Transcript Cell Theory and the Cell

Cell Theory &
Cellular Structures
The Discovery of Cells
Term “cell” was coined
in 1665 by Robert
Hooke when he looked
at a slice of dried cork.
He observed that the
cells looked like little
rooms and named them
boxes. He also looked at
the cells of living plants
and found that some of
them were filled with
liquid.
Hooke also looked at
the eyes of house flies,
feathers and fish scales.
But he spent most of
his time studying plant
cells. Plant cells have
cell walls and are easy
to see. Animal cells do
not have cell walls,
which makes seeing the
outline of these cells
more difficult.
Anton van Leeuwenhoek
This man was a Dutch merchant
and made his own microscopes to
view pond scum. He discovered
small organisms in the water and
gave them the name of
“animalcules.”
Today these single cell organisms
are called protists. Leeuwenhoek
also looked at animal blood and
found some major differences. He
was also the first person to view
bacteria
Cell Theory
1. All living things are comprised of cells.
2. Cells are the smallest “living” unit in an
organisms.
3. All cells come from existing cells.
Cell Diversity
• Lots of shapes and sizes
Typical Cell
Cell Organization
Two Kinds of Cells
There are two basic types of cells:
1. cells with a nucleus
2. cells without a nucleus
Eukaryotic Cells: cells with a nucleus
Prokaryotic Cells: cells without a nucleus
Prokaryotes
Prokaryotes are single celled organisms that do not have a nucleus.
Yet, they still have DNA. This DNA is a long, circular molecule and
is shaped like a rubber band. These cells also do not have membranebound organelles. They have strong web like cell walls and most
prokaryotes are either bacteria or Achaea (an ancient bacteria).
Eukaryotes
Eukaryotes are the largest cells and are about 10 times as large as
most prokaryote cells. These cells have a nucleus which holds the
cell’s DNA. These cells have organelles that have specific job
functions. Plants and animals have eukaryotic cells.
The Parts of the Cell
•
The cell includes two basic parts:
1.
2.
3.
Cell Membrane: is a protective layer that covers the cell’s
surface and acts as a barrier.
The membrane also controls materials going into and out of the
cell.
Cell fluid is called cytoplasm
• Cytosol (fluid portion of the cytoplasm)
• Organelles: carry out the processes of life, have specific
structures
Cell Membrane
•
•
•
•
Outer boundary
Physical
Chemical
Comprised of two layers of lipid (fat)
– Outer and inner layers
• Proteins
• Proteins give the cell its unique
“personality” or function
Cell Membrane
Function of Membrane Proteins
1.
2.
3.
4.
Transport (in and out of cell)
Receptors
Cell adhesion
Cell recognition
Cell Organization
Cytoplasm
•
1.
2.
Is comprised
of:
Cytosol (fluid
portion of the
cytoplasm)
Organelles
(cell “organs”
or functional
parts)
Cytosol
• Intracellular fluid
• Contains dissolved nutrients, ions, proteins
and waste products
Organelles
1. Endoplasmic reticulum (ER)
• A network of membrane-bound tunnels
throughout the cytoplasm
Endoplasmic Reticulum
Rough ER
Smooth ER
Golgi Apparatus
• Flattened membranes
• Involved in packaging and secretion of
proteins
Golgi Complex
The Golgi Complex
packages and distributes
proteins.
The complex looks like
a smooth ER. Lipids
and proteins from the
ER are delivered to the
Golgi, and they are then
modified to do different
jobs. The final products
are then packaged into
vesicles and transported
to other parts of the cell.
Mitochondria
• Inner membrane folded into cristae
• Adenosine triphosphate (ATP) produced
on cristae.
• ATP is high energy compound.
• ATP only produced in mitochondria.
Nucleus
Nucleus
All cells have DNA
(deoxyribonucleic acid). DNA
is the genetic fluid and carries
information needed to make
new cells and new organisms.
DNA is passed on from parent
cells to new cells and directs
the activities of a cell.
DNA gives cells the
instructions to make proteins
Nucleus
•
•
•
•
Control center of cell
Contains DNA/chromosomes
Genetic repository for ~ 35,000 genes
Genes control the synthesis of proteins in
each cell.
• Red blood cells don’t have a nucleus.
• Skeletal muscle cells have multiple nuclei.