Motor Proteins in Cellular Transport and Contraction

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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 Signup and view all the answers

How many myosin molecules interact with each filament?

Approximately 100 Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

What are the two ends of microfilaments assembled from monomers?

barbed and pointed ends Signup and view all the answers

What is the minimum number of classes of myosin identified, and how many different myosins are found in humans?

17 classes, 40 different myosins Signup and view all the answers

What is the function of the head of myosin Type II in relation to the microfilament?

moves towards the (+) end of the microfilament Signup and view all the answers

What is the role of unconventional myosin I in the cell?

acts as an attachment point for microfilaments to the plasma membrane Signup and view all the answers

What is the primary function of unconventional myosins in terms of transport?

transport of vesicles and organelles, or as organelle tethers Signup and view all the answers

What are the contractile units of skeletal muscle cells called?

sarcomeres Signup and view all the answers

What is the function of troponin in the sarcomere?

interacts with the end of tropomyosin and with actin Signup and view all the answers

What is the function of titin in the sarcomere?

maintains overall structure, aids relaxation Signup and view all the answers

What is the result of the conformational change of the myosin filament head during contraction?

moves the actin filament 10 nm Signup and view all the answers

What is the organization of the thick filaments in the sarcomere?

composed of several hundred myosin molecules with bipolar orientation Signup and view all the answers