Question

Describe the ultrastructure of a prokaryotic cell?

Answer 1

Hint: Cell is a basic structural and functional unit of all living organisms. Based on the presence of a nucleus, cells are classified as eukaryotic or prokaryotic. Plant cell and animal cell are eukaryotic and bacterial cells are prokaryotic. The nucleus is present in animal and plant cell whereas, absent in the bacterial cell.

Complete answer: ’Pro’ stands for before and ‘karyon’ stands for kernel or nucleus. Prokaryotes can be easily differentiated from eukaryotic cells based on their cellular structure and molecular makeup. Prokaryotic cells have simple internal structures as compared to eukaryotic cell structures.
Many structures are the same in eukaryotic and in a prokaryotic cell. A prokaryotic cell has some unique structures. Features of prokaryotic organisms:
a) True membrane-bound nucleus is absent.
b) Cytoplasm shows the presence of ribosome and reserve deposits called inclusion bodies.
c) The histone protein is absent.
d) Number of chromosomes is one (mostly).
e) Mitosis and meiosis type of cell division is absent.
f) Genetic recombination is partial (unidirectional transfer of DNA).
g) Sterol in the plasma membrane is absent present only in Mycoplasma.
h) Ribosome present is the 70S.
i) Unit membrane-bound organelles are absent.
j) Cell wall is present in most prokaryotic cells.
k) Prokaryotic cells show similarities with eukaryotic organelles like mitochondria and chloroplast.
l) Presence of flagella organ of locomotion.
m) Thin hair-like appendages present known as pili.

Note: The endosymbiotic theory proposes that the mitochondria and chloroplasts of eukaryotic cells originated as symbiotic prokaryotic cells. The presence of the circular covalently closed DNA and 70S ribosomes in mitochondria and chloroplast support this theory.