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What is the primary function of intermediate filaments in animal cells?

  • To produce ATP for cellular functions
  • To assist in cell division
  • To provide support for cells and tissues (correct)
  • To facilitate nutrient transport across cell membranes

    • Which step in the assembly of intermediate filaments involves the formation of a non-polar tetramer?

  • Formation of coiled-coil dimers
  • Joining of 8 tetramers
  • Staggering of two dimers (correct)
  • Addition of polypeptides to filament

    • Which type of protein forms the intermediate filaments in epithelial cells?

  • Neurofilaments
  • Lamin
  • Vimentin
  • Keratin (correct)

    • What structure serves as the primary site for microtubule assembly in non-dividing cells?

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

    Which protein is crucial for correctly orienting the alpha and beta dimers during microtubule assembly?

    <p>Gamma tubulin</p> Signup and view all the answers

    What occurs if intermediate filaments in epithelial cells are disrupted?

    <p>Skin begins to blister</p> Signup and view all the answers

    What type of filament assembly occurs when 8 tetramers come together?

    <p>Creation of a diameter structure</p> Signup and view all the answers

    Which intermediate filament is associated with nuclear structure in animal cells?

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

    What process regulates the growth and shrinkage of microtubules?

    <p>Dynamic instability</p> Signup and view all the answers

    What is the effect of the GTP cap on microtubule dynamics?

    <p>It encourages growth by stabilizing dimers.</p> Signup and view all the answers

    Which domain of actin is associated with ATP binding?

    <p>Barbed end</p> Signup and view all the answers

    Which protein is involved in promoting the exchange of actin-ADP to actin-ATP?

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

    What is the main phenomenon that describes the addition and loss of actin subunits in microfilaments?

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

    What happens when the concentration of GTP dimers is low in a microtubule?

    <p>The GTP cap is lost, causing disassembly.</p> Signup and view all the answers

    What is the primary role of the myosin motor protein during cell movement?

    <p>To contract the cell by pushing actin filaments closer together</p> Signup and view all the answers

    Which of the following functions is NOT associated with actin filaments?

    <p>Transport of organelles</p> Signup and view all the answers

    Which process is involved in the glycosylation of proteins in the ER?

    <p>Addition of carbohydrate sequences</p> Signup and view all the answers

    What is the role of MAP proteins in relation to microtubules?

    <p>Stabilize microtubules and prevent disassembly.</p> Signup and view all the answers

    Which type of protein is needed for vesicle formation of soluble ER proteins?

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

    What triggers the unfolded protein response (UPR) in a cell?

    <p>Too many abnormally folded or unfolded proteins</p> Signup and view all the answers

    What modification occurs only in the lumen of the endoplasmic reticulum?

    <p>Formation of disulfide bonds</p> Signup and view all the answers

    Which organelle is primarily responsible for degrading macromolecules within a cell?

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

    What is the function of ARP ⅔ in cell movement?

    <p>To initiate actin polymerization</p> Signup and view all the answers

    How do membrane proteins differ when being transported from the ER to the Golgi?

    <p>They require a receptor to assist in vesicle formation</p> Signup and view all the answers

    What is the role of coat proteins in vesicular transport?

    <p>To bind cargo and cause the membrane to pucker for vesicle formation.</p> Signup and view all the answers

    Which type of coat protein is required for transporting proteins from the ER to the Golgi?

    <p>COP II</p> Signup and view all the answers

    What is the function of dynamin in vesicular transport?

    <p>To pinch off vesicles from the membrane using ATP.</p> Signup and view all the answers

    How do vesicles recognize the correct target membrane?

    <p>Through the interaction of Rab proteins and tethering proteins.</p> Signup and view all the answers

    What sequence do ER resident proteins have that allows COP I to transport them back to the ER?

    <p>KDEL sequence</p> Signup and view all the answers

    What happens to coat proteins after vesicle budding occurs?

    <p>They are removed, making receptors accessible.</p> Signup and view all the answers

    Which motor protein is most commonly involved in transporting vesicles to their destination?

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

    What occurs during the fusion of a vesicle with the target membrane?

    <p>Water is expelled and the membranes interconnect through V-snares and T-snares.</p> Signup and view all the answers

    What characterizes constitutive secretion?

    <p>Occurs in an unregulated manner</p> Signup and view all the answers

    What is the first step in receptor-mediated endocytosis?

    <p>Cargo binds to the LDL receptor</p> Signup and view all the answers

    Which cell signaling type involves hormones traveling through the bloodstream?

    <p>Endocrine signaling</p> Signup and view all the answers

    Where are receptors for lipid-soluble signaling molecules typically located?

    <p>Inside the cytoplasm</p> Signup and view all the answers

    Which of the following is a function of G proteins in signaling pathways?

    <p>Hydrolyze GTP or exchange GDP to GTP</p> Signup and view all the answers

    What effect does phosphorylation have in signaling pathways?

    <p>Alters the shape of proteins to enable signaling</p> Signup and view all the answers

    What is a potential outcome of altering protein synthesis in cells?

    <p>Cell survival or death</p> Signup and view all the answers

    How do secondary messengers function in cellular signaling?

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

    What is the primary characteristic of paracrine signaling?

    <p>Signals operate in a localized area</p> Signup and view all the answers

    Which type of signaling is characterized by membrane-bound signals that require direct contact with the target cell?

    <p>Contact-dependent signaling</p> Signup and view all the answers

    What is the primary role of PKA in relation to glycogen synthase?

    <p>To inactivate glycogen synthase, preventing glycogen formation</p> Signup and view all the answers

    Which mechanism is responsible for the inactivation of G-proteins?

    <p>Removal of the signaling molecule and GTP hydrolysis</p> Signup and view all the answers

    What is the function of Pi3K in the RTK-AKT signaling pathway?

    <p>To convert PIP2 to PIP3</p> Signup and view all the answers

    What occurs after AKT is activated in the RTK-AKT pathway upon insulin binding?

    <p>AKT facilitates the insertion of glucose transporters into the plasma membrane</p> Signup and view all the answers

    What is the consequence of AKT phosphorylating PP1?

    <p>It deactivates phosphorylase kinase and glycogen phosphorylase, preventing glycogen breakdown</p> Signup and view all the answers

    What structural feature do RTKs exhibit when they bind signaling molecules?

    <p>They dimerize and cross-phosphorylate each other</p> Signup and view all the answers

    What effect does the signaling molecule insulin have in the RTK-AKT pathway?

    <p>It activates glucose transporters to reduce blood glucose levels</p> Signup and view all the answers

    What type of receptor is involved in the activation of AKT?

    <p>Receptor tyrosine kinase (RTK)</p> Signup and view all the answers

    Study Notes

    Introduction to Cell Biology Exam #4

    • This exam covers material from Miami University's BIO 203 course.
    • It focuses on cell biology topics such as intermediate filaments, microtubules, dynamic instability, and the transport mechanisms involving proteins.

    Intermediate Filaments

    • Found only in animal cells
    • Provide structural support to cells and tissues
    • Composed of many polypeptide chains
    • Assembly involves forming dimers, then tetramers, ultimately into stable filaments
    • Different types exist in different cell types (e.g., keratin in epithelial cells, vimentin in connective tissues)

    Microtubules

    • Largest of the cytoskeletal filaments
    • Composed of tubulin dimers (alpha and beta)
    • Assemble at microtubule-organizing centers (MTOCs) like centrosomes
    • Exhibit dynamic instability, meaning they can grow and shrink rapidly
    • Involved in cell division, intracellular transport, and maintaining cell shape.

    Dynamic Instability

    • A unique property of microtubules
    • Regulated growth and shrinking of microtubules as needed
    • GTP hydrolysis controls dynamic instability
    • The addition or removal of tubulin dimers happens at the + (positive) end
    • Critical concentration governs the rate of addition and removal of tubulin.

    Cilia and Flagella

    • Microtubules are involved in their assembly and movement
    • Arrangement of 9 doublets of microtubules plus two singlet microtubules (9+2)
    • Motor proteins (e.g., dynein) and ATP are involved

    Transport

    • Motor proteins (e.g., kinesin, dynein) move cargo along microtubules.
    • Cargo can include proteins, organelles, or vesicles
    • Cargo movement depends on motor protein direction relative to the plus and minus end of microtubules.

    Endomembrane Functions

    • Involved in synthesis, modification, sorting, and transport of proteins and lipids
    • Includes the ER, Golgi, lysosomes, and other organelles.

    Vesicle Formation

    • Coat proteins (like clathrin and COP proteins) are important for vesicle formation
    • Coat proteins bind to membrane proteins that need to be transported
    • This binding initiates the formation of a vesicle
    • Vesicles fuse with target membranes to deliver their cargo.

    Cell Signaling

    • Endocrine, paracrine, and synaptic signaling are different types of communication between cells
    • They involve signaling molecules that bind to receptors on target cells
    • Signaling pathways involve protein activation and phosphorylation.
    • Water-soluble and lipid-soluble molecules have different mechanisms for binding.

    G-protein Coupled Receptors (GPCRs)

    • Membrane receptors that interact with G proteins
    • Activation of GPCR results in G protein dissociation and activation of downstream signaling pathways
    • G proteins are involved in both fast and slow responses.

    Enzyme-coupled receptors (RTKs)

    • Transmembrane receptors which involve a phosphorylation cascade.
    • Activated receptors lead to the activation of secondary signaling molecules
    • Receptors are involved in intracellular signaling and regulate various cellular activities like protein synthesis or cell death.

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