Question

Our cell can divide itself once approximately in (a) 24 hours (b) 24 minutes (c) 24 seconds (d) 24 days

Short answer

(a) 24 hours

Step-by-step solution

Understanding the question

The exercise asks for the approximate length of time it takes for a cell to divide. This depends on the type of cell and various factors. The most common cell type referred to in a biological context is a typical human cell.

Identifying the correct answer

Looking at the options given, the correct answer for a typical human cell under normal conditions is approximately 24 hours. This includes all phases of the cell cycle, which are interphase, mitosis, and cytokinesis.

Key concepts

The Cell Cycle

When we talk about the time it takes for a cell to divide, we're referring to the duration of the cell cycle. The cell cycle is a series of events that take place in a cell, leading to its division and replication. It is typically divided into four phases: G1 (gap 1), S (synthesis), G2 (gap 2), and M (mitosis). During G1, the cell grows and carries out normal functions. The S phase is critical because this is where DNA replication occurs. G2 involves further growth and preparation for division. Lastly, M phase is where the actual division occurs, consisting of mitosis and cytokinesis.

In humans, this cycle tends to take about 24 hours, with a significant portion of the time consumed in interphase (G1, S, and G2). It's vital to understand that the length can vary based on cell type, with some cells dividing faster and others slower. For instance, embryonic cells can divide faster than adult cells due to the rapid growth requirements.

Importance of Cell Cycle Regulation

Regulation of the cell cycle is crucial for maintaining healthy tissue function. Disruptions can lead to cell death or uncontrolled cell growth, such as in cancer. Cells have checkpoint mechanisms to ensure each phase is correctly completed before moving on to the next stage, safeguarding the fidelity of cell division.

Mitosis

Mitosis is a specific part of the cell cycle where the nucleus divides. It is typically divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. During prophase, the chromatin condenses into discrete chromosomes, and the mitotic spindle begins to form. Prometaphase is marked by the breakdown of the nuclear membrane. In metaphase, chromosomes line up at the cell's equator. Anaphase is where sister chromatids separate and move to opposite poles of the cell. Lastly, in telophase, the chromosomes decondense, and the nuclear membranes reform.

This process ensures that each new cell receives an identical set of chromosomes. Mitosis is highly orchestrated, and errors can cause genetic abnormalities. Mitotic duration can range from less than an hour to a few hours, depending on the cell type and environmental conditions.

Cytokinesis

Cytokinesis is the process that follows mitosis, where the cell's cytoplasm divides, creating two daughter cells. This stage is crucial as it completes the process of cell division. In animal cells, a structure known as the cleavage furrow forms and pinches the cell into two. In plant cells, a cell plate forms along the centerline of the cell, leading to the development of a new cell wall that will separate the two new cells.

The process of cytokinesis varies in time, but for a human cell, it's usually swift, completing within an hour or so after mitosis. It's also noteworthy that cytokinesis must be tightly coordinated with mitosis; any miscoordination can lead to cells with inappropriate size or number of organelles that may not function properly.

The Outcome of Cytokinesis

Successful cytokinesis results in two genetically identical daughter cells, each with the correct amount of cytoplasm and organelles necessary for normal function. This crucial process underscores the importance of accurate cell division and is essential for growth, development, and tissue repair in multicellular organisms.