Problem 10 - Campbell Biology Concepts & Connections

Question

Cytochalasin \(\mathrm{B}\) is a chemical that disrupts microfilament formation. This chemical would interfere with a. DNA replication. b. formation of the mitotic spindle. c. cleavage. d. formation of the cell plate.

Step-by-Step Solution

Answer

c. cleavage

Step 1: Understand the Role of Microfilaments

Microfilaments, composed of actin, are part of the cytoskeleton. They are crucial for various cellular processes, including maintaining cell shape, enabling cell movement, and facilitating cytokinesis (the division of a cell's cytoplasm).

Step 2: Identify the Processes Listed

Review the processes listed in the options: DNA replication, formation of the mitotic spindle, cleavage, and formation of the cell plate. Understand which of these processes involve microfilaments.

Step 3: Analyze Each Option

a. DNA replication does not directly rely on microfilaments but rather on factors within the nucleus. b. The formation of the mitotic spindle primarily involves microtubules, not microfilaments. c. Cleavage, particularly during cytokinesis, directly involves microfilaments as they contract to divide the cell. d. The formation of the cell plate, pertinent to plant cells, involves microtubules and vesicles more than microfilaments.

Step 4: Select the Correct Answer

Given the role of microfilaments in cleavage, particularly in the contractile ring during cytokinesis, the correct answer is c. cleavage.

Key Concepts

microfilaments

Microfilaments are thin, thread-like structures made of the protein actin. They are essential components of the cytoskeleton, which is the cellular framework that provides structure and support to the cell. Microfilaments play several critical roles within the cell:

• They help maintain cell shape by forming a dense network just beneath the plasma membrane.
• They enable cell movement by facilitating cellular contractions, which are essential for processes like amoeboid movement and muscle contraction.
• They participate in intracellular transport by helping move vesicles and organelles within the cell.
• They are crucial for cytokinesis, the process during which a cell's cytoplasm divides during cell division.

The disruption of microfilament formation, such as by the chemical cytochalasin B, can thus interfere with these vital cellular functions.

cytokinesis

Cytokinesis is the final stage of cell division, where the cytoplasm of a parent cell is divided into two daughter cells. This process ensures that each daughter cell receives the necessary cellular components to survive and function properly.
Cytokinesis involves the formation of a contractile ring composed of microfilaments and myosin, another protein. The contractile ring tightens around the cell, much like a drawstring, pinching the cell membrane and eventually splitting the parent cell into two separate entities. In animal cells, this process results in the formation of a cleavage furrow.
Disruption of microfilament formation by chemicals such as cytochalasin B thus impairs cytokinesis. Without proper microfilament function, the contractile ring cannot form or operate efficiently, preventing the cell from successfully dividing its cytoplasm.

cell division

Cell division is the process by which a parent cell divides into two or more daughter cells. It is a fundamental biological process essential for growth, development, and tissue repair. Cell division occurs in two main stages: mitosis and cytokinesis.
Mitosis is the division of the cell's nucleus and distribution of its genetic material into two daughter nuclei. It consists of several phases: prophase, metaphase, anaphase, and telophase.
During cytokinesis, the cytoplasm divides, and the daughter cells are fully separated. While mitosis ensures that each daughter cell receives an identical set of chromosomes, cytokinesis ensures that each cell receives sufficient cytoplasmic contents.
In summary, proper cell division is crucial for organismal development and maintenance. Interfering with any part of this process, such as disrupting microfilaments and thereby hindering cytokinesis, can have significant impacts on cellular function and overall health.