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Computer generated image of Cancer cell. Cancer cells are cells that divide continually, forming solid tumors or flooding the blood with abnormal cells. Cell division is a normal process used by the body for growth and repair.

Cell Growth: Understanding Nature’s Architect of Life for People in a Hurry.


Cell growth is an intricate process where cells accumulate mass and increase in physical size. It is the cornerstone of biology, essential for multicellular organisms to develop and maintain life. From the tiniest red blood cells, measuring a mere 5μm in diameter, to the sprawling motor neurons spanning hundreds of micrometers, cell growth shapes life as we know it. In this article, we will explore the mechanisms of cell growth, its critical role in various biological contexts, and how its deregulation can affect cancer research.

Diversity of Cell Sizes

Cell growth leads to diverse cell sizes. On average, animal cells have diameters ranging from 10 to 20 μm, but this range is just the tip of the iceberg. The diversity spans from the diminutive red blood cells to the impressive motor neurons. Red blood cells, responsible for oxygen transport in the body, are among the smallest cells at around 5μm in diameter. In stark contrast, motor neurons, vital for transmitting signals in the nervous system, can extend hundreds of micrometers in length, showcasing the incredible variability of cell sizes.

Water takes up approximately 70% of a cell’s weight, leaving the remaining 30% comprising macromolecules such as nucleic acids, proteins, polysaccharides, and lipids. Among these, proteins hold a prominent position, constituting roughly 18% of the total cell weight on average. This intricate balance of cellular components highlights the precision and complexity inherent in cell growth.

Factors that Influence Cell Size

Several physical and biological factors affect cell size. Any disruption in the finely tuned cellular processes controlling biomass accumulation can contribute to cancer development.

In some cases, cell size is directly proportional to DNA content. Endoreplication: where DNA replication proceeds without subsequent cell division, leading to increased cell size. A classic example is in megakaryoblasts, the precursors to platelet-producing cells in bone marrow. These cells cease dividing and undergo multiple rounds of DNA synthesis, increasing their size. However, it remains an enigma whether this increase in DNA content directly causes an increase in total cellular material or if cells actively adjust their growth to accommodate the larger genome size.

Strategies of Growth in Nature

Nature employs diverse strategies for cell growth. They occur in animals, plants, and single-celled organisms. For instance, adipocytes can expand their size significantly, reaching dimensions of 85 to 120 μm, through the accumulation of intracellular lipids. This process stands in contrast to endoreplication.

On the other hand, terminally differentiated cells such as neurons and cardiac muscle cells cease dividing while still growing. These cells increase their macromolecule content in direct proportion to their specialized functions, finely balancing extracellular cues from nutrients and growth factors with intracellular signaling networks responsible for cellular energy and macromolecular synthesis.

Cell Growth in Dividing Cells

Cell growth is highly regulated and distinct from cell division, although the two processes are intricately linked. To maintain a consistent average cell size, dividing cells must grow with each passage through the cell division cycle. Typically, growth occurs during the G1 phase of the cell cycle, closely coordinated with DNA synthesis (S-phase) and mitosis (M-phase).

Once a cell reaches a threshold size, cells may commit irreversibly to at least one round of division, making adequate size a prerequisite for DNA synthesis and mitosis.

Measuring Cell Growth

Measuring cell growth is a scientific challenge that involves assessing factors such as metabolic activity and membrane integrity. Various techniques exist, such as tracking dyes that bind to cell membranes or intracellular proteins. These dyes can provide insights into cell growth, albeit they also have limitations, including the potential for cell damage and the requirement for specific incubation periods.

In cases where one cannot detect cell growth due to cell damage, nutritional demands, or slow growth rates, assessing metabolic activity becomes a valuable alternative.

Impact of Microenvironment

The microenvironment in which the cell resides profoundly influences cell growth and migration. The extracellular matrix (ECM) offers structural support, guidance cues, and a regulatory framework for intercellular communication.

The ECM consists primarily of structural proteins such as collagens, elastin, and proteoglycans. It provides structural integrity, regulates cell behavior, and is crucial in embryonic development, tissue repair, and wound healing. In specific organs like the urinary bladder and kidney, the native ECM’s composition and architecture dictate development, function, and protection.


Cell growth is a remarkable and indispensable aspect of life, often overlooked but holding the key to understanding complex biological processes and diseases, such as cancer. Whether we are pondering the incredible adaptability of cells employing diverse growth strategies or the precision with which dividing cells manage their size, c. growth remains a captivating journey into the heart of life’s mysteries.

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MBChB (MUK), Graduate Fellow, Department of Physiology, Makerere University Founder and Content Creator Peer reviewer, Associate Editor

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