Why are cells big and small? Top journal reveals the microscopic world of cells

Li ChuanfuHuang Ting

In the vast field of biology, as the basic unit of life, cell size and morphology have always been a hot topic for scientists. So, what determines the size of a cell? The answer to this question is far more complicated than we think. Recently, Cell, a world-class journal in the field of biology, published a paper that explored the factors that affect cell size from multiple perspectives, further revealing the microscopic world of cells.

Cell size usually refers to the volume of the cell, which can be estimated by measuring the diameter and height of the cell. The sizes of different types of cells vary greatly. Bacterial cells are only about one or two microns, while ostrich egg cells can reach a diameter of 5 centimeters, making them one of the largest cells. From tiny bacterial cells to huge egg cells, the volume can differ by tens of thousands of times. In addition, within the same multicellular organism, there are also huge differences in cell size. For example, in the simple multicellular organism Caenorhabditis elegans, cell size differences can span two orders of magnitude.

Cell size is largely determined by genetics. Genes affect cell growth and division by controlling the progression of the cell cycle. Specific genes can encode proteins that regulate cell size. These proteins can control the synthesis and breakdown of substances within the cell, thereby affecting cell volume.

The accumulation of intracellular substances is also a key factor in determining cell size. Cells gradually increase their volume by synthesizing biomacromolecules such as proteins, lipids, and carbohydrates, as well as absorbing external nutrients. The accumulation rate and efficiency of intracellular substances directly affect the growth rate and final size of cells.

The living environment of cells also has a significant impact on their size. The supply of nutrients, oxygen concentration, temperature, pH and other environmental factors will affect the growth rate and metabolic activity of cells. Under suitable environmental conditions, cells can grow and divide more efficiently, thus forming larger cells.

Cells do not exist in isolation; they communicate and interact with each other through signaling molecules. These interactions between cells can regulate cell growth, differentiation, and apoptosis, thereby affecting cell size. For example, some signaling molecules can promote cell growth, while others may inhibit cell growth.

The size of a cell is closely related to its function. In multicellular organisms, different types of cells undertake different physiological functions, which requires them to have specific sizes and shapes. For example, muscle cells need to be large to generate force, while nerve cells need to be slender to transmit signals.

From an evolutionary perspective, the diversity of cell size is the result of biological adaptation to the environment. Under different living conditions, cells of different sizes may have different survival advantages. For example, in an environment with scarce resources, smaller cells may find it easier to obtain sufficient nutrients, thereby increasing survival rates.
For proliferating cells, when the cells grow to a certain size, they will divide. At present, there are two views on this process: one view is that cell growth is a continuous process and is not affected by the starting size. Cells increase a constant growth amount in each cycle until the conditions for division are reached. This process ensures that cell growth has a certain regularity and predictability. Another view is that cell growth is a dynamic process that adjusts the growth rate according to the current size. There is a "size sensor" inside the cell that monitors the volume of the cell and sends a division signal when it reaches a critical size. This process ensures that the cell does not divide too early or too late, maintaining the stability of the cell size.

With the development of science and technology, modern biologists have been able to precisely control cell size through gene editing, cell engineering, etc. These technologies have broad application prospects in the fields of medicine, biopharmaceuticals, etc., and can promote tissue repair and regeneration by regulating the size of stem cells.

The study of cell size not only helps us understand the nature of life, but also provides new perspectives for disease treatment and health maintenance. With the deepening of research, we are expected to reveal more about the mechanisms of cell size regulation and make more contributions to improving human health and the development of biotechnology.

(The author Li Chuanfu is an engineer at the Green Energy Industrial Research Center of Huazhong University of Science and Technology and a member of the Royal Society of Chemistry. Huang Ting is a master's student at Huazhong University of Science and Technology)