Question

Read the given statements and select the correct option. Statement \(1:\) Chloroplast and mitochondria are semiautonomous bodies. Statement 2 : Chloroplast and mitochondria have their own DNA and protein synthesizing machinery. (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

(a) Both statements 1 and 2 are correct, and statement 2 is the correct explanation of statement 1.

Step-by-step solution

Analyze Statement 1

Examine the claim that chloroplast and mitochondria are semiautonomous bodies. 'Semiautonomous' means they can function to some extent independently within cells. This is true because chloroplasts and mitochondria can grow, replicate, and have some of their own machinery for essential processes.

Analyze Statement 2

Assess the accuracy of the claim that chloroplast and mitochondria have their own DNA and protein synthesizing machinery. This statement is also correct, as both chloroplasts and mitochondria contain their own DNA and are capable of synthesizing some proteins independently of the cell’s nucleic DNA.

Evaluate the Relationship Between the Two Statements

Determine if statement 2 is the correct explanation of statement 1. Since statement 2 provides reasons (their own DNA and protein machinery) for why chloroplasts and mitochondria can function semi-independently, it can be considered the correct explanation for statement 1.

Select the Correct Option

Given that both statements are correct and statement 2 is the correct explanation for statement 1, the correct option is (a).

Key concepts

Chloroplast Semiautonomous Bodies

Chloroplasts are considered semiautonomous bodies within plant cells. These organelles are known primarily for their role in photosynthesis, converting light energy into chemical energy stored in glucose. But beyond their function in harnessing sunlight, chloroplasts are fascinating because they retain their own genetic material and ribosomes, which grants them a certain degree of independence from the cell nucleus.

Like a city within a city, chloroplasts can grow and divide on their own, similar to bacteria. This mirroring of bacterial growth is a clue to their evolutionary past, as they originated from free-living prokaryotes that were engulfed by ancestral eukaryotic cells, leading to a symbiotic relationship.

DNA and Ribosomes

The presence of circular DNA within chloroplasts equips them with the instructions to manufacture some of the proteins necessary for their function. The ribosomes, although slightly different from those found in the cytoplasm of the cell, are where these proteins are synthesized within the chloroplast. This unique arrangement of having their own DNA and protein synthesis machinery is what stands at the core of their semiautonomy.

Self-Replication

Chloroplasts have the ability to replicate independently of the division of the cell they reside in. This is crucial for the maintenance of a high number of chloroplasts in cells that perform a lot of photosynthesis. The number and size of chloroplasts can vary, contributing to the cell's ability to adapt to various environmental conditions.

Mitochondria DNA and Protein Synthesis

Mitochondria are often hailed as the 'powerhouses of the cell' because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy. Aside from energy production, mitochondria hold significance as semiautonomous organelles with their own genome and protein production capabilities.

Contained within mitochondria is a set of genes on a small circular DNA molecule. This mitochondrial DNA (mtDNA) encodes for some of the proteins and enzymes required for mitochondrial function, particularly those involved in oxidative phosphorylation, the process by which ATP is produced.

Mitochondrial Ribosomes

Mitochondria contain ribosomes that are more similar to those found in bacteria, supporting the endosymbiotic theory which suggests that mitochondria are descended from a symbiotic relationship with bacteria. These ribosomal structures are responsible for translating the encoded information from mtDNA to produce vital mitochondrial proteins.As with the chloroplasts, the localized DNA and protein synthesis are not only indicative of their autonomy but also essential for their specific functions within the cell. This autonomous nature of mitochondria means that they too, like chloroplasts, can reproduce within the cell independently, ensuring that energy demands of the cell are met efficiently.

Cell Organelles Autonomy

The autonomy of cell organelles, specifically chloroplasts and mitochondria, is an attribute that allows these organelles to operate somewhat independently within the eukaryotic cell. This aspect of autonomy is integral to the cell's overall functioning and has implications for the evolution, inheritance, and cellular adaptations.

Autonomy within organelles is feasible due to their possession of separate genetic materials and the machinery to use these materials for their own protein synthesis. This separate genetic inheritance enables these organelles to have a degree of control over their own replication and function, which is particularly evident in abnormal or stressful conditions where their activities might need to be modulated independently of the nucleus.

Implications for Inheritance

Since mitochondria are inherited maternally, their autonomy also means that mitochondrial diseases are often handed down from mother to offspring. In contrast, chloroplasts are typically inherited through the maternal parent in plants, which can affect the phenotypic expressions in the flora.Understanding the autonomy of these organelles not only answers fundamental biological questions but also provides insights into potential therapies and bioengineering applications. Harnessing organelle autonomy could lead to innovations in medical treatments for mitochondrial diseases, as well as enhancements in crop yields and plant resilience to environmental stresses.