Question

Read the given statements and select the correct option. Statement \(1:\) In prokaryotes mitochondria are absent. statement \(2:\) In prokaryotes mesosomes are present which help in respiration. (a) Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1 . (b) Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1 . (c) Statement 1 is correct and statement 2 is incorrect. (d) Both statements 1 and 2 are incorrect.

Short answer

Both statements are correct, but statement 2 is not the correct explanation of statement 1. The answer is (b).

Step-by-step solution

Analyze Statement 1

Examine the first statement to determine its validity. Prokaryotes are organisms without a nucleus or other membrane-bound organelles. Since mitochondria are a type of membrane-bound organelle found in eukaryotic cells, it is correct that mitochondria are absent in prokaryotic cells.

Analyze Statement 2

Evaluate the second statement's accuracy. Mesosomes are infoldings in the plasma membrane of prokaryotic cells that are thought to help in the cellular processes such as respiration or cell division. While their exact function is sometimes contested, it is broadly accurate to state that mesosomes are present in prokaryotes and are associated with respiration.

Assess Relationship Between Statement 1 and 2

Determine if statement 2 provides a correct explanation of statement 1. Since the presence of mesosomes is indeed a feature of prokaryotic cells and they help in respiration, but this is not directly connected to the absence of mitochondria as the reason. The facts are correct, but statement 2 is not explaining the absence of mitochondria in prokaryotes.

Key concepts

Mitochondria in Eukaryotes

Mitochondria are often referred to as the powerhouse of eukaryotic cells. These tiny structures play a critical role in generating energy, making it possible for the cell to perform various functions.

Each mitochondrion is enclosed by two membranes – an outer membrane, which serves as a barrier between the mitochondrion and the cytoplasm, and an inner membrane, which holds the components necessary for energy production. Within the inner membrane is the matrix, containing enzymes for the citric acid cycle, as well as DNA and ribosomes.

One key attribute of mitochondria is their ability to produce ATP (adenosine triphosphate) through a process known as cellular respiration. This is how the cell captures and utilizes energy. The presence of their own DNA suggests mitochondria were once independent prokaryotic organisms that were engulfed by ancestral eukaryotes, an event known as endosymbiosis.

Importance of Mitochondria

These organelles are not just energy producers; they are deeply involved in regulating the cell cycle and cell death, signaling processes, and are even implicated in disease states when dysfunctions occur. The uniqueness of mitochondria lies in their dual genetic heritage and their critical symbiotic relationship within eukaryotic cells.

Mesosomes Function

Mesosomes are a somewhat controversial component found in many prokaryotic cells, mainly bacteria. These structures, formed by the invagination of the plasma membrane, were initially thought to be involved in various cellular functions, including respiration and DNA replication.

In the context of respiration, these folded structures were believed to increase the surface area of the cell membrane, providing more space for respiratory enzymes to function effectively – similar to the role of mitochondrial cristae in eukaryotes. The enhanced surface area could facilitate the electron transport chain, which is vital for ATP generation in prokaryotes.

However, the function of mesosomes is disputed among scientists. Some consider them artifacts created during cell fixation for electron microscopy, while others believe they play a role in cell division by aiding the distribution of genetic material. The debate continues, but many still recognize their potential importance in prokaryotic respiratory processes.

Prokaryotes vs Eukaryotes

Understanding the differences between prokaryotes and eukaryotes is fundamental in biology. Prokaryotes, which include bacteria and archaea, are unicellular organisms that lack membrane-bound organelles such as the nucleus and mitochondria. Their DNA is typically contained in a single circular chromosome.

Eukaryotic cells, on the other hand, have a distinct nucleus that houses their DNA, along with a variety of other membrane-bound organelles like mitochondria and the endoplasmic reticulum. Eukaryotic organisms can be either unicellular or multicellular, and this complex cell structure is believed to have evolved from prokaryotic ancestors through endosymbiosis.

Key Differences

• Cell Structure: Prokaryotic cells are generally smaller and simpler, while eukaryotic cells have more complex structures.
• Genetic Material: Prokaryotes have DNA in a nucleoid region, whereas eukaryotes have a membrane-bound nucleus.
• Membrane-Bound Organelles: Prokaryotes do not have them, while eukaryotes contain a variety of such organelles, including mitochondria, which aid in energy production.
• Reproduction: Most prokaryotes reproduce asexually through binary fission, while eukaryotes have more diverse and complex mechanisms of reproduction, including both sexual and asexual processes.

The understanding of these differences is not merely academic — it has practical implications in areas like medicine, where antibiotics may target structures unique to prokaryotes, and in biotechnology, where eukaryotic cells’ complex internal machinery is exploited for purposes such as drug and vaccine production.