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Chapter 1: Problem 12

There are three major classes of filaments that make up the cytoskeleton. What are they, and what are the differences in their functions? Which cytoskeletal filaments would be most plentiful in a muscle cell or in an epidermal cell making up the outer layer of the skin? Explain your answers.

Short Answer

Expert verified
Muscle cells contain abundant microfilaments for contraction, while epidermal cells have plentiful intermediate filaments for strength.

Step by step solution

01

Identify the Three Major Classes of Filaments

The three major classes of filaments that comprise the cytoskeleton are microtubules, intermediate filaments, and microfilaments (or actin filaments). Each has unique structures and functions within the cell.
02

Understand the Function of Microtubules

Microtubules are hollow tubes made of tubulin proteins. They are crucial for maintaining cell shape, enabling intracellular transport, and separating chromosomes during cell division.
03

Learn About Intermediate Filaments

Intermediate filaments provide mechanical strength to cells and help maintain their integrity. They are more permanent structures compared to other filaments and can vary depending on the cell type, such as keratin in epithelial cells.
04

Explore the Role of Microfilaments

Microfilaments, composed of actin, are involved in muscle contraction, cell motility, and maintaining cell shape. They are dynamic structures that can rapidly assemble and disassemble.
05

Identify the Filaments Most Plentiful in Muscle Cells

In muscle cells, microfilaments are most abundant due to their role in muscle contraction. Actin filaments interact with myosin to facilitate contraction and movement.
06

Determine Which Filaments Are Plentiful in Epidermal Cells

Epidermal cells primarily contain intermediate filaments, particularly keratin, which provides the strength needed to form the protective outer layer of the skin.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Microtubules
Microtubules are like the cell's highways. They are sizable, hollow tubes made of tubulin protein subunits. These tubes are strong yet flexible, creating a dynamic network within the cell that supports a variety of functions.

**Key functions of microtubules include:**
  • Maintaining cell structure: They provide a backbone of sorts that helps the cell keep its shape.
  • Acting as tracks for intracellular transport: Motor proteins travel along these microtubules to transport organelles, vesicles, and other cellular components to their required destinations within the cell.
  • Playing a role in cell division: Microtubules form the mitotic spindle, which is crucial for chromosome separation during cell division.

These functionalities make microtubules essential for both everyday cellular processes and specialized tasks like cell division. They are continuously assembled and disassembled, adapting to the cell's current needs, making them a vital component of the cytoskeleton.
Intermediate Filaments
Intermediate filaments are the cell's anchoring system. Unlike the more dynamic microtubules and microfilaments, intermediate filaments are sturdy, rope-like structures that provide mechanical support to cells.

**Functions of intermediate filaments include:**
  • Providing rigidity and strength: They are essential for maintaining cell integrity, helping cells withstand mechanical stresses without being damaged.
  • Cell type variability: They come in several types, depending on the cell. For instance, keratin filaments are predominant in skin cells, while vimentin is common in mesenchymal cells.

These filaments do not assemble and disassemble rapidly like microtubules or microfilaments, giving them a more permanent role in the cell鈥檚 internal architecture. They are particularly abundant in cells that experience mechanical stress, such as skin cells, where keratin provides the necessary resilience.
Microfilaments
Microfilaments, composed primarily of actin protein, are the most versatile components of the cytoskeleton. They are the thin threads that play a central role in cell movement and shape changes.

**Major functions of microfilaments include:**
  • Facilitating muscle contraction: They interact with myosin to enable the contraction and relaxation of muscle tissues.
  • Enabling cell movement: Microfilaments are key players in movements such as amoeboid movement, in which cells can crawl along surfaces.
  • Influencing cell shape: They easily assemble and disassemble, allowing the cell to change shape and move in response to its environment.

In muscle cells, microfilaments are highly abundant because of their role in muscle contraction. Actin and myosin filaments work together to facilitate this process. This dynamic nature of microfilaments makes them indispensable for various cellular processes, especially those involving movement and structure.

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Most popular questions from this chapter

When bacteria are grown under adverse conditions, i.e., in the presence of a poison such as an antibiotic, most cells grow and proliferate slowly. But it is not uncommon that the growth rate of a bacterial culture kept in the presence of the poison is restored after a few days to that observed in its absence. Suggest why this may be the case.

Suggest a reason why it would be advantageous for eukaryotic cells to evolve elaborate internal membrane systems that allow them to import substances from the outside, as shown in Figure \(1-24.\)

Apply the principle of exponential growth of a culture as described in Question \(1-13\) to the cells in a multicellular organism, such as yourself. There are about \(10^{13}\) cells in your body. Assume that one cell acquires a mutation that allows it to divide in an uncontrolled manner (i.e., it becomes a cancer cell). Some cancer cells can proliferate with a generation time of about 24 hours. If none of the cancer cells died, how long would it take before \(10^{13}\) cells your body would be cancer cells? (Use the equation \(N=N_{0} \times 2^{t / G},\) with \(t,\) the time, and \(G,\) the length of each generation. Hint: \(10^{13} \approx 2^{43} .\)

Discuss the following statement: "The structure and function of a living cell are dictated by the laws of physics and chemistry."

You have embarked on an ambitious research project: to create life in a test tube. You boil up a rich mixture of yeast extract and amino acids in a flask along with a sprinkling of the inorganic salts known to be essential for life. You seal the flask and allow it to cool. After several months, the liquid is as clear as ever, and there are no signs of life. A friend suggests that excluding the air was a mistake, since most life as we know it requires oxygen. You repeat the experiment, but this time you leave the flask open to the atmosphere. To your great delight, the liquid becomes cloudy after a few days and under the microscope you see beautiful small cells that are clearly growing and dividing. Does this experiment prove that you managed to generate a novel life-form? How might you redesign your experiment to allow air into the flask, yet eliminate the possibility that contamination is the explanation for the results? (For a ready-made answer, look up the classic experiments of Louis Pasteur.)
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