All living things are made up of cells” – a fact that was brought to our notice as part of our basic science education in the lower grades. Some living organisms are made of a single cell, (right, we remember that part where they introduced us to ‘amoeba’) and some living organisms are made up of thousands of cells. (…right, we remember that part too! It was right after that we dozed off to sleep) As much as it would be difficult to imagine human beings as a package formed by a union of millions of cells, 37 trillion to be more precise, that is what we are!
Now for all those facts that you missed in science class and more, read on…(hopefully, you will stay awake this time around!)
‘Cells’ – that name was assigned to it by its discoverer, an English man, Robert Hooke. And how did he discover it? When he was experimenting with a new instrument called the microscope! He was viewing a slice of cork and realized that it was made up of several tiny boxes, which reminded him of the “cells” monks lived in; and so the name.
According to scientists, the first known cells originated on our planet some 3.8 billion years ago! Of course, they started off as single-celled organisms known as ‘prokaryotes’. And what is special about them – they don’t have a nucleus or any other internal structure! Doesn’t make sense? Think of bacteria; they are prokaryotes.
There are different kinds of cells. It has been estimated that the human body alone is organized by over 200 different types of cells! And each of these cells performs different functions.
However, cells are themselves classified into two major groups – prokaryotes, we just read about them, and eukaryotes. Eukaryotes are found in some single-celled organisms, fungi, plants, animals, and of course, humans. They contain complex internal structures or nucleus, called organelles. And this is what contains our DNA.
Generally, all cells are in the range of 0.001 to 0.003 cm in diameter. In other words, they are invisible to the naked eye. However, there are exceptions! Some nerve cells can stretch from our toes to our hip bones, or vice-versa, in order to transmit electrical signals through our body.
Did you know that the average adult typically carries around 3 to 5 pounds of bacteria! (Aha! Now that explains why our weight-loss measures are ineffective) but, they are so much tinier than are cells that they don’t contribute to our body mass! Really?! They account for less than 3 percent of our body mass!
Cells are living organisms; therefore, they have a birth and death. Different cells have different life spans. The human red blood cell has an approximate lifespan of 120 days.
On an average, around 50 to 70 billion cells die in the human body! Mortality rate is high in our skin cells, blood cells, and cells that line our organs and glands. That explains the emphasis on a protein-rich diet, need to rejuvenate our skin, and consume lots of fruits and veggies.
Cells follow a policy of ‘divide and rule’ – yes, they produce new cells by division of a single cell into two; also known as mitosis. There is also another process called meiosis, where one cell creates four new cells with distinct genetic framework. The latter is limited to very few cells, like those that create eggs and sperms.
Stem cell is one term that has garnered a lot of interest in recent times; and there is a valid reason for that. These cells are capable of growing into any type of cell in our body. In other words, they are capable of growing into any organ or part in our body!