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Lesson 3 Cells, PPT

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  • What are the two broad types of cells?
    Prokaryotic and eukaryotic cells.
  • Where is DNA found in prokaryotic cells?
    DNA is found in the cytoplasm in a region called the nucleoid, which is not membrane-enclosed.
  • Where is DNA found in eukaryotic cells?
    DNA is enclosed within a nucleus surrounded by a double phospholipid membrane.
  • Which cell type has membrane-enclosed organelles?
    Eukaryotic cells have membrane-enclosed organelles; prokaryotic cells do not.
  • Do prokaryotic cells have histones for DNA packaging?
    No, prokaryotic cells do not have histones; eukaryotic cells do.
  • What is the significance of mitochondria and chloroplasts having their own circular DNA?
    It supports the endosymbiosis theory, suggesting these organelles originated from free-living prokaryotes.
  • Who proposed the endosymbiosis theory and when?
    Dr. Lynn Margulis first proposed it in the 1960s.
  • What is the goal of antibiotic research related to prokaryotes?
    To find compounds that kill bacteria without harming animal cells by targeting differences between prokaryotic and animal cells.
  • Which bacterial structure is the best target for antibiotics?
    The cell wall is a good antibiotic target because it is present in prokaryotes but absent in animal cells.
  • Are genome sizes proportional to organism complexity?
    No, genome size does not predict organism complexity.
  • Are the number of genes proportional to genome size?
    No, gene number is not proportional to genome size; humans have fewer genes per Mb than yeast.
  • How are genes organized differently in complex eukaryotes compared to prokaryotes?
    Complex eukaryotes have larger genes, more non-coding DNA, and genes spaced farther apart.
  • What is chromatin?
    In eukaryotes, DNA combined with histone proteins forms chromatin.
  • What is the typical path of a newly synthesized plasma membrane protein in a eukaryotic cell?
    Rough endoplasmic reticulum (RER) → Golgi apparatus → plasma membrane.
  • Where does protein translation occur in eukaryotic cells?
    On free ribosomes in the cytosol and on ribosomes attached to the rough endoplasmic reticulum.
  • How does a protein get targeted to the rough endoplasmic reticulum (RER)?
    By the presence of a signal peptide at the N-terminus of the growing polypeptide.
  • What role does the signal-recognition particle (SRP) play in protein targeting?
    SRP binds the signal peptide, pauses translation, and directs the ribosome to the ER membrane.
  • What happens to the signal peptide after the protein enters the ER?
    The signal peptide is cleaved off by an enzyme in the ER membrane complex.
  • What is cystic fibrosis caused by at the protein level?
    A defective CFTR protein that cannot be properly exported to the plasma membrane, impairing chloride ion transport.
  • How do CFTR modulators like Orkambi work?
    They help defective CFTR reach the membrane (Lumacaftor) and increase its activity once there (Ivacaftor).