Ultrastructure of cells:
Cells are generally very small and are invisible without a microscope. Eukaryotic cells vary between
10 and 100 μm in diameter, while prokaryotic cells range from 0.1 to 5.0 μm in diameter.
Main differences between prokaryotic and eukaryotic cells are:
● Prokaryotes don’t have a nucleus
● In eukaryotic cells, the ribosomes are bigger, more complex and bound by a membrane (80S
vs 70S)
● Compared to eukaryotic cells, prokaryotic cells only have 1 chromosome (humans have 23)
Prokaryotes Eukaryotes
Type of Cell Always unicellular Unicellular and multi-cellular
Cell size Ranges in size from 0.2 μm – Size ranges from 10 μm –
2.0 μm in diameter 100 μm in diameter
Cell wall Usually present; chemically When present, chemically
complex in nature simple in nature
Nucleus Absent. Instead, they have a Present
nucleoid region in the cell
Ribosomes Present. Smaller in size and Present. Comparatively larger
spherical in shape in size and linear in shape
DNA arrangement Circular Linear
Mitochondria Absent Present
Cytoplasm Present, but cell organelles Present, cell organelles
absent present
Endoplasmic reticulum Absent Present
Plasmids Present Very rarely found in
eukaryotes
Ribosome Small ribosomes Large ribosomes
, Lysosome Lysosomes and centrosomes Lysosomes and centrosomes
are absent are present
Cell division Through binary fission Through mitosis
Flagella The flagella are smaller in size The flagella are larger in size
Reproduction Asexual Both asexual and sexual
Example Bacteria and Archaea Plant and Animal cell
Figure 1. Generalised prokaryotic cell.
● Spaghetti: 1 big chromosome
● Bacteria cells don’t have nucleus
● Bacterial flagellum do not have microtubules
● Pili function is to attach to other surface
Cells are generally very small and are invisible without a microscope. Eukaryotic cells vary between
10 and 100 μm in diameter, while prokaryotic cells range from 0.1 to 5.0 μm in diameter.
Main differences between prokaryotic and eukaryotic cells are:
● Prokaryotes don’t have a nucleus
● In eukaryotic cells, the ribosomes are bigger, more complex and bound by a membrane (80S
vs 70S)
● Compared to eukaryotic cells, prokaryotic cells only have 1 chromosome (humans have 23)
Prokaryotes Eukaryotes
Type of Cell Always unicellular Unicellular and multi-cellular
Cell size Ranges in size from 0.2 μm – Size ranges from 10 μm –
2.0 μm in diameter 100 μm in diameter
Cell wall Usually present; chemically When present, chemically
complex in nature simple in nature
Nucleus Absent. Instead, they have a Present
nucleoid region in the cell
Ribosomes Present. Smaller in size and Present. Comparatively larger
spherical in shape in size and linear in shape
DNA arrangement Circular Linear
Mitochondria Absent Present
Cytoplasm Present, but cell organelles Present, cell organelles
absent present
Endoplasmic reticulum Absent Present
Plasmids Present Very rarely found in
eukaryotes
Ribosome Small ribosomes Large ribosomes
, Lysosome Lysosomes and centrosomes Lysosomes and centrosomes
are absent are present
Cell division Through binary fission Through mitosis
Flagella The flagella are smaller in size The flagella are larger in size
Reproduction Asexual Both asexual and sexual
Example Bacteria and Archaea Plant and Animal cell
Figure 1. Generalised prokaryotic cell.
● Spaghetti: 1 big chromosome
● Bacteria cells don’t have nucleus
● Bacterial flagellum do not have microtubules
● Pili function is to attach to other surface
