Question

Both plant and animal cells contain some small organelles called 'peroxisomes', which are dedicated to the metabolism of substances such as

• A. Fibre
• B. Sugar
• C. Fats and amino acids
• D. Starch

Hint:

Remember that glyoxysomes are specialized peroxisomes found in oil-storing plant seeds.
They contain enzymes of the glyoxylate cycle, allowing the direct conversion of stored fats into carbohydrates.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Peroxisomes are small, single-membrane-bound eukaryotic organelles containing various oxidative enzymes.
They play crucial roles in cellular lipid metabolism, chemical detoxification, and nitrogen metabolism.

Step 3: Detailed Explanation:
The primary physiological function of peroxisomes is to break down long-chain fatty acids (fats) and amino acids.
In animal cells, peroxisomes carry out the \(\beta\)-oxidation of very-long-chain fatty acids (VLCFAs) to shorten them.
These shortened fatty acids are then transported to the mitochondria for complete oxidation to generate energy.
In plant cells, \(\beta\)-oxidation is restricted exclusively to peroxisomes and specialized glyoxysomes.
During seed germination, glyoxysomes convert stored lipids into sugars to nourish the growing seedling.
Peroxisomes also contain D-amino acid oxidases that break down toxic D-amino acids during metabolic processes.
A major byproduct of these oxidation reactions is hydrogen peroxide (\(\text{H}_2\text{O}_2\)), which is highly cytotoxic.
To neutralize this threat, peroxisomes are rich in the enzyme catalase, which degrades \(\text{H}_2\text{O}_2\):
\[ 2\text{H}_2\text{O}_2 \xrightarrow{\text{Catalase}} 2\text{H}_2\text{O} + \text{O}_2 \] Let us analyze the other options:
Fibre consists of structural carbohydrates (like cellulose) located in the plant cell wall, not inside organelles.
Sugars are metabolized primarily in the cytosol through glycolysis and in the mitochondrial matrix.
Starch is synthesized and stored inside specialized plastids called amyloplasts in plant cells.
Therefore, peroxisomes are specifically dedicated to the metabolism of fats and amino acids.

Step 4: Final Answer:
The substances metabolized inside peroxisomes are fats and amino acids, matching Option (C).