Kingdom Monera - Cytoplasm

Description:

Cytoplasm is a crystallo-colloidal complex that forms the protoplasm excluding the nucleoid. Bacterial cytoplasm does not have membrane bound organelles although biochemical pathways are found in prokaryotes which are similar to those of eukaryotes. Bacterial cytoplasm shows presence of gas vacuoles.

Various structures present in cytoplasm are −

Mesosome

Mesosomes are ingrowth of plasma membrane. They consist of vesicles, tubules and lamellae.

The different types of Mesosomes are −

Septal mesosome −

• Connects nucleoid with plasma membrane.
• It takes part in replication of nucleoid by providing points of attachment to the replicated ones.
• Helps in septum formation.

Lateral mesosome −

• Not connected with nucleoid.
• Contains respiratory enzymes and often called chondrioid.
• It is believed to be equivalent to mitochondrion of eukaryotes.

Ribosome

• Small membraneless, ribonucleoproteins.

• Found in two forms: Fixed (attached to the plasma membrane) and free (occur free in cytoplasmic matrix).

• Ribosomes are 70S in nature consisting of two subunits, a larger 50S and a smaller 30S subunit.

• They take part in protein synthesis.

• Ribosomes generally occur in helical groups called polyribosomes or polysomes.

Chromatophores

• Occur in photoautotrophic bacteria.
• In purple bacteria they are covered by a normal membrane.
• In green bacteria they are covered by non-lipid protein membrane.
• Photosynthetic pigments are bacteriochlorophyll, bacteriophaeophytin and carotinoids.