Unit 6: Molecular motors and mechanobiology - Practice Quiz

1 Which molecule serves as the primary energy source for molecular motors like kinesin and myosin?

2 Along which cytoskeletal filament does the motor protein myosin move?

3 Along which cytoskeletal track do kinesin and dynein move?

4 In most cells, kinesin generally transports cargo toward which end of the microtubule?

5 In which direction along the microtubule does cytoplasmic dynein typically move?

6 Which molecular motor is primarily responsible for muscle contraction?

7 What general term describes the movement of vesicles and organelles within a cell along cytoskeletal tracks?

8 The part of a motor protein that binds and hydrolyzes ATP is commonly called the:

9 Which part of a motor protein such as kinesin usually attaches to the cargo being transported?

10 Molecular motors are best classified as which type of biological molecule?

11 Microtubules are built from which protein subunit?

12 The basic building block of a microtubule is a dimer made of which two proteins?

13 What is the overall shape of a microtubule?

14 How many protofilaments typically make up a single microtubule?

15 Microtubules are described as polar structures because they have:

16 Microtubules are a component of which cellular structure?

17 Mechanobiology mainly studies how cells respond to what kind of signals?

18 The process by which cells convert mechanical signals into biochemical responses is called:

19 Which structure surrounding cells provides mechanical support and transmits forces in tissues?

20 Understanding mechanobiology is important in human health because abnormal mechanical signaling can contribute to:

21 A vesicle needs to be transported from the cell center toward the plus-end of a microtubule near the cell periphery. Which motor protein is most likely responsible for this movement?

22 During retrograde axonal transport, damaged organelles move from the axon terminal back toward the cell body. Which motor drives this movement?

23 Myosin motors primarily move along which cytoskeletal filament?

24 Kinesin is described as a 'processive' motor. What does processivity mean in this context?

25 Conventional kinesin moves along a microtubule using a 'hand-over-hand' mechanism with an approximate step size of:

26 What is the primary energy source that powers the walking motion of kinesin and dynein motors?

27 In muscle contraction, the sliding filament model relies on which myosin activity?

28 Melanophores can rapidly aggregate or disperse pigment granules. Dispersion toward the cell periphery is mainly driven by:

29 Which structural feature of kinesin allows two heads to coordinate their ATPase cycles for processive walking?

30 A typical microtubule is composed of how many protofilaments arranged into a hollow cylinder?

31 Microtubules are polar structures. This polarity arises because:

32 The dynamic behavior in which individual microtubules switch between growth and rapid shrinkage is called:

33 Which nucleotide state of tubulin at the microtubule end promotes stability and continued growth?

34 The building block of microtubules is a heterodimer consisting of:

35 In animal cells, microtubule minus-ends are typically anchored at the:

36 The anti-cancer drug Taxol (paclitaxel) affects microtubules by:

37 Mechanotransduction refers to the process by which cells:

38 Stem cells cultured on substrates of different stiffness can differentiate along distinct lineages. Cells grown on a soft, brain-like matrix tend to become:

39 Which cell-surface structures physically link the extracellular matrix to the intracellular cytoskeleton and sense mechanical force?

40 Endothelial cells lining blood vessels sense blood flow. The relevant mechanical stimulus they primarily detect is:

41 Conventional kinesin-1 moves processively along microtubules by a hand-over-hand mechanism. If one head detaches before the trailing head has completed its ATP-dependent power stroke, the motor risks dissociation. Which coordination feature most directly prevents both heads from releasing simultaneously?

42 A kinesin motor takes discrete 8 nm steps and hydrolyzes one ATP per step. If a single motor sustains an average velocity of under low load, what is its approximate ATP turnover (stepping) rate?

43 Cytoplasmic dynein differs fundamentally from kinesin in its stepping behavior. Which observation best reflects dynein's structural mechanism of force generation?

44 In an in vitro motility assay, myosin V walks processively along actin with 36 nm steps, while myosin II is non-processive. What structural feature primarily accounts for myosin V's processivity relative to myosin II?

45 A neuron transports cargo bidirectionally along an axon. Anterograde and retrograde vesicle movements often reverse rapidly on the same track. The most widely supported explanation for this bidirectional switching is:

46 The stall force of a single kinesin-1 is about over an step. Comparing the mechanical work per step to the free energy of ATP hydrolysis ( under cellular conditions), the approximate thermodynamic efficiency is:

47 Optical-trap experiments show that when kinesin's neck linker is artificially lengthened, processivity and velocity both drop sharply. This is best explained because a longer neck linker:

48 Microtubules are built from -tubulin heterodimers arranged into protofilaments. The structural basis for microtubule polarity, essential for directed motor transport, is that:

49 A typical microtubule has 13 protofilaments arranged with a slight lateral stagger, creating a helical 'seam.' The functional significance of the 13-protofilament, B-lattice arrangement is that it:

50 Dynamic instability of microtubules is governed by the nucleotide state of -tubulin. The transition from growth to rapid shrinkage (catastrophe) occurs when:

51 Consider a microtubule with 13 protofilaments and a tubulin dimer length of . If the microtubule elongates by adding 260 dimers total distributed evenly, by how much does its length increase?

52 Post-translational modifications (PTMs) such as detyrosination, acetylation, and polyglutamylation form the 'tubulin code.' A key functional consequence relevant to intracellular transport is that PTMs:

53 Taxol (paclitaxel) is a chemotherapeutic that binds -tubulin. Its anti-mitotic effect arises because taxol:

54 Cells sense the stiffness of their extracellular matrix (ECM) and translate it into biochemical signals — a process called mechanotransduction. Which molecular event is central to converting matrix stiffness into altered gene expression?

55 Mesenchymal stem cells cultured on substrates of differing stiffness differentiate along distinct lineages. On a stiff, bone-like matrix (–), the predominant outcome is:

56 Piezo1 is a mechanically gated ion channel important in vascular and epithelial physiology. Its gating mechanism is best described as:

57 Tumor progression is associated with ECM stiffening. Increased matrix stiffness promotes malignancy primarily by:

58 Endothelial cells lining blood vessels respond to laminar shear stress from blood flow. Physiological laminar shear is generally atheroprotective because it:

59 In muscular dystrophies, mutations in the dystrophin–glycoprotein complex cause fiber damage. From a mechanobiology standpoint, the core defect is that:

60 The LINC complex (SUN and nesprin proteins) spans the nuclear envelope. Its role in mechanobiology is to: