Biology Chapter 5: Cell Morphology
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Questions and Answers

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

  • Eukaryotic cells possess an enclosed nucleus. (correct)
  • Eukaryotic cells do not undergo transcription.
  • Eukaryotic cells lack membrane bound organelles.
  • Eukaryotic cells have a rigid cell wall.

    • What process describes the conversion of genetic information from DNA to messenger RNA?

  • Replication
  • Transcription (correct)
  • Translation
  • Transduction

    • Which of the following terms refers to the observable characteristics of an organism?

  • Genotype
  • Chromatin
  • Phenotype (correct)
  • Allele

    • What are ribosomes primarily responsible for in a cell?

    <p>Translation of RNA into protein</p> Signup and view all the answers

    Which statement regarding chitin is true?

    <p>Chitin is a complex carbohydrate found in fungi cell walls.</p> Signup and view all the answers

    What describes the 'blastula' stage in animals?

    <p>A hollow sphere of cells during embryonic development.</p> Signup and view all the answers

    What is the role of histones in relation to DNA?

    <p>They wrap around DNA to form chromatin.</p> Signup and view all the answers

    Which type of cells are genetically more similar to animals than to plants?

    <p>Fungi cells</p> Signup and view all the answers

    What is the primary function of tRNA in protein synthesis?

    <p>To transport amino acids to the ribosome</p> Signup and view all the answers

    What distinguishes membrane-bound ribosomes from free ribosomes?

    <p>Membrane-bound ribosomes are attached to the endoplasmic reticulum</p> Signup and view all the answers

    What is the role of the Golgi apparatus in the cell?

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

    What occurs during constitutive secretion?

    <p>Vesicles continuously transport proteins to the plasma membrane</p> Signup and view all the answers

    What is a key feature of regulated secretion?

    <p>Proteins are stored in vesicles until a specific signal is triggered</p> Signup and view all the answers

    How does the smooth endoplasmic reticulum (SER) differ from the rough endoplasmic reticulum (RER)?

    <p>SER is involved in lipid and steroid synthesis with fewer ribosomes</p> Signup and view all the answers

    What describes the function of cisternae in the Golgi apparatus?

    <p>They help in processing and transporting proteins</p> Signup and view all the answers

    What molecules are typically released through exocytosis?

    <p>Hormones, enzymes, and other signaling molecules</p> Signup and view all the answers

    What is the primary function of kinesin in the cell?

    <p>Moving organelles and vesicles away from the nucleus</p> Signup and view all the answers

    Which compartment is located inside the inner membrane of mitochondria?

    <p>Mitochondrial matrix</p> Signup and view all the answers

    What do cristae in mitochondria primarily enhance?

    <p>ATP production surface area</p> Signup and view all the answers

    Which type of junction allows for chemical communication between neighboring cells?

    <p>Gap junctions</p> Signup and view all the answers

    In chloroplasts, what pigment is primarily responsible for synthesizing ATP?

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

    What is the role of tight junctions in epithelial cells?

    <p>Control water and solute movement</p> Signup and view all the answers

    During which process do mitochondria divide?

    <p>Binary fission</p> Signup and view all the answers

    Which of the following is NOT a component of adherens junctions?

    <p>Desmosome proteins</p> Signup and view all the answers

    What is the primary function of lysosomes in a cell?

    <p>Destroying proteins using digestive enzymes</p> Signup and view all the answers

    What are actin filaments primarily responsible for in eukaryotic cells?

    <p>Changing the cell's shape and facilitating movement</p> Signup and view all the answers

    What distinguishes a lysozyme from a lysosome?

    <p>A lysozyme is an enzyme that functions within a lysosome.</p> Signup and view all the answers

    Which cytoskeletal element helps in moving organelles and vesicles within the cell?

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

    What process is primarily facilitated by actin filaments during cell division?

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

    What role do motor proteins like kinesin and dynein play in relation to microtubules?

    <p>They transport cargo along microtubules towards their respective destinations.</p> Signup and view all the answers

    What is the diameter of microtubules?

    <p>25 nm</p> Signup and view all the answers

    Which statement about pseudopodia is true?

    <p>They are temporary protrusions for movement and/or feeding.</p> Signup and view all the answers

    Study Notes

    Morphology

    • External morphology refers to an organism's size, shape, color, pattern, and outward appearance.
    • E. coli and S. cerevisiae are Latin names and should be italicized.

    Prokaryotic cells

    • Lack an enclosed nucleus or membrane-bound organelles.
    • Examples include cocci, bacilli, and vibrio.

    Eukaryotic cells

    • Include plants, animals, and fungi.
    • Possess a nucleus enclosed in an envelope and membrane-bound organelles.

    Plant cells

    • Most plants are multicellular organisms.
    • Obtain energy through photosynthesis.

    Fungi cells

    • Include yeasts, molds, and mushrooms.
    • Heterotrophs with chitin in their cell walls.
    • Genetically more similar to animals than plants.
    • Heterotrophic organisms consume other plants or animals for energy and nutrients.
    • Chitin is a polysaccharide chain.

    Animal cells

    • Heterotrophic, motile or non-motile.
    • Have a blastula stage of embryonic development.
    • A blastula is a hollow sphere of cells.
    • Eukaryotic cells can be rigid like calcified bone, fluid and flexible like neutrophils, or brick-shaped and fixed like columnar epithelial cells.

    Organelles

    • Eukaryotes have numerous membrane-bound organelles, while prokaryotes have none.

    Nucleus

    • The nucleus has entry and exit points called nuclear pores.
    • Chromatin is a complex of DNA and protein, where DNA wraps around histones.

    Genes to Proteins

    • The central dogma describes how genetic information is stored in DNA and converted into a product (protein) within a biological system.
    • Transcription: DNA → messenger RNA (mRNA)
    • Translation: mRNA → protein
    • There are only 4 nucleotides but 20 amino acids, representing a transition from the language of DNA to the language of protein.
    • Genotype: the genes an organism possesses.
    • Phenotype: the observable characteristics of an organism.

    Translation

    • Requires 4 nucleotides to translate from mRNA to protein, but there are 20 amino acids.
    • More complicated than going from DNA to RNA.
    • No equivalent of Watson-Crick base pairing.

    Ribosomes

    • Molecular machines that help cells make proteins.
    • Composed of two parts:
      • Small subunit: Reads mRNA instructions for adding amino acids to the growing protein.
      • Large subunit: Links amino acids together, forming peptide bonds.
    • Amino acids are brought to the ribosome by tRNA.

    Types of Ribosomes

    • Free ribosomes float freely in the cytosol and can work together in groups called polysomes to make proteins. All ribosomes in bacteria (prokaryotes) are free-floating.
    • Membrane-bound ribosomes are attached to the surface of the endoplasmic reticulum (ER) in eukaryotic cells and help make proteins that are sent to specific places.

    Endoplasmic Reticulum (ER)

    • Rough ER (RER): Has ribosomes attached and helps make proteins that are sent to specific places.
    • Smooth ER (SER): Has fewer ribosomes, smaller size, and is involved in lipid, phospholipid, and steroid synthesis.

    Golgi Body

    • Also known as Golgi apparatus, Golgi complex, or Golgi.
    • Cisternae are flat stacks found in certain cell structures like ER or Golgi.
    • Involved in processing and transport of proteins and other molecules.
    • Proteins arrive from the ER at the cis face and are modified within the cisternae by enzymes.
    • Proteins are sorted in the trans Golgi network and sent to the following locations:
      • Cell membrane for secretion
      • Lysosomes for digestion

    Protein Sorting

    • The trans Golgi network (TGN) packages proteins into small membrane-bound vesicles for transport.
    • Constitutive/exocytotic secretion: Vesicles continuously transport proteins to the plasma membrane, releasing materials like lipids, proteins, and secretory proteins outside the cell.
    • Regulated Secretion: Proteins are stored in vesicles until a specific signal triggers their release.

    Lysosomes

    • Digestive enzymes (lysozymes) are synthesized in the rough endoplasmic reticulum (RER).
    • Lysosomes are vesicles containing lysozymes.
    • Lysosomes are involved in digesting proteins, waste materials, and harmful substances like bacteria.
    • Lysosomal exocytosis can either send proteins to the lysosome for destruction or send lysozymes to digest something outside the cell.

    How things move inside the cell

    • nm: nanometer (1 millimeter = 1,000 micrometers = 1,000,000 nanometers).
    • Pseudopodia: temporary protrusions of the cell's surface for movement and/or feeding.

    Cytoskeletal elements

    • Protein-based structures within cells that provide support, shape, and organization.
    • Involved in movement, division, and maintaining cell integrity.
    • Three main types:
      • Microtubules
      • Intermediate filaments
      • Microfilaments

    Microtubules

    • Made from tubulin, hollow tubes with a diameter of 25 nm.
    • Help move organelles and vesicles inside the cell.
    • Motor proteins (kinesin and dynein) attach to the outside of the microtubule and transport cargo.
    • Kinesin moves towards the cell's edge (positive end), while dynein moves towards the nucleus (negative end).
    • Cargo refers to materials like organelles, vesicles, proteins, and other cellular components.

    Mitochondria

    • Bacilli-shaped, divide by binary fission.
    • Produce ATP (energy).
    • Have two membranes with an intermembrane space.
    • The inner membrane forms cristae, dividing the mitochondrion into two compartments:
      • Intermembrane space
      • Mitochondrial matrix
    • Cristae increase the surface area of the inner membrane, improving the mitochondrion's ability to produce ATP.
    • Mitochondria contain their own DNA, separate from the cell's main DNA.

    Chloroplast

    • Bacilli-shaped, divide by binary fission.
    • Synthesize ATP through a photosynthetic pigment called chlorophyll.
    • Have two membranes with an intermembrane space.
    • Contain their own DNA, separate from the rest of the cell's DNA.

    Cell Junctions

    • Help hold cells together and allow communication between neighboring cells.
    • Permit movement of water and solutes between cells (osmotic regulation).

    Gap Junctions

    • Facilitate chemical communication between cells.
    • Formed by a connexon cylinder consisting of six connexin proteins.
    • Allow the movement of smaller structures within cells due to a very small gap between the cells.

    Adherens and Desmosomes

    • Anchor cells to one another.
    • Adherens junctions connect cells via actin-to-actin links through cadherin or integrins.
    • Desmosomes connect cells via keratin-to-keratin links through cadherin.
    • Hemidesmosomes connect the cytoskeleton of cells to the extracellular matrix via integrins.

    Tight Junctions

    • Control water and solute movement between epithelial cells.
    • Line organs and blood vessels.
    • Tighter junctions create tighter barriers, while fewer tight junctions result in leakier barriers.

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