Question

Assertion: Prokaryotic cells have no membrane-bound organelles
Reason: The cytoplasm of prokaryotic cells does not show a streaming movement.
(a) Both assertion and reason are correct and the reason is the correct explanation for assertion
(b) Assertion is correct but the reason is incorrect.
(c ) Both assertion and reason are correct but the reason is not the correct explanation for the assertion.
(d) Both assertion and reason are incorrect.

Answer 1

Cells are divided broadly into two groups based on whether they possess membrane-bound organelles or not. Bacteria are included in prokaryotic cells. The cytoplasmic streaming movement ensures a homogenous distribution to all the parts of the cell.

Complete answer:
The prokaryotic cell lacks a membrane-bound nucleus as well as organelles. The circular genome lies naked in the cytoplasm with some proteins that aids in its coiling and supercoiling. This particular region in the cytoplasm is known as the nucleoid. The cytoplasm is the matrix that holds all of the organelles inside the cell together. It also stores nutrients and enzymes for metabolic processes. Cytoplasm streaming is one of the processes by which a cell helps in the equal distribution of nutrients to all its organelles. This is aided by the cytoskeleton. Since there are no cell organelles in a prokaryotic cell, thus no streaming movement can be observed in the cytoplasm of prokaryotic cells.

Additional Information:
-Cytoskeleton is made of actin and tubules. They provide a framework and help in the function of any cellular movements or locomotion. They are also responsible for continuous cytoplasmic streaming in a eukaryotic cell.
-The prokaryotes and eukaryotes also differ in the type of ribosomes. In prokaryotic cells, 70S ribosomes are present while in eukaryotic cells, 80S ribosomes are present.
-Ribosomes are small circular structures that are involved in the protein machinery. In prokaryotes, they lie independently in the cytoplasm while in eukaryotes, some are associated with rough endoplasmic reticulum while some lie independently in the cytoplasm.

So, the correct answer is ‘ Both assertion and reason are correct and the reason is the correct explanation for the assertion.’

Note:
-According to the five-kingdom biological classification given by R.H.Whittaker in 1969, all the prokaryotes are included in Kingdom Monera.
-These include Mycoplasma, Bacteria, Actinomycetes, and Cyanobacteria.
-The rest of the five kingdoms are Protista, Fungi, Plantae, and Animalia.