Download Modern cell theory

Modern cell theory
Modern biologists have made certain additions
to the original cell theory which now states that
1. All organisms are made up of cells.
2. New cells are always produced from preexisting cells.
3. The cell is a structural and functional unit of
all living things.
4. The cell contains hereditary information
which is passed on from cell to cell during cell
division.
5. All cells are basically the same in chemical
composition and metabolic activities.
As the cells of different parts of an organism
(such as epithelial cell, muscle cell, nerve cell,
etc). vary in shape, size and internal structure, no
cell can be described as a typical one. In spite of
all these variations, they are all cells, showing
certain common fundamental properties.
Plant cell
Eukaryote v Prokaryote
Eukaryote—Eu means true or real. This is what
we mean when we talk about a cell.
organelles
Example Animal and plant cells
Has
Prokaryote- Pro means first or old or ancient
cells. NO organelles
Example Bacteria.
Organelles – defined as little organs
Examples of organelles:
1 nucleus
2 mitochondria
3 cytoplasm
4 cell membrane
5 vacuole
6 Chloroplast
7 Ribosomes
8 ER endoplasmic reticulum 2 types smooth,
rough
9 Golgi, Golgi body, or Golgi complex, or the
Golgi apparatus
Types of Microscopes
3 types that we use today
1 Compound light uses 2 lens
2
TEM Transmission Electron
Microscope invented in the 1950
Uses electrons for its energy source.
Electrons are negatively charged particles
that make bonds in chemical rxns.
The specimen must be dead; it uses a
vacuum for placing the specimen. The
vacuum is to prevent air from disturbing
the movement of the electrons.
3 SEM Scanning Electron Microscope
Structure of cell
Both prokaryotic and eukaryotic cells possess the
basic features of a plasma membrane and
cytoplasm. The plasma membrane is the outermost
surface of the cell which separates the cell from the
environment. The cytoplasm is the aqueous content
within the plasma membrane.
Plasma membrane : It is like any other membrane
in the cell but it plays a very important function. It
forms the border of a cell, so it is also called the
cell membrane. It is primarily composed of proteins
and phosphalipid. The phospholipids occur in two
layers referred to as a bilayer. Protein is embedded
within the lipid layer, or attached to the surface of
it. The plasma membrane is elastic and very fluid
because of protein and lipid. Normally the function
of the plasma membrane is that of a gate-keeper. It
allows certain important substances to enter and
exit the cell.
Cytoplasm and organelles : The cytoplasm is a
semi-solid substance which is present in the cell
and which gives structure, size, shape and
foundation to the cell. It is enclosed by the plasma
membrane. Within the cytoplasm are a number of
microscopic bodies called organelles that perform
various functions essential for the survival of the
cell.
Endoplasmic reticulum with the nucleus and the Golgi complex
Endoplasmic reticulum (ER) : is one of the
important organelles present in the cytoplasm.
Endoplasmic reticulum is a series of membranes
which extend throughout the cytoplasm in
eukaryotic cells. In certain cases in ER there are
submicroscopic bodies called ribosomes which are
involved in production of protiens.
Rough ER : In this kind of ER the ribosomes are
presenton the surface.The endoplasmic reticulum is
responsible for protein synthesis in a cell.
Ribosomes are suborganelles in which the amino
acids are actually bound together to form proteins.
There are spaces within the folds of ER membrane
are known as cisternae.
Smooth ER : This type of ER does not have
ribosomes.
Another organelle is the Golgi body or Golgi
apparatus (G.A.). The Golgi body is a series of
flattened sacs usually curled at the edges. Proteins
which have formed in ER are processed in G.A.
After processing, the final product is discharged
form the G.A. At this time the G.A. bulges and
breaks away to form a dropline vesicle known as
secretory vesicles. The vesicles move butward to
the cell membrane and either insert their protien
contents in the membrane, or release their contents
outside the cell.
There is another organelle which is related to the
Golgi apparatus called the lysosome. The lysosome
is derived from the Golgi body. It is a sac of
enzymes in the cytoplasm, used for digestion
within the cell. These enzymes break down
particles of food taken into the cell and make the
food product available for use. There are also
cytoplasmic organelles called peroxisomes in the
cell which produces the enzymes to degrade fat
molecules.
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