Transcript Cell Theory - The Naked Science Society

Biology II - Cell Theory Review
Cell Theory
•
Term “cell” was coined in 1665 by Robert
Hooke when he looked at a slice of dried
cork. He observed that:
1. All living things are made of cells.
2. Cells are the smallest “living” unit in
an organism.
3. Cells come from previously existing
cells.
Cells - “Fundamental Unit of Life”
Prokaryotes
Eukaryotes
- single celled
- single or multicellular
- no nucleus
- no organelles
- DNA is a single,
circular molecule
- e.g., bacteria
- nucleus & nuclear
membrane
- organelles present
- DNA packaged into
chromosomes
- e.g., protozoans,
plants, animals
Cell Organization
The cell includes two basic parts:
1. Cell Membrane (outer covering of cell)
2. Cytoplasm (also made of two parts)
• Cytosol (fluid portion of the
cytoplasm)
• Organelles (organs or functional
parts)
Cell Membrane
• Includes:
– Outer boundary
– Physical & Chemical Protection
– Comprised of two layers of lipid (fat)
– Plus Layer of Proteins
– Proteins give the cell its unique
function
Cell Membrane
Organelles
Endoplasmic reticulum (ER)
• A network of tunnels throughout the cytoplasm
– for cell transport
Golgi Apparatus
• Involved in
packaging
and secretion
of proteins
• Golgi looks
like a series
of stacked
plates.
Mitochondria
• Bean shaped, with outer & inner membranes
• Cell Powerhouse – produces energy
Cytoskeleton
• Skeleton of
the cell
• Provides
structure and
shape
Plant Cell Organelles
•
Plants have three special structures not found
in animals: the chloroplast, the cell wall, and
the central vacuole.
1. The chloroplast is the site of photosynthesis,
the process of converting carbon dioxide
into sugar and oxygen using sunlight It uses
the green pigment chlorophyll to capture
the energy from light.
Plant Cell Organelles
2. Each plant cell is surrounded by a rigid cell
wall. The cell wall is outside of the cell
membrane. In woody plants, the cell walls
can become very thick and rigid.
3. Plant cells also contain a central vacuole,
which stores water. It is the storage room of
the plant cell.
Nucleus
Nucleus
• Control center of cell – “the brain”
• Contains DNA/chromosomes
• Genetic repository for ~ 35,000 genes in
humans
• Genes control the synthesis of proteins in each
cell, and hence what the cells do.
Human Red Blood Cells
Rat Muscle Cells
Next: Cell
Reproduction
Cell Cycle: life and reproduction of a cell
Part I - DNA and nuclear division (mitosis)
Part II - cytokinesis (cytoplasm duplication)
Cell Cycle: Interphase
• Before/Between mitosis
• Time of high metabolic activity
• “Normal” life of cell
Cell Cycle: Mitosis
• Process of cell division (nuclear division) which
produces daughter cells genetically identical to
the parent cell
• Four Action Phases (P-M-A-T): prophase,
metaphase, anaphase, and telophase, and then
the times between mitosis (Interphase).
• Upon completion of the phases of mitosis
(nuclear division) the cell “officially” divides
into two by a process called cytokinesis division of cytoplasm and the rest of the cell
Interphase
Not part of mitosis
Normal life of the cell
Prophase
*Chromosomes coil and condense further.
*Nuclear membrane breaks down/ disappears.
*Microtubules increase in #, spindle apparatus forms.
Chromosome duplication
Metaphase
*Nuclear membrane completely disappeared
*Chromosomes move to equator of cell & line up
*Chromosomes attach to spindle via kinetochore
Centromeric Region
Anaphase
*Movement of chromosomes via microtubules
to opposite sides of the cell. One chromatid to one
end the other Chromatid to the opposite end
Telophase
*Genetically identical at each pole
*Spindle fibers disappear
*Chromosomes uncoil
*Nuclear envelope reforms
Cytokinesis - is separate from mitosis,
= cell/division of cytoplasm.
Mitosis + Cytokinesis result
in two identical daughter
cells.
Mitosis in a plant cell
Mitosis in an onion root