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Cells Size and Scale and Number

Around us, in the millions, are other forms of life. There is considerable variation in the size and form of each one. Their organs are also not all the same in terms of size, form, or cellular makeup. Let’s discuss more, cells size and scale and number in different organisms.

Cells Count

Trillions of cells make up the human body. Each of these cells, surprisingly, has its own unique shape and size. A wide variety of cell types carry out a wide variety of tasks. A multi-cellular organism is any living thing with more than one cell. A fertilised egg, the first cell of any creature. The number of cells in the developing organism increases as this fertilised egg divides and multiplies. A unicellular organism is one that consists of only one kind of cell.

A unicellular organism is fully capable of carrying out all the essential life processes. That’s right; just like multicellular organisms, single-celled ones carry out their tasks, even with just a single cell. Single-celled organisms, like amoebae, are capable of capturing food, digesting it, breathing, releasing waste, expanding, and reproducing. In multicellular organisms, the same kinds of jobs are done. But in their case, these jobs are done by a group of specialised cells that come together to form different tissues. In turn, these tissues grow into organs.

Cells Shape

Most of the time, the cells are round, long, or round. There are also long cells that are pointed at both ends. These cells have a shape like a spindle. There are times when the cells are very long. Some may have more than one branch, like the neuron or nerve cell. Messages are sent and received by the nerve cell.

So, it helps make sure that all the parts of the body work together and in the right way. A membrane holds the parts of the cell together. Animal and plant cells get their shape from this membrane. There is a wall around their cells. The cell wall is an extra layer that goes on top of the cell membrane. It gives the cells strength and shape.

cell shapes and sizes

Figure 1: Cell shapes and sizes. Source: www.geeksforgeeks.org

Cells Scale

Diameters of eukaryotic cells range from 10 to 100 µm, while prokaryotic cells are just 0.1 to 5.0 µm in size. Due to their compact size, prokaryotes efficiently distribute incoming ions and organic molecules throughout the cell. Likewise, prokaryotic cells are quite good in dispersing their waste products. This is not the case in eukaryotic cells, which have developed various structural modifications to facilitate intracellular transport. Here are some example of relative sizes of biological materials

Eukaryotic cell (plant) = ~100 μm

Eukaryotic cell (animal) = ~10 – 50 μm

Organelle (e.g. mitochondrion) = ~1 – 10 μm

Prokaryotic cell (bacteria) = ~1 – 5 μm

Virus = ~100 nm

Plasma membrane = ~7.5 nm

Molecules (e.g. glucose) = ~1 nm

Atoms = ~100 pm

cell scale diagram
cell scale diagram

Figure 2: Cell scale diagram

FAQ

FAQs on Cells Size and Scale and Number

Actin filaments (red) and microtubules (green) are two types of proteins that give cells their structure.

The factors limiting the size of cells include: Surface area to volume ratio and Nucleo-cytoplasmic ratio.

A growing cell’s volume increases while its surface area stays the same. Therefore, there is less area available for material transfer within the cells.

Most cells in animals and plants are between 0.01 and 0.10 mm long. About 0.05 mm is the smallest thing that can be seen with the naked eye. To get a good look at any cell, we need a microscope. The micrometre, written as μm, is the best way to measure most cells.

Eukaryotic cell (plant) = ~100 μm

Eukaryotic cell (animal) = ~10 – 50 μm

Organelle (e.g. mitochondrion) = ~1 – 10 μm

Prokaryotic cell (bacteria) = ~1 – 5 μm

Virus = ~100 nm

Plasma membrane = ~7.5 nm

Molecules (e.g. glucose) = ~1 nm

Atoms = ~100 pm