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Motor Proteins & Filaments Moving in the Cell

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Motor Proteins & Filaments Moving in the Cell δ Name: ________________ Period: ____ Motor Proteins & Filaments Moving in the Cell Motor Proteins You’ve already learned about proteins and how they usually operate (recall what you learned about active sites, substrates, and the lock & key analogy). As previously discussed, proteins are used for many different jobs in your body. This worksheet will focus on a specific type of protein: Motor Proteins. Motor proteins are proteins that generate movement. Motors, like the motors in machines such as electric cars, are what convert energy into movement. The “motor” part of the term “motor protein” means that these special kinds of proteins work the same way. Just like how a motor needs to be supplied with energy (in the form of electricity) in order to move, a motor protein needs to be supplied with energy in order to move. The diagram below shows one special kind of motor protein called Kinesin, and how it uses a special kind of energy (chemical energy stored in a molecule called ATP) to move. The “tail” section of Kinesin grabs onto things inside of a cell (labeled “transport vesicle” in the diagram above), and the two “heads” of Kinesin grip onto a track that runs across the entire cell. When ATP reaches an active site on the head of Kinesin, it takes a step forward. Every step that Kinesin wants to make, it needs a molecule of ATP to do it. You can imagine this protein like it’s a motorcycle; if you want your motorcycle to drive down the street, you need to make sure it has gas in its tank. If you stop giving it gas or it runs out, it stops moving. If the motorcycle stops moving, you get stranded on the street and can’t get where you need to go. Without motor proteins like Kinesin, things inside your cells would take a lot longer to get where they need to go. In some cases, they wouldn’t be able to get there at all. Here’s another analogy that may help you understand why motor proteins are necessary: A river flows in one direction. If you put a paper boat on that river, you can expect it to flow downstream with the water, but what if you wanted to get something to a location upstream? If you put a motor on the boat, then it could fight the direction of the flow of the water and get upstream. There are some locations in your cells that you can consider “upstream” – places that certain materials either can’t get to without help or are difficult to get to. Motor Proteins are like speedboats you can use to drive up a stream to transport materials: fast, goes only down a set path, and allows you to move things in a direction you couldn’t otherwise move them. Filaments These “tracks,” “rivers,” or “streets” that Kinesin walks down are actually a type of Filament. Filaments are long, rope-like structures that run through the cytoplasm in a cell. There are three different types of filaments in a cell, all Joanis - 4/27/2020 δ of which are shown in the table below. The “subunits” that they’re made of are also all proteins, so the filaments themselves are just very large bundles of individual proteins. Actin filaments interact with a different kind of motor protein called Myosin (pictured right). Together, actin and myosin can do the following things: a. Expand and contract to move entire cells from one place to another b. Pinch a cell membrane so that a cell can split into two cells c. Move the cytoplasm in a plant cell around the cell (like water moving in a stream) Intermediate filaments are like anchors or supporting-beams that keep things in the cell in place. Things don’t move along intermediate filaments, and intermediate filaments don’t move either; they stay in place so that important parts of the cell like the nucleus don’t move around. Microtubules are the most important type of filament for moving things inside of the cell. The types of filaments that Kinesin walk on are microtubules. They’re like the streets and highways of the cell, and Kinesin and some other motor proteins are the trucks that carry cargo from one place to another. They extend all throughout the cell, originating from (coming from) the centrosomes (pictured below). Joanis - 4/27/2020 δ Answer the following questions to show your understanding of motor proteins and filaments. Answer each question using full sentences. The more developed/detailed your answer, the better. If you don’t know how you would respond to a question, write about why you can’t answer it and what extra information you would need in order to develop an answer: 1. Motor proteins are a type of protein, as their name suggests. Are filaments a type of protein? 2. What special kind of energy does Kinase need in order to do its job? 3. What does Kinase do in a cell? 4. If a cell in your body didn’t have Kinase in it, do you think that cell would be healthy? Explain why or why not. 5. What do you think would happen to a cell that had Kinase, but did not have any microtubules? Explain your answer. Joanis - 4/27/2020 δ 6. All the kinase in a cell was made wrong, and lacks the active cite necessary to accept ATP as a substrate. What will the cell not be able to do? Explain your answer. 7. [CHALLENGE QUESTION] You are attacked by an evil scientist with a devious laser beam that destroys all of the actin filaments in your body! He has also damaged your DNA, so your cells are not able to create any more actin. Would you be able to grow taller if your cells didn’t have any actin filaments? Explain your answer. Joanis - 4/27/2020 .
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