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Questions and Answers
What initiates the power stroke during muscle contraction?
What initiates the power stroke during muscle contraction?
Which statement is true regarding myosin and calcium in muscle contraction?
Which statement is true regarding myosin and calcium in muscle contraction?
What is the role of ATP in muscle contraction?
What is the role of ATP in muscle contraction?
What happens when there is a lack of calcium in muscle contraction?
What happens when there is a lack of calcium in muscle contraction?
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Which step in the muscle contraction cycle involves the hydrolysis of ATP?
Which step in the muscle contraction cycle involves the hydrolysis of ATP?
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What is the primary role of intermediate filaments in a cell?
What is the primary role of intermediate filaments in a cell?
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Which component of the cytoskeleton is responsible for the movement of flagella and cilia?
Which component of the cytoskeleton is responsible for the movement of flagella and cilia?
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How do intermediate filaments differ from globular proteins like chymotrypsin?
How do intermediate filaments differ from globular proteins like chymotrypsin?
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What structural feature allows intermediate filaments to provide tensile strength?
What structural feature allows intermediate filaments to provide tensile strength?
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Which of the following best describes the composition of the nuclear lamina?
Which of the following best describes the composition of the nuclear lamina?
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Which type of cells commonly feature keratin filaments?
Which type of cells commonly feature keratin filaments?
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What does the coiled-coil structure of intermediate filaments primarily help achieve?
What does the coiled-coil structure of intermediate filaments primarily help achieve?
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How do intermediate filaments behave during cellular division?
How do intermediate filaments behave during cellular division?
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What type of cell response is mediated by the cytoskeleton?
What type of cell response is mediated by the cytoskeleton?
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What role do hydrophobic amino acids play in the structure of intermediate filaments?
What role do hydrophobic amino acids play in the structure of intermediate filaments?
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What is the function of myosin in relation to actin filaments?
What is the function of myosin in relation to actin filaments?
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Which steps characterize the process of cell crawling?
Which steps characterize the process of cell crawling?
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What role do actin-binding proteins play in fibroblast migration?
What role do actin-binding proteins play in fibroblast migration?
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In muscle contraction, what primarily causes the sarcomere to shorten?
In muscle contraction, what primarily causes the sarcomere to shorten?
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What distinguishes Myosin-I from Myosin-II?
What distinguishes Myosin-I from Myosin-II?
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How are actin filaments arranged in the sarcomere?
How are actin filaments arranged in the sarcomere?
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What is the key characteristic of muscle myofibrils?
What is the key characteristic of muscle myofibrils?
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What is the role of the Z-disc in a sarcomere?
What is the role of the Z-disc in a sarcomere?
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Which of the following statements about actin filaments during contraction is correct?
Which of the following statements about actin filaments during contraction is correct?
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What is the general structure of myosin molecules?
What is the general structure of myosin molecules?
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What structural role do intermediate filaments primarily serve?
What structural role do intermediate filaments primarily serve?
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Which of the following statements about microtubules is accurate?
Which of the following statements about microtubules is accurate?
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What is the main function of ATP in actin filaments?
What is the main function of ATP in actin filaments?
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Which type of intermediate filament is found in epithelial cells?
Which type of intermediate filament is found in epithelial cells?
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What element primarily anchors microtubules at the centrosome?
What element primarily anchors microtubules at the centrosome?
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What occurs during muscle contractions involving actin and myosin?
What occurs during muscle contractions involving actin and myosin?
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What is a function of motor proteins like kinesins and dyneins?
What is a function of motor proteins like kinesins and dyneins?
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What characterizes the structure of microtubules?
What characterizes the structure of microtubules?
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How do actin filaments contribute to cell movement?
How do actin filaments contribute to cell movement?
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What is the structure of intermediate filaments described as?
What is the structure of intermediate filaments described as?
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Which protein is primarily involved in muscle contractions?
Which protein is primarily involved in muscle contractions?
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What does GTP hydrolysis influence in microtubules?
What does GTP hydrolysis influence in microtubules?
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Which type of filament provides tensile strength to cells?
Which type of filament provides tensile strength to cells?
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Which statement about microtubule growth is correct?
Which statement about microtubule growth is correct?
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What are the main subunits that make up microtubules?
What are the main subunits that make up microtubules?
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Which end of a microtubule is considered the growing end?
Which end of a microtubule is considered the growing end?
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What role do motor proteins play in relation to microtubules?
What role do motor proteins play in relation to microtubules?
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What term describes the process where monomers are simultaneously added to one end and removed from the other end of an actin filament?
What term describes the process where monomers are simultaneously added to one end and removed from the other end of an actin filament?
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What is the diameter of actin filaments?
What is the diameter of actin filaments?
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Which of the following structures involve stable microtubules moved by dynein?
Which of the following structures involve stable microtubules moved by dynein?
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How does GTP hydrolysis affect microtubule growth?
How does GTP hydrolysis affect microtubule growth?
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What is the primary function of microtubules in relation to cell shape?
What is the primary function of microtubules in relation to cell shape?
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What is the role of actin-binding proteins in the dynamics of actin filaments?
What is the role of actin-binding proteins in the dynamics of actin filaments?
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What is the primary structural arrangement of eukaryotic flagella?
What is the primary structural arrangement of eukaryotic flagella?
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What provides ATP energy for motor proteins to function on microtubules?
What provides ATP energy for motor proteins to function on microtubules?
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What type of diseases can result from the disruption of intermediate filaments?
What type of diseases can result from the disruption of intermediate filaments?
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Which of the following best describes the function of microtubules in cell division?
Which of the following best describes the function of microtubules in cell division?
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How are free actin monomers maintained within a cell?
How are free actin monomers maintained within a cell?
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Study Notes
Cytoskeleton Overview
- The cytoskeleton supports cells.
- It's a network of protein filaments throughout the cytoplasm.
- It's involved in organizing and moving intracellular components.
Types of Protein Filaments
-
Intermediate Filaments:
- These filaments provide structural support and withstand mechanical stress.
- They are rope-like, about 10nm in diameter.
- Found throughout the cytoplasm, in the nucleus (nuclear lamina), and sometimes anchoring neighboring cells.
- They fold into coiled-coils.
- Strands form alpha-helices that pair in dimers.
- Hydrophobic amino acids interact to minimize contact with water.
- Dimers wrap to form staggered tetramers and then rope-like filaments.
- Make up the nuclear lamina.
- They respond to stress when cells are stretched.
- Intermediate filaments can be categorized as: keratin, vimentin, neurofilaments, and nuclear lamins.
- Keratin filaments make up skin, hair, claws, and more; humans have more than 50 keratin genes.
- Disruption of intermediate filaments can lead to disease like Epidermolysis bullosa, muscular dystrophy, Neurodegeneration, and Progeria.
-
Microtubules:
- Microtubules have a key role in moving organelles, cell compartments, cell division, and movement of cilia and flagella components.
- Microtubules are hollow tubes composed of alpha- and beta-tubulin.
- They have polarity with a growing (plus) end and a non-growing (minus) end, which is usually anchored.
- Tubulin polymerizes from nucleation sites on a centrosome.
- Gamma (γ) tubulin is the nucleation site that anchors the microtubule.
- GTP hydrolysis controls microtubule growth.
- GTP-bound tubulin molecules bind to the growing end; GDP-bound tubulin molecules are released from the growing end.
- Involves dynamic instability (growing, shrinking).
- They guide movement of organelles, vesicles, and macromolecules.
- Motor proteins (kinesin, dynein) use ATP energy to move along microtubules.
- They are crucial for intracellular transport.
- Cilia and flagella contain stable microtubules moved by dynein.
- They beat in a whip-like fashion, used in things like respiration and sweeping mucus.
- Eukaryotic flagella and cilia have a characteristic 9+2 array with dynein arms.
-
Actin Filaments:
- Actin filaments are essential for cell shape and movement.
- These filaments are composed of globular actin monomers.
- They are about 7nm in diameter.
- Actin filaments are polarized, having plus and minus ends.
- ATP hydrolysis controls actin polymerization.
- High concentrations of actin cause both ends to grow.
- Intermediate concentrations cause treadmilling (monomers removed from minus end added to plus end).
- Actin-binding proteins control the behavior of actin monomers.
- Cell crawling depends on cortical actin.
- It pushes out protrusions to form filopodia and lamellipodia. These attach to the cell surface to cause movement.
- Actin associates with myosin to form contractile structures.
- Myosin uses energy from ATP to pull itself toward the plus end of actin filaments.
- Myosin-I moves organelles along actin, and Myosin-II moves both ends of actin filaments.
Muscle Contraction
- Muscle contraction depends on interacting actin and myosin filaments and involves the sliding of actin filaments past myosin filaments.
- Myosin heads hydrolyze ATP to move along actin, causing contraction.
- Myosin cannot bind to actin in the absence of calcium.
- Tropomyosin blocks myosin binding sites; shifts with Ca2+ binding.
- Muscle contraction involves a cycle: ATP-binding, ATP-hydrolysis, power stroke, and detachment.
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Description
This quiz covers the essential functions and structure of the cytoskeleton, focusing primarily on intermediate filaments. Learn about their role in providing structural support and their various types, including keratin and vimentin. Test your understanding of how these filaments contribute to cellular organization and resilience.
