Cell Structure and Organelles

Prokaryotic plasma membrane contains phospholipids as the major component.

Lysosomes are the single membrane-bound organelles found only in animal cells. They have acidic pH and acid hydrolases enzymes that perform degradative function.

Chromatophores are absent in the plant cells as these are the specialised photosynthetic structures present in the cyanobacteria and photosynthetic bacteria only.

Peroxisomes are single membrane bound cell organelles that contain oxidases and catalases enzymes. The enzyme catalases protects other cell organelles from the toxic effects of H₂O₂ by converting it into water and oxygen.

Group translocation does not occur in eukaryotic cells. They perform endocytosis as an alternative mechanism whereas endocytosis is absent in prokaryotes. Therefore, group translocation is present only in prokaryotes.

Vacuoles are the important cell organelles present in the plant cells. They usually consume about 30 percent of the cell’s volume. Vacuoles are important as they help in adjusting size and turgor pressure of the plant cells. Vacuoles are the cell organelles that share similarity with the lysosomes of animal cells as both contain degradative enzymes for breaking down macromolecules. In plants, vacuoles also serve as storage compartments for metabolites and nutrients.

All lysosymal enzymes work best at acidic pH and therefore they are known as acid hydrolases. They do not work efficiently at basic pH. The inside of the lysosome is maintained at 4.8 pH with the help of special hydrogen ion pump.

Streptomycin and erythromycin are types of antibiotics that specifically act on the 70s ribosomes of prokaryotes and thus do not act on the 80S ribosomes of eukaryotic cells. However, mitochondrion contains 70 S ribosomes, it is most likely to get affected if it is treated with streptomycin or erythromycin antibiotic.

As gram positive bacterium lacks the outer lipopolysaccharide layer, the basal body of the flagellum in it has only the inner pair of rings and the outer pair of rings are absent in gram positive bacteria. Hence, this statement is not correct.

Chromatin starts to condense and the chromosomes become visible microscopically, once this phase completes.

Bacterial flagellum consists of three basic parts: the filament, hook and the basal body. The third part – basal body, is very important as it consists of several rings that anchor the flagellum into the plasma membrane and the cell membrane. A gram negative bacterium contains two pairs of rings that are attached to the different layers of the cell wall and the outer pair is specifically attached to the outer layer of the cell wall. As the outer cell wall is absent in a typical gram positive bacterial cell wall, it contains only the inner pair of rings that are inserted into the cell wall and plasma membrane. This structural arrangement of flagellum differentiates gram positive and gram negative bacterial cell’s flagella.

Muramic acid is present in the bacterial cell wall and therefore it is not the constituent of plasma membrane.

Membrane proteins are produced on the rough endoplasmic reticulum and are carried forward with the help of membrane-bounded transport vesicles. Subsequently, these proteins are carried to the luminal cavity of the golgi complex, where they are processed.

Blood cells, particularly red blood cells, lack mitochondria.

Golgi complex consists of a series of flattened membrane vesicles or sacs surrounded by spherical membrane vesicles. The three well-defined regions that are present in the stack of the flattened golgi sac include cis, medial and trans. Secretory proteins and membrane proteins from the rough endoplasmic reticulum first reach the cis region of the golgi complex, and then move to the medial region and ultimately to the trans region. While passing through all these regions, they undergo modifications by the specialised enzymes of the sacs.