and view all the answers

    Which of the following statements about vacuoles is true?

    <p>Central vacuoles in plants aid in storage and structural support.</p> Signup and view all the answers

    What role does the nuclear envelope play in the cell?

    <p>It encloses the nucleus and has pores for material passage.</p> Signup and view all the answers

    Which component primarily aids in maintaining the shape of eukaryotic cells?

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

    How do lysosomes contribute to cellular function?

    <p>By breaking down macromolecules through hydrolysis</p> Signup and view all the answers

    What is unique about peroxisomes compared to other organelles?

    <p>They catalyze reactions to generate hydrogen peroxide.</p> Signup and view all the answers

    Which structure forms the outer boundary of a eukaryotic cell?

    <p>Plasma membrane</p> Signup and view all the answers

    What is a primary function of mitochondria in eukaryotic cells?

    <p>Energy production in the form of ATP</p> Signup and view all the answers

    What type of movement do actin filaments facilitate in the cytoskeleton?

    <p>Cellular contraction and shape changes</p> Signup and view all the answers

    How do vesicles communicate within the endomembrane system?

    <p>By transporting materials between organelles</p> Signup and view all the answers

    Study Notes

    The Cell

    • Matthias Schleiden, in the 1830s, stated that all plants are composed of cells.
    • Theodor Schwann stated that all animals are composed of cells.

    Organisms and Cells

    • Unicellular organisms are widespread.
    • Plants and animals, including humans, are multicellular.
    • The cell is the fundamental structural and functional building block of organisms; it is the smallest unit of life.

    Examples of Cells

    • Examples of cells: Amoeba Proteus, plant stem, bacteria, red blood cell, nerve cell.

    Cell Theory

    • Cells reproduce; when a cell reaches a certain size, it divides.
    • Unicellular organisms reproduce through cell division.
    • Multicellular organisms grow by cell division.
    • Cells play a role in the reproduction of multicellular organisms, ensuring cell continuity across generations.

    Cell Theory Statements

    • All living organisms are composed of one or more cells.
    • Cells are the smallest units of living organisms.
    • New cells arise only from pre-existing cells.

    Types of Cells

    • Two main cell types: prokaryotic and eukaryotic.

    Prokaryotic Cells

    • Prokaryotes lack a membrane-bound nucleus.
    • Prokaryotes are simpler and smaller than eukaryotes.
    • They are prevalent in air, water, soil, and even within human bodies.
    • Prokaryotes are divided into:
      • Bacteria: Abundant and mostly non-harmful.
      • Archaea: Less common, often found in extreme environments.

    Typical Bacterial Cell

    • Average size of bacteria is 1.1 to 1.5 micrometers in width and 2 to 6 micrometers in length
    • Bacteria are characterized by:
      • Plasma membrane: Acts as a barrier.
      • Cytoplasm: The interior region enclosed by the plasma membrane.
      • Nucleoid: Region containing genetic material (DNA).
      • Ribosomes: Involved in protein synthesis.
    • Structures outside of the plasma membrane:
      • Cell wall: Provides support and protection.
      • Glycocalyx: Traps water and offers protection.
      • Appendages:
        • Pili: For attachment.
        • Flagella: For locomotion.

    Eukaryotic Cells

    • Eukaryotic organisms include protists, fungi, plants, and animals.
    • Eukaryotes have a membrane-bound nucleus that houses DNA.
    • They are compartmentalized, containing specialized structures called organelles that perform specific functions.
    • Like prokaryotes, eukaryotes have a plasma membrane that separates the cell's contents from the environment and regulates passage of materials.
    • Shape, size, and organization of eukaryotic cells vary considerably across species and even among different cell types within a species.

    Cytosol

    • Cytosol is the region within a eukaryotic cell, outside of the organelles and inside the plasma membrane.
    • Cytoplasm encompasses everything within the plasma membrane, including cytosol, the endomembrane system, and semiautonomous organelles.
    • Cytosol is the central coordinating region for numerous metabolic activities in eukaryotic cells.
    • Metabolism includes:
      • Catabolism: Breakdown of molecules into smaller components.
      • Anabolism: Synthesis of cellular molecules and macromolecules.

    Cytoskeleton

    • Network of protein filaments extending from the nucleus to the plasma membrane in eukaryotic cells, maintaining cell shape and facilitating movement.
    • Three types of filaments:
      • Microtubules: Dynamic instability, organized at the centrosome (microtubule-organizing center) in animal cells.
      • Intermediate filaments: More stable than microtubules and actin filaments, with less dynamic polymerization and depolymerization.
      • Actin filaments: Also called microfilaments, involved in various cellular processes like cell movement.

    Flagella and Cilia

    • Flagella and cilia are involved in cell movement.
    • Flagella are typically longer than cilia and found singly or in pairs.
    • Cilia are generally shorter than flagella and cover part or all of a cell's surface.
    • Both structures share the same internal organization: microtubules, dynein, and axoneme.
    • Movement involves a bending wave, initiated at the base and progressing towards the tip.

    Endomembrane System

    • A network of membranes that enclose the nucleus, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
    • These structures cooperate and communicate through transport vesicles.
    • Plant cells lack lysosomes.

    Nuclear Envelope

    • Double-membrane structure surrounding the nucleus.
    • The outer membrane is continuous with the ER membrane.
    • Nuclear pores provide passageways for materials to enter and exit the nucleus.
    • The nucleus' contents are not part of the endomembrane system.

    Nucleus

    • Contains chromosomes, composed of DNA and protein (chromatin).
    • Primarily responsible for the protection, organization, and expression of the genetic material.
    • Ribosome assembly takes place in the nucleolus.

    Endoplasmic Reticulum (ER)

    • Intricate network of membranes forming flattened, fluid-filled tubules or cisternae.
    • The ER membrane encloses a single compartment called the ER lumen.
    • Types:
      • Rough endoplasmic reticulum (rough ER): Studded with ribosomes, involved in protein synthesis and sorting.
      • Smooth endoplasmic reticulum (smooth ER): Lacks ribosomes, involved in detoxification, carbohydrate metabolism, calcium balance, and synthesis/modification of lipids.

    Golgi Apparatus

    • Also known as the Golgi body, Golgi complex, or simply Golgi.
    • Stack of flattened, membrane-bound compartments, not continuous with the ER.
    • Vesicles facilitate transport of materials between stacks.
    • Functions:
      • Secretion
      • Processing
      • Protein sorting

    Lysosomes

    • Contain acid hydrolases, enzymes that catalyze hydrolysis.
    • Possess various acid hydrolases to break down proteins, carbohydrates, nucleic acids, and lipids.
    • Autophagy involves the recycling of worn-out organelles through endocytosis.

    Vacuoles

    • Vacuole functions vary widely across cell types and environmental conditions.
    • Types:
      • Central vacuoles in plants: Storage and support.
      • Contractile vacuoles in protists: Expelling excess water.
      • Phagocytic vacuoles in protists and white blood cells: Degradation.

    Plasma Membrane

    • Boundary between the cell and the extracellular environment.
    • Controls the passage of materials into and out of the cell (selectively permeable).
    • Cell signaling through receptors.
    • Cell adhesion.

    Semiautonomous Organelles

    • Can grow and divide to reproduce themselves but are not entirely independent.
    • Require other cellular components for their internal structures.
    • Examples:
      • Mitochondria
      • Chloroplasts
      • Peroxisomes

    Mitochondria

    • Possess outer and inner membranes, creating an intermembrane space and a mitochondrial matrix.
    • Primary function is to produce energy in the form of ATP.
    • Also involved in the synthesis, modification, and breakdown of various cellular molecules.
    • Can generate heat in brown fat cells.

    Chloroplasts

    • Responsible for photosynthesis: capturing light energy and using it to synthesize organic molecules like glucose.
    • Found in nearly all plants and algae.
    • Have outer and inner membranes with an intermembrane space.
    • Third membrane, the thylakoid membrane, forms flattened tubules that stack into a granum (plural, grana).

    Peroxisomes

    • Small organelles present in all eukaryotic cells.
    • Catalyze certain chemical reactions, typically involving the breakdown of molecules by removing hydrogen or adding oxygen.
    • Reactions produce hydrogen peroxide (H2O2).
    • Catalase in peroxisomes breaks down H2O2 without generating harmful free radicals.

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