Question

Which of the following structures is not found in a prokaryotic cell?
A. Plasma membrane
B. Nuclear envelope
C. Ribosomes
D. Mesosome

Answer 1

Hint: The world has started from the primitives having a single cell with the simplest organization. Due to the changes in the environment, the body complexity increased and the organization became tough. These organisms were then placed in the eukaryotes category.

Complete answer: Bacterias are the most primitive organisms known to us. They are the prokaryotic cells. They do not have organelles bounded with membranes as they do not have a complex body. They even lack a membrane around the nucleus. The bacterial cell wall is composed of peptidoglycan (murein) made of polysaccharide chains. The thickness of this layer differentiated the bacterias into two labels -gram-positive and gram-negative. The nucleus is the brain of the cell which has the genetic material condensed in the nucleus of the cell. It is membraned in the eukaryotes and non-membrane in prokaryotes.
Option A: Plasma membrane: It is the outer membrane of the bacteria which allows only selective material to pass through them.
Option B: Nuclear envelope: The nucleus in prokaryotes is not well defined thus it lacks the nuclear envelope.
Option C: Ribosome: They are present both in prokaryotes and eukaryotes as they make the proteins that are mandatory for cell functioning.
Option D: Mesosome: Mesosomes increase the bacterial surface for respiration. They play a vital role in the cellular processes and cell wall division.
So the answer is option B: Nuclear envelope

Note: A large vacuole is found in eukaryotes. It is prominent and in the center of the cell. Bacterial cells lack vacuole. Bacterias occur in all shapes and sizes. They are mostly unicellular. Their one cell can perform all the cell functions. They can be motile or non-motile.