Question

Gram positive bacteria differ from gram negative bacteria in the structure of their

• A. Nucleoid
• B. Cytoplasm
• C. Cell wall
• D. Ribosomes

Answer 1

Answer: (C)

Cell wall

The gram-negative cell wall is characterized by presence of outer membrane, a thinner peptidoglycan layer and extensive periplasmic space surrounding the peptidoglycan.

The uppermost layer of the outer membrane has lipopolysaccharide while the innermost layer is a typical lipid layer. Presence of membrane channels formed by porin proteins in outer membrane impart make them less penetrable as compared to gram positive cells.

Gram positive cells are characterized by presence of single thick layer of cell wall which is made up of peptidogycan, teichoic acid and lipoteichoic acid. They lack outer membrane and porin and have narrow periplasmic space. This makes option C correct.

Ribosomes are the site for protein synthesis and have two subunit; large and small. Prokaryotic ribosomes have 30S and 50S subunits that together make a 70S ribosome.

Both Gram positive and negative bacteria have unit cell membrane of phospholipids and 70S ribosomes. Both Gram positive and negative bacteria are characterized by absence of membrane bound true nucleus and presence of their heredity substance in the centre of cell as nucleoid. Thus the correct answer is option C.