Ok.. It was the first week of class and we discussed and learnt about CELLS.
Firstly, WHAT IS A CELL?? Well as our Hokage correctly stated a cell is the smallest unit that is able of performing live function :
- Stimulus Response
History Time: The cell was discovered by a guy named Robert Hooke in 1665. His breakthrough changed science forever. He discovered the cell, by examining a very thin slice of cork under a coarse, compound microscope and saw millions of tiny pores which he said reminded him of the wall like compartments a monk would live in. Because of that small linkage in his thoughts he decided to call them “cells.“In later years a guy named Anton van Leeuwenhoek was the first man to witness a live cell under a microscope, in 1674 described the algae Spirogyra and named the moving organisms animalcules, meaning “little animals”. Along with Matthias Jakob Schleiden, Theodor Schwann, Rudolf Virchow and Others led to the development of the Cell Theory.
The Cell Theory states:
- All Living Organisms are composed of cells. They may be Unicellular of Multicellular.
- The Cell is a basic unit of life.
- Cells arise from preexisting living cells.
There are two general categories of cells:
Prokaryotic generally means “Before The Nucleus”. As the name suggest these cells do not contain a nucleus. This is a simple cell. There are two kinds of prokaryotes Bacteria and Archaea. A prokaryotic cell has three architectural regions:
- Flagella and pili ( not present in all prokaryotes)
- Cell Envelope
- Cytoplasmic Region [contains cell Genome (DNA) and ribosomes]
Eukaryotic basically means “True Nucleus”. Just as the name states these cells have a nucleus. These cells are approximately 15X wider than a typical prokaryotic cell. Fungi, Protozoa, Plants, Animals, Slime Moulds and Algae are all eukaryotic.
Above is a typical comparison between a Prokaryotic and Eukaryotic cell. As seen the Eukaryotic cell is 10X the size of the Porkaryotic cell. In the Diagram, it is shown that there are many similarities between the cells such as;
- Plasma Membrane
After looking at the Image above you may be wondering does it have a limit to how small a cell can get or how big it can get? Well THERE IS.
The Limit as to how small a cell can be is based on the amount of DNA that is needed to make the enzymes necessary for life.
The Limit as to how large a cell can become is based on the Surface Area to Volume Ratio. Simplified it states that as the surface area of the cell increases the Volume of that cell also increases exponentially, so much that it slows down the rate of diffusion. Thus, the cell cannot get rid of its waste fast enough or get nutrients fast enough therefore the cell will either be poisoned because of the waste or starve because a lack of nutrients.