21 Questions
What is the result of ATP binding to myosin?
Release of myosin from actin
What is the role of transverse tubules in muscle contraction?
To transmit impulses from action potentials to the interior of the cell
What is the source of calcium ions needed for muscle contraction?
Sarcoplasmic reticulum
What is the result of calcium binding to troponin?
A change in conformation that allows muscle contraction
How many myosin molecules interact with each filament?
Approximately 100
What is the role of microtubules in cellular transport, and what structures do they support?
Microtubules act as 'roads' through the cell, allowing for specific transport of materials to a given target, and they support the structure of axons.
What are the three broad classes of motor proteins, and what are their corresponding pathways?
The three broad classes of motor proteins are kinesins, dyneins, and myosins, which use microtubule pathways, microtubule pathways, and microfilaments, respectively.
How do kinesins move along microtubules, and what determines the direction of their movement?
Kinesins move along microtubules through the binding and hydrolysis of ATP, causing conformational changes, and the direction of their movement is determined by the neck region of the molecule.
What is the role of cytoplasmic dynein in cellular transport, and in which direction does it move along microtubules?
Cytoplasmic dynein is involved in positioning of the spindle and chromosome movement, and it moves towards the minus end of the microtubule.
What is the function of microtubule depolymerases, and in which cellular processes are they involved?
Microtubule depolymerases are a small group of kinesins involved in microtubule depolymerization, and they are critical in cell division processes.
What is the proposed model for the use of kinesins and dyneins in cellular transport, and how do they interact with vesicles?
The proposed model suggests that kinesins and dyneins are involved in cellular transport based on microtubule polarity, and vesicles may have both types of motor proteins bound at one time, leading to a tug-of-war mechanism.
What are the two ends of microfilaments assembled from monomers?
barbed and pointed ends
What is the minimum number of classes of myosin identified, and how many different myosins are found in humans?
17 classes, 40 different myosins
What is the function of the head of myosin Type II in relation to the microfilament?
moves towards the (+) end of the microfilament
What is the role of unconventional myosin I in the cell?
acts as an attachment point for microfilaments to the plasma membrane
What is the primary function of unconventional myosins in terms of transport?
transport of vesicles and organelles, or as organelle tethers
What are the contractile units of skeletal muscle cells called?
sarcomeres
What is the function of troponin in the sarcomere?
interacts with the end of tropomyosin and with actin
What is the function of titin in the sarcomere?
maintains overall structure, aids relaxation
What is the result of the conformational change of the myosin filament head during contraction?
moves the actin filament 10 nm
What is the organization of the thick filaments in the sarcomere?
composed of several hundred myosin molecules with bipolar orientation
Test your knowledge of motor proteins and their role in cellular transport and contraction. Learn about microtubule networks, neurofilaments, and the transport of organelles, vesicles, and molecules. Based on Karp's Cell and Molecular Biology (2020) Fig 9.7.
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