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A prokaryotic cell consists of the following structures:

Average prokaryote cell-es

No.

Name of structure

Description

Function

1.

Capsule or Slime layer

Outermost thick mucilaginous layer

  • Adhesion to the host  body.
  • Protection against phagocytes and  viruses.

2.

Cell wall

  • Present below glycocalyx.
  • Made up of peptidoglycan (murein) in Eubacteria; pseudomurein in  Archaebacteria.
  • Consists of polysaccharide chains  cross-linked with short amino acid  chains.
  • Provides rigidity and support.
  • Determines cell shape.

3.

Plasma membrane

  • Innermost layer of cell envelope.
  • Forms the boundary of cytoplasm.
  • Chemically, lipoproteinous in nature.
  • Phospholipid bilayer with intrinsic and extrinsic proteins.
  • Protects cell from injury.
  • Selective permeability.
  • Intercellular communication.
  • Site for respiration, photosynthesis, etc.
  • Serves as point of attachment.

4.

Mesosomes

Invaginations of the plasma membrane in the form of vesicles, tubules and lamella.

  • Cell wall formation.
  • Replication of DNA and distribution to daughter cells.
  • Increase the surface area of plasma membrane.
  • Contains respiratory enzymes.

5.

Cytoplasm

Colourless, semi-fluid, ground substance present inner to the cell membrane.

 

6.

Inclusion bodies

  • Non-living structures present in cytoplasm.
  • Include storage granules.
  • Organic inclusion bodies – Cynophycean starch, protein granules.
  • Inorganic inclusion bodies – Volutin (phosphate), sulphur, iron granules.

Storage of reserve food.

 

7.

Ribosomes

  • Small, sub-microscopic ribonucleoprotein particles.
  • Made up of RNA and proteins.
  • 70S type ( 50S and 30S)

Site of protein synthesis.

8.

Nucleoid

(Genophore)

  • Naked, double stranded DNA molecule.
  • Histone proteins, nucleolus and nuclear membrane absent.

Genetic material of the cell.

9.

Plasmids

Autonomously replication, double stranded circular DNA molecules present in cytoplasm.

  • Antibiotic resistance
  • Fertility.

10.

Flagella

One or more long, fine, thread-like structures present in bacteria.

Help in locomotion.

11.

Pili

Long, few, thick tubular structures made up of protein pilin.

Formation of conjugation tube for exchange of genetic material.

12.

Fimbriae

Small, narrow structures produced in large numbers (300-400 per cell)

Attachment of bacteria to solid surface or host tissue.

 

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