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What is true about genetic material of a prokaryotic cell?
In prokaryotes, the genetic material consists of single circular DNA molecule lying entangled in nucleoid. It is not bounded by a definite nuclear membrance. Histones are water-soluble proteins rich in arginine and lysine that help in DNA packaging in chromosomes. Prokaryotic cells lack pistone proteins.
Arrange the following steps in a correct sequeence as per Gram's staining technique:
Treatment with 0.5% iodine solution (1). washing was water (2). treatment with absolute alcohol/acetore (3). staining with weak alkaline solution of crystal violet (4).
The grouping of bacteria is based upon reaction of bacteria to Grams's stain (Christian Gram, 1884). Bacteria are first stained with weakly alkaline solution of crystal violet and then treated with 0.5% iodine solution. This is followed by washing with water and then with alcohol or acetone. Bacteria which retain blue of purple colour are known as (Gram(+) bacteria (e.g., Bacillus subtilis). Bacteria which do not retain any stain and become colourless are called Gram(-) bacteria (e.g., Escherichia colt). Washing of the stain in Gram(-ve) bacteria is due to high lipid content of their cell wall which gets dissolved in organic solvents like acetone.
Prokaryotic cells are generally _____ and multiply _____ than the eukaryotic cells.
Prokaryotic cell is usually small (0.1-5.1μm) in size whereas eukaryotic cell size is comparatively larger (5-100μm). Prokaryotic cells multiply very rapidly by asecial means like binary fission, sporulation etc.
Mesosomes are the infoldings of cell membrane, which
(i) are present in both prokaryotic and eukaryotic cells.
(ii) help in cell wall formation, DNA replication and respitation.
(iii) increase the surface area of plasma membrane.
Mesosomes are present only in prokaryotes.
Glycocalyx (mucilage sheath) of a bacterial cell may occur in the form of a loose sheath called ____ or it may be thick and tough called _____ .
Glycocalyx (mucilage sheath) is the outermost layer of the bacterial cell envelope which consists of non-cellulosic polysacharides with or without proteins. It may occur in the form of loose sheath, called slime layer. If it is a thick coering, it is called capsule. Glycocalyx gives sticky character to the cell and is not absolutely essential for survival of bacteria. It prevents desiccation, protects from phagocytes, toxic chemicals and viruses and serves in attachment. It may give selective advantage though in certain situations.
Correct sequence of layers of bacterial cell envelope from outward to inward is
Glycocalyx is the outermost layer of the cell envelope. Cell wall lies between plasma membrane andd glycocalyx.
_____ are self replicating, extra chromosomal segments of double stranded circular and naked DNA, present in a bacterial cell.
Plasmid is a structure in bacterial cell consisting of DNA that can exist and replicate independently of the chromosome. Plasmids provide genetic instructions for certain cell activities (e.g., antibiotic, resistance). They can be transferred from cell to cell in a bacterial colony.
Read the given statements and select the correct option.
Statement 1: In prokaryotes mitochondira are absent.
Statement 2: In prokaryotes mesosomes are present which help in respiration.
Mitochondria are absent in prokaryotes. Mesosomes are characteristic circular to villiform specialisation of cell membrance of bacteria that develop as an ingrowth from the plasma membrane. It helps in nucleoid replication and cell division. Lateral mesosome is not connected with nucleoid. It contains resspiratory enzymes and is, therefore, often called chondrioid. It is believed to be equal to mitochondrion of eukaryotes. However, respiratory enzymes are also present over the plasma membrane.
The type of ribosomes found in prokaryotes is
The cytoplasmic ribosomes of prokaryotes (blue green algae, bacteria and PPLOs) are 70S. They have two subunits 50S and 30S.
If you remove the fimbriae from the bacterial cell, which of the following would you expect to happen?
Fimbriae are hair like structures present in large number in bacteria. They help in attaching bacteria to solid surface or host tissues.