Chapter 4, Problem 1MC

Which of the following is/are found only in prokaryotic cells?

a. plasmids

b. a cytoskeleton

c. mitochondria

d. ribosomes

Summary Introduction

Introduction:

Prokaryotes are mostly single-celled organisms with a distinct cell wall for protection and a cell membrane that is involved in cell transport. These cells are less complex than a eukaryotic cell. A major difference is that prokaryotes do not have a discrete nucleus.

Answer to Problem 1MC

Correct answer:

Plasmids are found in prokaryotes only.

Explanation of Solution

Justification for the correct answer:

Option (a) is given that only prokaryotes contain plasmids. The plasmid is an extrachromosomal circular deoxyribonucleic acid (DNA) segment that contains essential genes that provide resistance to the organism against stressful conditions. This DNA material can be transferred to another cell during reproduction. The prokaryotic cell is very small in size and accommodating a single large chromosome is difficult, therefore these plasmids contain a lot of essential genes in addition to the DNA molecule. Hence, option (a) is correct.

Justification for incorrect answers:

Option (b) is given that the cytoskeleton is a part of the prokaryotic cell only. The cytoskeleton is present in all eukaryotic as well as prokaryotic cells. It is essential for providing a cell with its shape and cell movement. So, it is an incorrect option.

Option (c) is given that only prokaryotic cells have mitochondria. This is not true as these primitive cells lack in membrane-bound organelles. Mitochondria is an organelle used for producing energy in the cell. Instead of utilizing mitochondria, a prokaryotic cell makes the use of its cell membrane for aerobic respiration. So, it is an incorrect option.

Option (d) is given that ribosomes are unique to prokaryotes. All living cells have ribosomes as they help in the production of proteins which are important for life. The only difference is in the type of ribosomes in eukaryotes and prokaryotes. So, it is an incorrect option.

Hence, options (b), (c), and (d) are incorrect.

Conclusion

Thus, it can be concluded that only prokaryotes contain plasmids. Cytoskeleton and ribosomes are found in both eukaryotes and prokaryotes, while mitochondria are only found in eukaryotes.