key term - Contractile ring

Definition

The contractile ring is a structure formed during cytokinesis, the final stage of cell division, that helps to physically separate the daughter cells. It is made up of a band of actin filaments and myosin motors that constrict the cell membrane, leading to the formation of two distinct cells from one parent cell. This process is crucial for proper cell division and plays an important role in maintaining cellular integrity.

5 Must Know Facts For Your Next Test

1. The contractile ring forms just beneath the plasma membrane during late anaphase and early telophase.
2. It is primarily composed of actin and myosin, which interact to produce the force needed for constriction.
3. The contraction of the ring leads to a cleavage furrow, which deepens as the ring tightens, eventually pinching the cell into two separate entities.
4. Proper formation and function of the contractile ring are essential for successful cytokinesis; errors can result in multinucleated cells or failed cell division.
5. In some organisms, like certain plants and fungi, alternative mechanisms like cell plate formation are used instead of a contractile ring for cytokinesis.

Review Questions

• Explain the role of the contractile ring in cytokinesis and how it contributes to cell division.
  • The contractile ring plays a vital role in cytokinesis by forming a physical barrier that separates the cytoplasm of the dividing cell into two daughter cells. During late anaphase and early telophase, actin filaments and myosin proteins assemble to create this ring just beneath the plasma membrane. As the ring contracts, it creates a cleavage furrow that deepens until the membrane is pinched apart, ensuring that each daughter cell receives an appropriate share of cytoplasmic components.
• Discuss what happens if there is a malfunction in the contractile ring during cell division.
  • If there is a malfunction in the contractile ring during cell division, it can lead to incomplete cytokinesis, resulting in multinucleated cells or even failure to separate entirely. This improper division may disrupt cellular function and can contribute to various issues, including cancerous growths where cells divide uncontrollably. Understanding these malfunctions helps researchers develop targeted therapies to address conditions arising from faulty cell division.
• Analyze how the composition of the contractile ring influences its function and efficiency during cytokinesis.
  • The composition of the contractile ring is crucial for its function and efficiency during cytokinesis as it primarily consists of actin filaments and myosin motors. The interaction between these proteins enables contraction, providing the mechanical force necessary for the physical separation of daughter cells. Variations in the concentrations or organization of these proteins can impact how effectively the ring constricts and completes cytokinesis. This highlights how protein dynamics within the contractile ring are tightly regulated to ensure successful cell division.

Related terms

cytokinesis:

The process by which the cytoplasm of a parental cell divides into two daughter cells, usually occurring after mitosis or meiosis.

mitosis:

A type of cell division that results in two genetically identical daughter cells, crucial for growth and repair in multicellular organisms.

actin filaments:

Thin protein fibers that are part of the cytoskeleton and play a key role in various cellular processes, including maintaining cell shape and enabling movement.