Biological Classification — BIOLOGY STD 11 Science — Question

Cell envelope: It is the outer covering of protoplasm of bacterial cell. It contains mucilage sheath, cell wall and plasma membrane.

Cytoplasm: It is a crystallo colloidal complex that forms the protoplasm excluding its nucleoid. Membrane bound cell organelles are absent. Cytoplasm along with nucleoid are together called as protoplasm.

Nucleoid: It represents the genetic material of prokaryotes. Nucleoid consists of a single circular strand of DNA duplex which is super coiled with the help of RNA. No nuclear envelope is present.

Plasmids: These are self-replicating, extrachromosomal segments of double-stranded, circular, naked DNA.

Flagella: These are unstranded, equivalent to a single microtubular fibre. These help in movement and locomotion.

Pili and fimbriae: Pili are longer, fewer and thicker tubular outgrowths made up of protein pilin. Fimbriae are small bristle-like fibres sprouting from cell surface in large number. Pili are helpful in attaching to recipient cell and forming conjugation tube. Fimbriae cause agglutination of RBC. They also help in mutual clinging of bacteria.