 The
cell ; It is the smallest structural and
functional unit in living organisms.
 There are two types of cells ;
1-Prokaryotic cells , such as in Bacteria &
Archaea.
2- Eukaryotic cells ,such as in animal and
plant cells.
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The first living organisms to
evolve.
Are primarily distinguished by
the fact that they lack a
membrane-bound nucleus, thus
the genetic material is found
naked in the cytoplasm.
They are small in size 1-10µm.
They are single celled.
They have simple internal
structures.
They contain no cell organelles
(only the ribosomes which are
not considered as cell
organelles.)
Reproduce by means of binary
fission, duplicating their genetic
material and then essentially
splitting to form two daughter
cells identical to the parent
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Most important feature is that they
contain a well defined nucleus
meaning that the genetic material
is separated from the rest of the of
the cell by a nuclear membrane.
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Are larger in size 10-100µm.
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Are found in single and
multicellular organisms.
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It has a complex internal structure
(contains a large number of cell
organelles)
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Reproduces by Meisos or Mitosis.
 Nucleus;It
is surrounded by a double layered
nuclear membrane which contains pores to
allow exchange of material between nucleus
and rest of the cell.
 Contains the genetic material.
 Nucleolus
Is the site
For
rRNA
Synthesis.
 Endoplasmic
reticulum; - Tubular network
fused to nuclear membrane
- Goes through cytoplasm onto cell
membrane
- Stores, separates, and serves as cell's
transport system
- Smooth type: lacks ribosomes
- Rough type ;ribosomes embedded in
surface can
Synthesize protein.
 Golgi
apparatus;
- Important in packaging and secretion of cell
products.
- A membrane structure found near nucleus
- Composed of numerous layers forming a
sac.
 Mitochondria;
Second largest organelle with unique genetic
structure.
- Double-layered outer membrane with inner
folds called cristae
- Energy-producing chemical reactions and
ATP production site.
Lysosome
Contains digestive enzymes to digest proteins,
lipids, and carbohydrates
- Transports undigested material to cell
membrane for removal.
 Chloroplasts
A plastid usually found in plant cells
- Contain green chlorophyll where photosynthesis
takes place.
 Vacuoles
Membrane-bound sacs for storage, digestion, and
waste removal in plant cells.
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Ribosomes; Site of protein biosynthesis.
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Stationary ribosomes are bound to the RER.
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Free ribosomes in cytoplasm.
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Not surrounded by plasma membrane and is made up of rRNA and
protein.
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Plasma membrane
Outer membrane of cell that controls cellular traffic.
- Made up of a phosphiolipid bilayer and proteins that span
through the membrane and allow passage of materials.
Example E.Coli
Component
Percent total weigh
Approxmate No of
Molecular species
Water
70
1
Proteins
15
3000
DNA
1
1
RNA
6
1000
Carbohydrates
3
50
Lipids
2
40
Building-block
molecules&intermediat
es
2
500
Inorganic ions
1
12
Nucleic acids
 Viruses
structure : protein coat + genetic
material ( DNA or RNA )
 Viruses do not have a cellular structure.