Question

An organic substance that can withstand environmental extremes and cannot be degraded by any enzyme is-

• A. sporopollenin
• B. cuticle
• C. cellulose
• D. lignin

Answer 1

The correct option is A

sporopollenin

The correct option is A

Explanation of correct option

1. Sporopollenin is a highly cross-linked polymer made of hydrogen, oxygen, and carbon.
2. It is found in the outer wall of pollen grains and spores of all land plants.
3. It is resistant to the action of enzymes, strong acids, high temperatures, and strong alkali.
4. Thus it has been found to be extremely stable and chemically intact in sedimentary rocks which date back to 500 million years ago.

Explanation of incorrect option

Option B

1. The cuticle is the outermost protective covering found in leaves, flowers, non-woody stems, and fruits.
2. It protects the plant from extreme temperatures, chemical attacks, pest/ pathogen infestation, mechanical injuries, and other external stress.
3. Cuticles are susceptible to certain enzymes secreted by the fungus during infection or molting.

Option C

1. Cellulose is a complex polysaccharide found in the cell wall of algae, oomycetes, and green plants.
2. The linkages present in cellulose can be degraded by cellulases. Certain microbes like bacteria and fungi cause cellulose hydrolysis.
3. They are also decomposed when temperatures are near freezing or above 65°C.

Option D

1. Lignin is majorly found in the bark and wood region of plant cell walls. It provides mechanical support, resistance to stress, and water transportation.
2. Fungi and bacterial invasion is seen on wood surfaces where moisture content is high. Enzymes like lignin peroxidase, laccase, and manganese peroxidase breaks down lignin.

Final answer

An organic substance that can withstand environmental extremes and cannot be degraded by any enzyme is sporopollenin.