Week 3: The Cell Structure and Organelles
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Week 3: The Cell Structure and Organelles

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Questions and Answers

What is the primary function of the pore complex found in the nuclear envelope?

  • Regulating the entry and exit of proteins and RNAs (correct)
  • Initiating DNA replication
  • Coiling the DNA molecule
  • Synthesizing ribosomal RNA

    • Which structure is responsible for maintaining the nuclear envelope's shape?

  • Ribosomes
  • Nuclear lamina (correct)
  • Nucleolus
  • Chromatin

    • Which statement about chromatin is accurate?

  • Chromatin is formed exclusively from RNA.
  • Heterochromatin is less condensed than euchromatin.
  • Euchromatin is where most transcribed genes are located. (correct)
  • All chromatin is uniformly distributed within the nucleus.

    • In human cells, how many chromosomes are typically found in the nucleus?

    <p>46 chromosomes in somatic cells only</p> Signup and view all the answers

    What distinguishes heterochromatin from euchromatin?

    <p>Heterochromatin is less accessible for transcription.</p> Signup and view all the answers

    Where in the nucleus is ribosomal RNA synthesized?

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

    What is the average diameter of the pores in the nuclear envelope?

    <p>100 nm</p> Signup and view all the answers

    What type of chromatin appears as clumps of densely staining material?

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

    What is the primary role of microtubules in animal cells?

    <p>They function as compression-resisting girders of the cytoskeleton.</p> Signup and view all the answers

    Why are centrioles considered important before cell division in animal cells?

    <p>They replicate and assist in organizing microtubules.</p> Signup and view all the answers

    What distinguishes the 'plus end' of a microtubule?

    <p>It shows a higher rate of accumulating and releasing tubulin dimers.</p> Signup and view all the answers

    Which of the following statements about centrosomes is true?

    <p>Centrosomes are microtubule-organizing centers located near the nucleus in animal cells.</p> Signup and view all the answers

    What structural arrangement is found within each centriole?

    <p>Nine sets of triplet microtubules arranged in a ring.</p> Signup and view all the answers

    Which of the following correctly describes a function of the Rough Endoplasmic Reticulum?

    <p>Production of secretory proteins and glycoproteins</p> Signup and view all the answers

    What role does the Smooth Endoplasmic Reticulum play in muscle cells?

    <p>It stores calcium ions that trigger muscle contraction</p> Signup and view all the answers

    What is a consequence of the proliferation of Smooth Endoplasmic Reticulum in response to drug metabolism?

    <p>Increased tolerance to drugs</p> Signup and view all the answers

    Which of the following statements about the Smooth Endoplasmic Reticulum is accurate?

    <p>It detoxifies various drugs by adding hydroxyl groups</p> Signup and view all the answers

    What type of proteins are primarily produced by the Rough Endoplasmic Reticulum?

    <p>Secretory and glycoproteins</p> Signup and view all the answers

    Which cellular structure is continuous with the Endoplasmic Reticulum?

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

    Which of the following functions is NOT associated with the Smooth Endoplasmic Reticulum?

    <p>Production of ATP</p> Signup and view all the answers

    What impact do barbiturates have on the Smooth Endoplasmic Reticulum in liver cells?

    <p>They induce the proliferation of Smooth ER</p> Signup and view all the answers

    The presence of ribosomes on the Rough Endoplasmic Reticulum enables it to primarily synthesize what type of proteins?

    <p>Membrane-bound proteins</p> Signup and view all the answers

    Which steroid hormones are synthesized in cells rich in Smooth Endoplasmic Reticulum?

    <p>Sex hormones and steroid hormones secreted by adrenal glands</p> Signup and view all the answers

    What is a primary function of peroxisomes in metabolic processes?

    <p>Conversion of hydrogen peroxide to water</p> Signup and view all the answers

    Which genetic defect is associated with Zellweger syndrome?

    <p>Mutations in PEX genes</p> Signup and view all the answers

    What is the first symptom commonly associated with MERRF syndrome?

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

    What role do peroxisomes play in liver function?

    <p>Detoxifying alcohol and harmful compounds</p> Signup and view all the answers

    Which aspect of mitochondria is highlighted in the description of their autonomy?

    <p>Their capacity to grow and reproduce within the cell</p> Signup and view all the answers

    What is a result of dysfunctional lipid metabolism in Zellweger spectrum disorders?

    <p>Over-accumulation of very long-chain fatty acids</p> Signup and view all the answers

    What cellular function do chloroplasts share with mitochondria?

    <p>Energy production</p> Signup and view all the answers

    What are ragged red fibers indicative of in muscle biopsy results?

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

    In what way do mitochondria and chloroplasts show independence from the cell?

    <p>They can synthesize some of their own proteins.</p> Signup and view all the answers

    Which of the following statements characterizes peroxisomes?

    <p>They are involved in the breakdown of fatty acids.</p> Signup and view all the answers

    What is the primary function of the Golgi apparatus?

    <p>Manufacturing macromolecules and packaging materials</p> Signup and view all the answers

    What effect does the acidic environment within lysosomes have on lysosomal enzymes?

    <p>It activates the enzymes for optimum digestion</p> Signup and view all the answers

    What is the process called when lysosomes recycle the cell’s own organelles?

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

    Which of the following accurately describes the cis and trans faces of the Golgi apparatus?

    <p>The cis face is the receiving side, while the trans face is the shipping side.</p> Signup and view all the answers

    What are lysosomal storage diseases primarily caused by?

    <p>Defective lysosomal function</p> Signup and view all the answers

    What happens when a lysosome leaks its contents into the cytoplasm?

    <p>The enzymes begin digesting cellular components.</p> Signup and view all the answers

    Which of the following macromolecules can lysosomal enzymes hydrolyze?

    <p>All types of macromolecules: proteins, fats, polysaccharides, and nucleic acids</p> Signup and view all the answers

    What term is used to describe the process by which a cell engulfs another cell to form a food vacuole?

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

    How do molecular identification tags function in the Golgi apparatus?

    <p>They serve as postal addresses for sorting and packaging materials.</p> Signup and view all the answers

    Which of the following statements is true regarding macrophages?

    <p>They help defend the body by engulfing and destroying bacteria.</p> Signup and view all the answers

    Study Notes

    Nuclear Envelope

    • The nuclear envelope is perforated by pore structures that are about 100 nm in diameter.
    • The inner and outer membranes of the nuclear envelope are continuous at the lip of each pore.
    • An intricate protein structure called a pore complex lines each pore and plays a role in regulating the entry and exit of proteins and RNAs, and large complexes of macromolecules.
    • The nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus.

    Chromatin

    • The genetic material in the nucleus is called chromatin.
    • DNA and proteins form chromatin.
    • Chromatin condenses to form chromosomes.
    • Some proteins help coil the DNA in each chromosome, reducing the length and allowing it to fit into the nucleus.
    • Histones are the name of these proteins.
    • A typical human cell has 46 chromosomes in its nucleus.
    • Exceptions are the sex cells (eggs and sperm), which have only 23 chromosomes in humans.

    Heterochromatin vs. Euchromatin

    • Chromatin does not have a homogeneous appearance in most cells.
    • Clumps of densely staining chromatin can be found in a more lightly staining background.
    • The densely staining material is called heterochromatin and the lightly staining material is called euchromatin.

    Nucleolus

    • The nucleolus is a small area within the nucleus.
    • The nucleolus is a site of rRNA synthesis.
    • The nucleolus contains DNA in the form of rRNA genes, RNA and proteins.
    • The nucleolus contains regulatory cell cycle proteins.

    Endoplasmic Reticulum

    • The ER membrane is continuous with the nuclear envelope.
    • The ER is divided into two distinct regions: rough ER and smooth ER.

    Rough ER

    • Rough ER has bound ribosomes, which produce secretory proteins.
    • Secretory proteins are mostly glycoproteins, or proteins bonded with carbohydrates.
    • Rough ER distributes transport vesicles.
    • The rough ER is a membrane factory for the cell.

    Smooth ER

    • Smooth ER synthesizes lipids.
    • Smooth ER metabolizes carbohydrates.
    • Smooth ER stores calcium.
    • The smooth ER detoxifies poisons and drugs.

    Golgi Apparatus

    • The Golgi apparatus consists of flattened membranous sacs called cisternae.
    • The Golgi apparatus modifies, stores and sends products from the ER.
    • The Golgi apparatus manufactures certain macromolecules.
    • The Golgi apparatus sorts and packages materials into transport vesicles.
    • The Golgi apparatus adds molecular identification tags as address in mailing labels.

    Lysosome

    • Lysosomes are membranous sacs containing hydrolytic enzymes.
    • Lysosomes digest macromolecules.
    • Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids.
    • Lysosomal enzymes work best in the acidic environment of lysosomes.

    Mitochondria

    • Mitochondria are autonomous organelles that grow and reproduce within the cell.
    • Mitochondria have their own DNA.

    Peroxisomes

    • Peroxisomes are specialized metabolic compartments.
    • Peroxisomes produce hydrogen peroxide and convert it to water.
    • Peroxisomes contain enzymes that break down fatty acids.
    • Peroxisomes in the liver detoxify alcohol and other harmful compounds.

    Centrosome – Centrioles

    • In animal cells, microtubules grow out from a centrosome, a region near the nucleus considered a “microtubule-organizing center.”
    • Centrosomes function as compression-resisting girders.
    • Before an animal cell divides, the centrioles replicate.
    • Each centriole is composed of nine sets of triplet microtubules arranged in a ring.
    • Centrioles are not essential for microtubule assembly in all eukaryotes (not present in fungi and plant cells).

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    The Cell & Organelles PDF

    Description

    Explore the structures and functions of the nuclear envelope and chromatin in this quiz. Understand the role of pore complexes, the composition of chromatin, and how DNA is organized within the nucleus. Test your knowledge on these fundamental concepts in cell biology.

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