3.3.1 The Cytoskeleton: Basic Components

Question 1

cytoskeleton

Answer 1

• consists of a series of fibers and filaments that are responsible for maintaining the cell’s shape. The three main types of protein fibers are thin microfilaments, medium-sized intermediate filaments, and large microtubules. The cytoskeleton enables structural support and the movement of cell and cell products.

Question 2

microfilaments

Answer 2

• consist of twisted double strands of actin protein and are about 7 nanometers (nm) in diameter. Microfilaments are responsible for muscle contraction,
  formation of the cleavage furrow during cell division, and movement of pseudopodia.
• The contraction of muscle fibers occurs by anchoring microfilaments to proteins. A defect in dystrophin, one such anchoring protein, results in muscular dystrophy, a debilitating human disorder.

Question 3

intermediate filaments

Answer 3

• consist of rope-like proteins and include the keratin family. They are approximately 8-12 nm in diameter.

Question 4

microtubes

Answer 4

• are about 25 nm in diameter. They are arranged in a spiral of protein subunits.
• During cell division, microtubules move the chromosomes into the daughter nuclei.

Question 5

actin

Answer 5

• a globular protein of which microfilaments are made

Question 6

Which of the following is a major difference between microtubules and microfilaments.

a. Microtubules are formed from fibrous proteins such as keratins seemingly woven together, whereas microfilaments are made of small actin subunits.
b. Microfilaments are much larger than microtubules.
c. Microtubules are hollow cylindrical molecules, whereas microfilaments are not.
d. Microfilaments are composed of protein subunits whereas microtubules are not.

Answer 6

• c. Microtubules are hollow cylindrical molecules, whereas microfilaments are not

Question 7

Which of the following are components of a eukaryotic cell’s cytoskeleton?

Answer 7

• actin filaments, microtubules, and intermediate filaments

Question 8

Which of the following is not a function of microtubules?

Answer 8

• movement of muscle fibers

Question 9

Microtubules play an integral role in __________, while the microfilaments are involved in __________.

Answer 9

• the movement of chromosomes, cell division

Question 10

The cytoskeleton of a cell functions to

Answer 10

• allow organelles to move.
• anchor organelles.
• provide structure and support.