Tag: world of virus

• Bacterial capsule usually consists of a polysaccharide layer that lies outside the cell envelope. The capsule is found in both gram-positive and gram-negative bacterium.
• The capsule is considered as virulence factor because it enhances the ability of bacteria to cause disease. It protects the bacterial cell from engulfment by macrophages.
• Capsules also contain water which protects the bacterium from desiccation.

The ageing is very slow or is not seen with the human eye in unicellular organisms but they do age. They undergo constant spontaneous DNA damage that can lead to the death of cells when it no longer able to reproduce. Plants and parrot are multicellular organisms with the higher level of complexity. The complexity is such that cell divisions are limited and when the cell is not able to divide, it ages with the decay of organelles and finally dies. So these organisms do age and die after a perticular period of time. but Hydra is the only species that does not age and lose its capability to reproduce. So we can say that ageing is slow or absent in hydra.

Bacterial ribosomes are 70S, consisting of 30S and 50S subunits. The statement claiming they are 30 nm by 50 nm is incorrect as these numbers refer to the Svedberg units of the subunits, not the physical dimensions in nanometers.

• Mesosomes are absent in eukaryotes.
• Mesosomes refers to the folded invaginations in the plasma membrane of prokaryotes or bacterial cells.
  
• Its main function is to increase the surface area of the plasma membrane. 
• When the surface area of the membrane is increased it helps to carry out the cellular respiration more efficiently.
  
• So, the correct answer is 'Mesosome'.

Escherichia coli is a Gram-negative, facultatively anaerobic bacteria. It is found in the intestine of warm-blooded organisms. It has one circular chromosome. The chromosome contains double-stranded DNA. It may contain some circular plasmids as well as extrachromosomal material.

• Mitochondria are absent in bacteria and blue-green algae.
  
• A prokaryotic cell lacks membrane-bound cell organelles and nucleus whereas, a eukaryotic cell consists of membrane-bound cellular organelles and well-defined nucleus.
  
• Red algae, green algae and brown algae have eukaryotic cells (well-defined nucleus and cellular organelles).
• So, the correct answer is 'Bacteria'.

Acetabularia is a single-celled green photosynthetic algae which contain chloroplasts of the photosynthetic function. Being unicellular it has a complex shape and has been a model organism for the study of gene expression with morphogenesis. It has a large nucleus which contains a genetic material. Because of the presence of nucleus which is absent in prokaryote, these algae is classified in eukaryotes. hence algae Acetabularia is a unicellular eukaryote.

A. Amphitrichous bacteria have flagella (single or multiple) extending from both ends of the cell.

Amphitrichous bacteria possess a single flagellum or a tuft of flagella at both poles of the cell. This distinguishes them from peritrichous (all over) or lophotrichous (tuft at one end) arrangements.