Note on Structure of Prokaryotic Cell

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source:classes.midlandstech.edu

Structure of Prokaryotic Cell

A prokaryotic cell shows the following structures.

Simple layer/ Capsule

The cell is externally covered by a mucilaginous layer called slime layer. If it is thick, it is called capsule. It protects the cell from drying or desiccation.

Cell wall

It is a thick rigid protective layer which is chemically composed of murein. It gives distinct shape and protection to the cell.

Cell membrane

It is thin, elastic, semi-permeable membrane which is lipo-proteinous in chemical composition. It helps in respiration as it contains respiratory enzymes and also regulates the flow of materials in and out of the cell.

Cytoplasm

It is a granular, semi-fluid ground substance present throughout the cell. It contains inorganic and organic chemical compounds, enzymes, cell organelles like ribosomes and reserve food materials.

Nucleoid

It is the primitive type of nucleus which consist of genetic material in the form of highly folded, naked, circular DNA strand without histone protein.

Flagellum

It is a long thread-like structure made up of protein. It gives motility to the cell. The flagella do not show 9+2 arrangement.

Pili

Pili are short hair-like outgrowth made up of protein. They help in the arrangement. During reproduction, it helps in the formation of consultation tube.

Mysosome

These are finger-like infoldings of the cell membrane. They increase the surface area for respiration and also help during cell division.

Thylakoid

Thylakoids are a membrane-bounded sac-like structure which contains photosynthetic pigment and helps in photosynthesis.

Plasmid

Plasmids are the additional ring of DNA found in the cytoplasm. They contain genes or factors for fertility and resistance of the cell.

Plant cell Animal cell
The cell wall is present. Cell wall is not present.
Plastids are present. Plastids are absent.
Vacuoles are single and largely located. Vacuoles are small and large in numbers and is scattered in the cytoplasm.
Centriole is absent. Centriole is present.
The nucleus is located in the periphery. Nucleus is located in the centre.
They are polygonal in shape. They are circular in shape.
Lysosomes are absent. Lysomes are present.
The nucleus is elliptical in shape. Nucleus is round in shape.
A plant cell is generally large. Animal cell is small in size.
Reserved food materials are a starch. Reserved food materials are glycogen.
Mitochondria is fewer. Mitochondria is numerous.
Cristae of mitochondria in plant cell are tubular in shape. Cristae of mitochondria in the animal cell are the plate in shape.
Spindle apparatus is the ancestral type (without aster).

Spindle apparatus is an amphiastral type (having aster at the poles).

Smaller and numerous Golgi bodies i.e. dictyosomes. Single and large Golgi body or Golgi complex.
Cytokinesis occurs by cell plate method. Cytokinesis occurs by the cell celvage or furrowing method.
Plant cell does not undergo osmotic bursting. Animal cell easily undergoes osmotic bursting.

  • The cell is externally covered by a mucilaginous layer called slime layer. 
  • Cristae of mitochondria in plant cell are tubular in shape.
  • Pili are short hair like outgrowth made up of protein. 
  • Thylakoids are a membrane-bounded sac-like structure which contains photosynthetic pigment and help in photosynthesis.
  • Plasmids are additional ring of DNA found in the cytoplasm. They contain genes or factors for fertility and resistance of the cell.
  • Mysosomes  are finger like infoldings of the cell membrane. They increase the surface area for respiration and also help during cell division.
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