--- title: "Motor Proteins and Directed Movement Along Tracks" description: "Myosins, kinesins and dyneins use ATP-dependent cycles to generate movement on polar filaments. Direction depends on the particular motor and the track's orientation. Opposite-direction motors support" canonical: https://lightmysky.com/learn/science/motor-proteins-and-directed-movement-along-tracks-mt_TUTmILr7y0 source: https://lightmysky.com/learn/science/motor-proteins-and-directed-movement-along-tracks-mt_TUTmILr7y0.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Motor Proteins and Directed Movement Along Tracks Myosins, kinesins and dyneins use ATP-dependent cycles to generate movement on polar filaments. Direction depends on the particular motor and the track's orientation. Opposite-direction motors support transport both ways along a track. Subject: Science · Area: Organisms & Life Processes · Ages 20 to 22 Page: https://lightmysky.com/learn/science/motor-proteins-and-directed-movement-along-tracks-mt_TUTmILr7y0 ## Ready when they can - Explains how ATP binding and hydrolysis support the muscle myosin cross-bridge cycle without assigning that cycle to every motor. - Predicts which way a cargo travels given the motor and the track polarity. - Explains why a cell needs motors moving in both directions along the same track. ## Lesson: Motor cycles and track direction Motors use ATP-dependent changes in shape and attachment to generate movement. Their cycles differ. In muscle myosin, ATP binding releases the head from actin; hydrolysis resets it. The head attaches again, phosphate release accompanies the power stroke, and ADP leaves. One ATP is used per cross-bridge cycle. One ATP per exact step is not a rule for every motor, and a motor can pause or take a backward step. *(drawing: This sequence describes muscle myosin. Other motors have different ATP-dependent cycles.)* Myosins use actin; kinesins and dyneins use microtubules. Conventional kinesin-1 usually moves toward plus ends, while cytoplasmic dynein moves toward minus ends. Some other kinesins move toward minus ends or change filament length instead of hauling cargo. Most myosins move toward actin plus ends, but myosin VI moves toward the minus end. Name the particular motor when predicting direction. Plus does not always mean outward, or minus inward. Read the track orientation. On a microtubule with its minus end at the center and plus end at the edge, kinesin-1 carries cargo outward and dynein carries it inward. Reverse the track and those spatial directions reverse. Cells regulate opposite-direction motors so cargo can travel both ways. A trip does not always require a handoff. *(drawing: The route depends on the stated track orientation. The boxes are not a drawing of the filament.)* **Example.** In skeletal muscle, calcium binds troponin. Tropomyosin moves away from myosin-binding sites on actin, permitting cross-bridge cycling while ATP is available. Heads contribute at different times, rather than pulling in unison. After a power stroke, a bound head needs new ATP to detach. Without it, repeated cycling cannot continue. Microtubules often support long-distance transport, including transport along axons. Actin and myosin often support local delivery and tension near the membrane. These are common arrangements, not exclusive rules about distance or location. Available tracks and motors determine how cargo is delivered. Motor transport also differs from force generated by filament assembly, such as actin pushing a leading edge. **Recap.** Motor cycles differ. Predict cargo direction from the named motor and track orientation. Common transport roles are not exclusive rules. *Lesson, questions and flashcards written for this dataset.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Microtubules, Dynamic Instability and the Spindle](https://lightmysky.com/learn/science/microtubules-dynamic-instability-and-the-spindle-mt_RWhMJxOmUu) ## Optional connections - [The Sliding Filament Model of Muscle Contraction](https://lightmysky.com/learn/science/the-sliding-filament-model-of-muscle-contraction-mt_BsB4s4HfD8) ## Opens up - [Junctions, Adhesion and the Extracellular Matrix](https://lightmysky.com/learn/science/junctions-adhesion-and-the-extracellular-matrix-mt_Sjcd3kQUmw)