IMPORTANT CONCEPTS
The modern cell theory
By schwann in 1839 , cell theory had two
basic principles:
1. All organisms consist of one or more
cells.
2. The cell is the basic unit of structure for
all organisms.:
The third principle of the modern cell theory by
Rudolf Virchow in 1855 :
3. All cells arise only from preexisting cells.
Units of measurement in cell biology
The micrometer (μm) sometimes also called a micron) is
one millionth of a meter is the most useful unit for
expressing the size of cells .
The nanometer (nm)
for molecules and subcellular structures that are too small
to be seen with the light microscope .
nanometer is one-billionth of a meter
Angstrom (Å), is
used in cell biology when measuring dimensions
within proteins and DNA molecules. An angstrom equals
0.1 nm,
which is about the size of a hydrogen atom.
Date 2-2-2014
First lecture
The Emergence of Modern
Cell Biology
Modern cell biology results from introducing together of
three different strands :
1- Cytology
2- Biochemistry
3- Genetics
Look to the FIGURE 1-2 The Cell Biology Time Line that I
submit it to you
The Cytological Strand
The light microscope has allowed us to visualize
individual cells, which are approximately 1-50 µm
in size. Historically, its limited resolving power did
not allow us to see details of
structure smaller than about 0.2 µm (200 nm), but
modern light microscopes are surpassing that
limit.
.
The Cytological Strand
Several types of light microscopes allow us to view
preserved or living specimens at magnifications of
about 1000X These include brightfield, phasecontrast, differential interference contrast,
fluorescence, confocal, and digital video
microscopes, each of which offers particular
advantages in studying and understanding cells.
The Biochemical Strand
- Discoveries in biochemistry have revealed how many of the
chemical processes in cells are carried out, greatly
expanding our knowledge of how cells function.
-Major discoveries in biochemistry were the identification of
enzymes as biological catalysts, and
the discovery of adenosine triphosphate (ATP)
The Biochemical Strand
Several important biochemical techniques that have allowed
us to understand cell structure and function are
- subcellular fractionation,
- ultracentrifugation,
- chromatography,
- electrophoresis,
- mass spectrometry
The Genetic Strand
- The chromosome theory of heredity states that the characteristics
of organisms passed down from generation to generation
result from the inheritance of chromosomes carrying discrete
physical units known as genes.
-Each gene is a specific sequence of DNA that contains the information to
direct the synthesis of one cellular protein.
-DNA itself is a double helix of complementary strands held together by precise
base pairing. This structure allows the DNA to be accurately duplicated as it
is passed down to successive generations.