Class 11 Biology - Chapter Cell: The Unit of Life NCERT Solutions | What are the characteristics of prokaryo
What are the characteristics of prokaryotic cells?
The characteristics of prokaryotic cells are as follows:
(i)They are generally small in size. The size of a prokaryotic cell varies from 0.5 – 5 µm.
(ii) The nuclear region of a prokaryotic cell is poorly-defined because of the absence of a nuclear membrane. Hence, a prokaryotic cell lacks a true nucleus.
(iii) The genetic materials of prokaryotic cells are naked. They contain single, circular chromosomes. In addition to the genomic DNA, they have a small, circular plasmid DNA.
(iv) They have specialised membranous structures called mesosomes. Mesosomes are formed by the invagination of the cell membrane. These extensions help in the synthesis of the cell wall and replication of DNA. They also help in the equal distribution of chromosomes into the daughter cells.
(v) Membrane-bound cell organelles such as mitochondria, plastids, and endoplasmic reticulum are absent from a prokaryotic cell.
(vi) Most prokaryotic cells contain a three-layered structure – outermost glycocalyx, middle cell wall, and the innermost plasma membrane. This structure acts as a protective unit.
Examples of prokaryotic cells include blue green algae, bacteria, etc.
More Questions From Class 11 Biology - Chapter Cell: The Unit of Life
- Q:-
Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
- Q:-
Multicellular organisms have division of labour. Explain.
- Q:-
What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
- Q:-
Cell is the basic unit of life. Discuss in brief.
- Q:-
What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
- Q:-
Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials. - Q:-
Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
- Q:-
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome - Q:-
What are nuclear pores? State their function.
- Q:-
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
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