why are cells so small

why are cells so small?

Firstly, what is a ” Cell”?

Cells are single units of living organisms, in which substances can enter and leave the cell at will. Three things make up a cell: the cell membrane, the nucleus, and its contents.

Within each cell is a structure that contains the nucleolus, which contains most of the DNA and the nucleolus, as well as the cell membrane, which controls substances entering and leaving the cell.

Cellular fluid, the cytoplasm is also where most RNA is made. The Golgi compound, mitochondria, and endoplasmic reticulum are also part of the cytoplasm, which also contains other small parts that perform specific functions.

More than 30 billion cells are found in the human body, and the cytoplasm is where most chemical reactions occur.


Cells are so small that you need a microscope to examine them. Why?

To answer this question, we need to understand that cells interact constantly with their surrounding environment.

It takes a microscope to view the vast majority of cells in your body as well as bacteria cells that are too small to see without the aid of a microscope. Cells that grow too big stop growing and divide.

A human cell is typically 10 to 20 micrometers in diameter. Our visual threshold is approximately 100 um. Our bodies could be up to 10 times wider and taller than they are today.

In animals, often, the diameter of a cell is ten microns (10 millionths of a meter). Larger cells, like the egg cells of African clawed frogs, can be one millimeter across, but such large cells are not common.

For materials, including oxygen and glucose, to pass between cells and their environment efficiently, the cell membrane must be able to do so. If the membrane cannot do this, the cell can die.

The largest human cell type is the egg. The smallest is the fat cell. The largest type is the bone marrow cell (megakaryocyte), which delivers the blood platelets.

The length of some skeletal muscle cells exceeds 30 cm, and the length of some nerve cells can reach 150 cm. However, these cells are too small to observe without magnification.

Depending on their function: 

Water is necessary for respiration, as well as absorbing gases and food molecules, and eliminating wastes. For most cells, this occurs at the plasma membrane.

As a cell grows, its internal volume increases, and the cell membrane also expands. Part of the cell surface has to be allocated to each internal region.

However, the volume of cells increases more quickly than their surface area and, as a result, the surface area available for materials to pass through the cell decreases concerning the volume.

When just enough surface remains to service the interior, the growth of the cell will stop, ensuring its survival.

A cell can no longer function if it does not divide into smaller cells or if its surface area/volume ratio is not favorable.

Depending on Size:

Small cells make metabolic movements easier. Just like on smaller utensils, and the nucleus is also capable of controlling cytoplasmic processes.

Smaller cells have a better ratio of surface to volume, allowing them to move more molecules and ions per unit of cytoplasmic volume. This allows them to have a larger distribution of ions and molecules.

As cells grow, their surface area to volume ratio decreases. Indicating that the nutrient delivery system and waste removal system must both work efficiently.

Thus, once the cell has grown past a certain point, not enough material is going to be capable of crossing the membrane quickly enough, To support the increased cellular volume. That is why cells are so small.

Depending on the volume:

The cell size helps increase the efficiency of the cell’s waste expulsion. Also, it helps absorption processes. Meaning their surface area and volume are proportional to each other.

Additionally, since the nucleus of the cell is small, communication to other organelles is fast, allowing for efficient regulation while the conditions for diffusion are still ideal.

A cell’s size is since it needs to have an easy time diffusing through materials. A cell membrane needs to allow easy passage of materials inside and outside of the cell, which makes it harder and slower for materials to pass through the cell membrane.

Compared to a few big objects, a lot of small objects have a larger surface area concerning their volume, which is why cells are so small. This is because the surface area of small objects is much larger than that of large ones.

Having fewer cells means they will have a greater chance of replicating when damaged. The membrane of a cell will not be able to accommodate the inside of the cell if the cell grows beyond a certain size. Hence, when a cell becomes too large, it will divide into smaller cells to maintain a surface area/volume ratio more favorable to its proper functioning. As a result, cells remain small so that they can survive.

What happens if a cell grows too big?

If a cell grows too big, it will eventually die. Conversely, if a cell’s volume to surface ratio is too high and the cell is small, the diffusion pathways will not be able to remove heat quickly, which leads to cell death.

The small size of cells has a number of benefits. What are three reasons for it?

Despite the small size of cells, they have a high ratio of surface area to volume, so molecules and ions can move more easily across the cell membrane.

When a cell is large, what three problems does it encounter?

The cell’s volume increases faster than its surface area with increasing size, causing a decrease in the ratio of surface area to volume of the cell and making it more difficult to transport waste products out of the cell.

Additional Information:

  • There are single-celled organisms in In prokaryotes. While in eukaryotes, they are either multicellular or single-celled. Eukaryotes have a nucleus, while prokaryotes do not.
  • All organisms have a basic structural, biological, and functional unit called a cell, which is Latin for “small room”. Cells are often referred to as “the building blocks of life.”.
  • There are about 10 micrometers of Mycoplasma cells that are similar to Pleuropneumonia.
  • An ostrich’s ovum is the most valuable cell in its body.
  • A cell kind is a classification that distinguishes morphologically and phenotypically distinct cells within a species.
  •  The largest type of cell in the human body: female ovum