Question

1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. 2. Many cell organelles, most notably the nucleus, are anchored by microtubules which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microfilaments. 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microtubules. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments. 6. During muscle contractions, myosin motor proteins move across tracks of microtubules.

Answer 1

Answer:

1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. True

2. Many cell organelles, most notably the nucleus, are anchored by microtubules which are assembled from a diverse class of proteins. False

3. Centrosomes are sites where protein dimers assemble into microfilaments. False

4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microtubules. False

5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments. True

6. During muscle contractions, myosin motor proteins move across tracks of microtubules. False

Explanation:

2. Most cell organelles are anchored by intermediate filaments, this kind of filaments are formed by fibrous proteins and they are one of the main elements of the cytoskeleton.

3. Centrosomes are sites where protein dimers assemble into microtubules that the cell needs to move organelles, vesicles, and chromosomes during cell division.

4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments, which have a similar function to microtubules as they also provide movement. Intermediate filaments are part of the structure, but they do not provide any movement.

6. During muscle contractions, myosin motor proteins move across tracks of microfilaments, as they are a structural component, they form tracks so that the proteins can go to a specific site.

In conclusion, Microfilaments are the ones that serve as tracks for the movement of myosin.

Microtubules provide structural support and movement to vesicles and organelles, they do this by adding and removing tubulin from their ends. The tubulin that is removed from one end is added to the other end.

Intermediate filaments have a structural role anchoring organelles and keeping the shape of the cell. Their size is intermediate between the microtubules, which are the largest, and microfilaments, which are the smallest.

Answer 2

Answer:

1) In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules.

2) Many cell organelles, most notably the nucleus, are anchored by intermediate filaments which are assembled from a diverse class of proteins.

3) Centrosomes are sites where protein dimers assemble into microtubules.

4) The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments.

5) The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments.

6) During muscle contractions, myosin motor proteins move across tracks of microfilaments.

Explanation:

The cytoskeleton is a very important element of the cell, and is composed of three different structures: microtubules, intermediate filaments, and microfilaments.

Microtubules are structures in the shape of hollow tubes that give shape to the cell. Microtubules also participate in cell motility by providing a route for the organelles to move through.

Intermediate filaments are the only ones that do not participate in cell motility: their main function is to provide mechanical support for the plasma membrane.

Microfilaments are a key component in cell motility, and also associate with myosin (a protein) to produce muscle contraction. Microfilaments also give the cell the ability to grow pseudopods.