In a neuron, mitochondrial biogenesis is believed to occur primarily in the cell body, but mitochondria are often positioned at the presynaptic terminal, a distal site with high metabolic demand. Given this information, which molecular mechanism is most likely responsible for mitochondrial transport from the cell body to the presynaptic terminal?

Question

In a neuron, mitochondrial biogenesis is believed to occur primarily in the cell body, but mitochondria are often positioned at the presynaptic terminal, a distal site with high metabolic demand.  Given this information, which molecular mechanism is most likely responsible for mitochondrial transport from the cell body to the presynaptic terminal?

Quizplus · Accepted Answer

11ecba2d_0fd3_8e3f_a3bf_25ad4e9d7787_MD0008_00 A eukaryotic cell's cytoskeleton is an intracellular scaffolding (network) of fibers interspersed throughout the cytoplasm. The cytoskeleton is composed of three types of fibers: Microfilaments, intermediate filaments, and microtubules. Together, these fibers function to organize cellular components, support cellular motility (eg, cell movement, intracellular transport), and give the cell its shape. Microtubules are structural cytoplasmic filaments composed of tubulin subunits. These filaments have a number of critical functions, including serving as tracks for intracellular transport of organelles and vesicles. The movement of intracellular cargo along microtubules is mediated by two motor proteins: Kinesin: Moves intracellular cargo along microtubules in anterograde axonal transport (ie, away from the nucleus and toward distal sites). Dynein: Participates in retrograde axonal transport of intracellular cargo (ie, from distal sites toward the nucleus) (Choice D). According to the question, mitochondria are transported from the cell body toward the presynaptic terminal. Because mitochondria are being transferred from the nucleus and toward the synaptic terminal, this anterograde transport is most likely being performed by kinesin motors moving along the microtubules. (Choices B and C) Movement along actin microfilaments occur via myosin motors (not kinesin or dynein). The primary functions of myosin movement along microfilaments are cellular locomotion, cellular division, and muscle contractions. Educational objective: The intracellular scaffolding of a eukaryotic cell is composed of three families of protein filaments: Microfilaments, intermediate filaments, and microtubules. Intracellular transport of cargo (eg, organelles, vesicles) is mediated primarily by two microtubular motor proteins (kinesin and dynein). Kinesin mediates anterograde transport (ie, away from the nucleus) whereas dynein mediates retrograde transport (ie, toward the nucleus).

In a Neuron, Mitochondrial Biogenesis Is Believed to Occur Primarily