Endomembrane System in Eukaryotic Cells
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Questions and Answers

Which statement best describes the endomembrane system?

  • It is found only in prokaryotic cells.
  • It is present only in eukaryotic cells and is made up of compartments like the endoplasmic reticulum and Golgi apparatus. (correct)
  • It consists of cytoplasmic cavities bounded by membranes that do not intercommunicate.
  • It contains the nucleus and mitochondria.

    • Which organelle is linked to the nuclear envelope?

  • Endoplasmic reticulum (correct)
  • Golgi apparatus
  • Lysosomes
  • Phagosomes

    • What is the chemical composition of the endoplasmic reticulum?

  • It contains the plant vacuole.
  • It is not composed of membranes.
  • It is composed of rough microsomes.
  • It may be isolated from the 3rd pellet of the UCD in the form of rough or smooth microsomes. (correct)

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

    <p>Presence of ribosomes on the membrane</p> Signup and view all the answers

    What is the ultrastucture of ER membrane as seen in TEM?

    <p>Trilamellar and thinner than plasma membrane</p> Signup and view all the answers

    What is used to separate rough from smooth microsomes?

    <p>Centrifugation in a sucrose density gradient</p> Signup and view all the answers

    What type of fatty acids are present in the phospholipid bilayer of the smooth microsome membrane?

    <p>High percentage of unsaturated fatty acids</p> Signup and view all the answers

    What is the main purpose of centrifugation of the smooth microsomes in a sucrose concentration gradient?

    <p>To separate microsomes based on their density and origin</p> Signup and view all the answers

    What is the approximate protein content in the membrane of the smooth microsomes?

    <p>70%</p> Signup and view all the answers

    Where are carbohydrates found in relation to proteins and lipids in the smooth microsome membrane?

    <p>Towards the luminal surface</p> Signup and view all the answers

    What is the specific content of the cavity in the smooth endoplasmic reticulum (SER) dependent on?

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

    Where does protein synthesis for luminal proteins in the rough endoplasmic reticulum (RER) begin?

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

    What is the function of the signal sequence in protein synthesis for luminal proteins in the RER?

    <p>Enables the protein to be addressed for translocation</p> Signup and view all the answers

    What is the role of Signal Recognition Particle (SRP) in protein synthesis for luminal proteins in the RER?

    <p>Binds to the signal sequence and causes a temporary halt in translation</p> Signup and view all the answers

    What happens after the protein enters the lumen of the RER during protein synthesis for luminal proteins?

    <p>'The protein is taken up by chaperone proteins involved in translocation and post-translational modifications'</p> Signup and view all the answers

    What types of proteins can be synthesized in the rough endoplasmic reticulum (RER)?

    <p>Soluble or luminal proteins and hydrophobic proteins</p> Signup and view all the answers

    What represents 50 to 60% of the cell volume and is the fundamental substance of the cell in which organelles are immersed?

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

    What comprises a network of protein filaments and a complex aqueous solution within the cell?

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

    What is the pH range of hyaloplasm in plant cells?

    <p>pH 5.5 to 6</p> Signup and view all the answers

    In which cell part can hyaloplasm be found in the form of a gel or fluid?

    <p>Hyaloplasm itself</p> Signup and view all the answers

    Which part of the cell is specifically criss-crossed by fibrous or tubular structures contributing to its architecture and dynamics?

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

    Which organelle is linked to the nuclear envelope and plays a role in the architecture and dynamics of the cell?

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

    What is the main component of microtubules?

    <p>Globular protein of 50 kDa</p> Signup and view all the answers

    What is the diameter of the microtubules?

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

    What stabilizes the structure of microtubules?

    <p>Microtubule-associated proteins (MAPs)</p> Signup and view all the answers

    What are the permanent cellular elements made up of stable microtubules?

    <p>Centrioles and cilia/flagella</p> Signup and view all the answers

    What are centrioles composed of?

    <p>9 parallel triplets of short microtubules</p> Signup and view all the answers

    What are the characteristics of cilia and flagella?

    <p>Fine digitiform structures carried by the cell surface</p> Signup and view all the answers

    What types of microtubules are preserved regardless of the fixative and fixation temperature?

    <p>Stable microtubules</p> Signup and view all the answers

    What proteins are associated with the transport of vesicles along microtubules?

    <p>Kinesin and dynein</p> Signup and view all the answers

    What is the specific structure that makes up centrioles?

    <p>9 parallel triplets of short microtubules</p> Signup and view all the answers

    What is the diameter of the fine digitiform structures present in cilia and flagella?

    <p>0.25 μm</p> Signup and view all the answers

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