Unit 1 : Introduction to the cell
This unit introduces how the cell works. The historical aspects of cell biology, and how it was invented.
It talks about how a typical cell works, and how they are classified ( prokaryotes or eukaryotes).
The first microscope was invented by Robert Hooke, in the 1970's. He used the microscope to observe
pieces or cork, in which he saw little rooms, or cellula's. This is where the word cell comes from, because
in the corks, the cellua, were the spaces that made up the cell.
Another man improved on Robert Hook's model of a microscope. Robert Hook made the microscope but
Anthony Leeuwenhoek, at about the same time, improved on his invention. He was able to make a
microscope more clear by improving the quality of the lens. This made magnifications like 300x,
possible. Therefore he is often called the father of microbbiology. Anthony Leeuwenhoek, using his
imrpoved model of the microscope was able to see ogranisms that were single celled. For instance, he
observed the bacteria from his own mouth. He called these animalcules. He saw things like blood cells,
There was stalled process after Anthony Leevanhoek's discovery as no one really found anything new.
However, after the 1800's, they created a new thing, the compound microscope. The compound
microscope had improved magnification and resolution. It was able to see more, and in more detail. A
person would be able to see things less than 1 um.
Microscopes aid in being the able to see thing. Humans are able to see some cells with the human eye,
but anything smaller than that, such as things inside a cell, we can't see. Atoms are the smallest unit of
life. They are about 0.2 nm. This is very tiny, and can only be seen by an ELECTRON microscope. The
sizes increase by x10 as we get to bigger things like molecules, and organelles. Therefore it goes from
0.2nm, to 2 nm, to 20 nm, and etc. Light microscopes are able to see up to 200nm. From this, they can
Light Microscopy, or cytology can be used to observe different organelles. When you stain a sample, you
make it so that the image is very vividly colored. Fluorescence Microscopy is when you use florescent
light to stain the samples so you get really pretty and colourful flourescent images.
Electron Microscopy, is when you can observe into more detail. For instance, in scanning or
transmissions. There are two types SEM and TEM, where TEM is a cross section diagram.
People are now able to see things as small as 0.2 nm atoms with electron microscopes. From this, they
can start developing theories about what a cell is. This all started with Robert Hooke, and him analyzing
this own blood/sperm/saliva and etc…
The beginning of the cell theory started in 1800's with different botanists and zoologists, who observed
cells of plants and animals. His name was Robert Brown. He observed different plants, and he saw that
every plant had a round structure inside it. This round structure was called the nucleus. Robert Brown was the first one to observe the nucleus of a cell by observing plants. Then Matthias Schleiden, who also
looked at plants saw that all plant tissues were made up of cell. Therefore he deducted that all plants
were made from one baby cell, an embryotic cell. A zoologist was able to find the same findings in
animal cells. He saw how simular plants and animals were.
Schwann made the cell theory. In the theory, all organisms are made up of cells, and the cell is the basic
unit of structure for one or more organism. He also added that all cells arise only from pre-existing cells.
Schwann developed the cell theory which states that cells are the basic unit of life. Aspects of what
constitutes as a theory are discussed. There is a difference between a scientific fact, and a theory.
The scientific method, is what most scientists use to find a scientific fact. A fact is something that is
absolutely true. A scientific fact is when we try our best to explain something based on observations and
experiments. However, as change is constant ,things are always being replaced with newer, better,
models. The scientific method is when you make observations, a hypothesis, and experiments.
A theory is when something is tested using the scientific method. It has been tested so many times, that
it is almost known as true. Theories make up the "solid ground" of science. When these theories create
such a solid ground, that it creates a foundation in science, they are known as laws.
There are different strands of cell biology. There are many properties of a cell. They are really complex and organized. They go from atoms, to
molecules, to macromolecules, to organelles. This is all enclosed in a plasma membrane. Cells are able
to reproduce and multiply. They also use energy to carry out metabolic reactions. Most of their
processes occur at molecular levels, because they are so small. They engage in mechanical movements
of substances with in the cell, they react with external stimuli, and are self regulated.
There are two classes of cells, prokayotics and eukaryotics. Prokaryoic cells are very simple. They do not
have a nucleus and can