Basic Structure of a Cell
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I. Modern Cell Theory
A. Main Characteristics of Organisms
1. Made of CELLS
2. Require ENERGY (food)
3. REPRODUCE (species)
4. Maintain HOMEOSTASIS
5. ORGANIZED
6. RESPOND to environment
7. GROW and DEVELOP
8. EXCHANGE materials with surroundings
(water, wastes, gases)
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B.CELL THEORY
1.All living things are
made of cells
2.Cells are the basic unit
of structure and
function in an organism
(basic unit of life)
3. Cells come from the
reproduction of existing
cells (cell division)
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C. Robert Hooke
1. First to view cells
2. Robert Hooke (1665):
microscope to
examine a slice of cork
(dead plant cell walls)
3. Saw small boxes, and
called them “CELLS”
because they looked like
the small rooms that
monks lived in called
Cells.
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D. Other Scientists Contributed to the Cell
1.Matthias Schleiden: (1838)
plants made of cells;
cofounder of cell theory
2.Theodore Schwann: (1839)
animals made of cells;
cofounded the cell theory
3.Rudolph Virchow: (1855)
observed cells dividing using
a microscope; all cells come
from other pre-existing cells
by cell division
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E. Discoveries Since the Cell Theory
1.Endosymbiotic theory: One
organism begins to live within
another organism and both organism
benefit. Eventually, the two
organisms evolve to become one
new single organism.
2.Lynn Margulis (1970): evidence
that some organelles within cells
were at one time free living cells
themselves.
3.Examples: Chloroplast and
Mitochondria (have their own DNA)
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II. Modern Cell Theory
A. Cell Size and Types
1. Cells can only be observed under microscope
2. Cell range: 5 – 50 micrometers (microns;
1 cm = 10,000 microns) in diameter
3. Three basic types of cells include (Biggest
to smallest: plant, animal, bacteria):
i.Plant Cell
ii.Animal Cell
iii.Bacterial Cell 8
B. Number of Cells
1. Although ALL living things are made
of cells, organisms may be:
a. Unicellular – composed of one cell
b. Multicellular - composed of many
cells that may organize into tissues, etc.
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C. Prokaryotic or Eukaryotic
1.Prokaryotes include bacteria &
lack a nucleus or membrane-bound
structures called organelles
2. Eukaryotes include most other
cells & have a nucleus and
membrane bound organelles (plants,
fungi, & animals)
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D. Prokaryotes
1. The first cells
2. Cells that lack a nucleus or
membrane-bound organelles
3. Includes bacteria
4. Simplest type of cell
5. Single, circular chromosome
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D. Prokaryotes
6. Nucleoid region
(center) contains
the DNA
7. Surrounded by
cell membrane &
cell wall
(peptidoglycan)
8. Contain ribosomes
(no membrane) in
their cytoplasm to
make proteins
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E. Eukaryotic Cell
1. Contain 3 basic cell structures:
a. Nucleus
b. Cell Membrane
c. Cytoplasm with organelles
2. Two main types of eukaryotic
cells
a. Plant cells
b. Animal cells
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E. Eukaryotic Cell
3. Organelles
a.
b.
c.
d.
e.
Very small (Microscopic)
Perform various functions for a cell
Found in the cytoplasm
May or may not be membrane-bound
Examples:
i. Golgi Bodies – wrap & export proteins
ii. Nucleolus – makes ribosomes
iii. Lysosomes – digests & gets rid of wastes
iv. Ribosomes – makes proteins
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