Health - Biology
By: - at June 9, 2013

An Introduction to the Cells of Organisms

Cells of organisms have been studied for hundreds of years. Organisms are entirely made up of cells, thus making it a worldwide unit of life. An organism is any living thing, whether it is a plant, an animal or fungi. Some organisms (known as simple organisms) are composed of only one cell; others are composed of many more. These are multicellular organisms, human beings being one example. The first cells to ever be studied closely were those belonging to plants and animals. Cell of an organism

How do we know that organisms are composed of cells?
We know that organisms are composed of cells due to discoveries made possible through the use of microscopes. The first microscope used to study cells was a light microscope, however it was soon discovered that much better results were to come from electron microscopes; they are able to magnify at least 1000 times more!

It was Robert Hooke in 1665 who first described cells, but it wasn’t until 1838 – 1839 (Schleiein and Schwann) that the cell theory came about. The cell theory is the basic unit of structure and function of the cell; the key components. In 1855, Rudolf Virchow discovered that new cells can arise from pre-existing cells through cell division. Cell division is the process that creates new cells, making reproduction of life possible, as well as the repair and growth of cells.

Electron Microscope:
Electron Microscope

Plant and animal cells: differences and similarities
There are some similarities between plant and animal cells, one of which is that they both have a plasma membrane. The plasma membrane is the cell ‘barrier’. It is composed of lipids (fats and oils) and effectively controls what goes in and what leaves the cell. They also both contain organelles, which are distinct structures within a cell, as well as a nucleus. The nucleus is an organelle and contains all the genetic material of the cell (otherwise known as DNA). It controls growth, reproduction and metabolism. It is essentially the chemical control center of the cell. As well as these similarities, they also both have what is known as mitochondria. Here, fuel molecules are broken down to obtain energy (or ATP) through aerobic respiration. This means to use oxygen during the process of getting energy. Although most animal and plant cells use aerobic respiration, certain types use anaerobic respiration which means to obtain energy without the use of oxygen. This isn’t very efficient. Some fundamental differences between animal and plant cells are as follows; plant cells have a cell wall. The cell walls of plant cells are made up of complex carbohydrates. They also contain chloroplasts, which are responsible for the green coloring of plants. As well as this, they also have a sap vacuole which helps to hold the plant straight and keep it up right. Some features in animal cells that aren’t found in plant cells are; centrioles, cilia, and flagella. Cilia are an extension of the cells cytoplasm, while flagella help to move the cell from place to place.

Plant and Animal cell Differences:

Plant and Animal cell Differences

Cell classification
When study of cells first began, biologists first classified cells as either ‘animal’ cells or ‘plant’ cells. However, it was soon realized that bacteria and fungi do not fit this classification. Biologists now recognize two kinds of cell organisms, classified as to what kind of cell they are composed of. The first kind of cell that biologists can identify is prokaryotes; these cells have no nucleus, which means that the DNA is effectively ‘naked’ and unprotected inside the cytoplasm. The ‘pro’ part of the term means ‘before’, as these kinds of cells were believed to have eventually evolved into the second type of cell. These types of cells are thought to be the first kinds of cells on Earth! All bacteria belongs in this group. The second group of cells that Biologists identify are Eukaryotes. These cells have a nucleus where the entire DNA is safely contained, and it belongs to animals, plants, fungi, and single celled organisms.

The study of cells is a fascinating world that has been studied extensively, meaning that there is a wealth of information available for those who want to know more.





An Introduction to the Cells of Organisms
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