Question

Alginic acid is produced by:
(A) Red alga
(B) Green alga
(C) Blue Green alga
(D) Brown alga

Answer 1

Algae is a large group consisting of photosynthetic eukaryotic organisms. They may be unicellular or multicellular. Algae have a range of reproductive strategies from simple asexual reproduction to sexual reproduction. Algae are different from plants in not having phyllids, roots, leaves, and other organs.

Complete answer:
Algae are photosynthetic organisms that lack a well-defined body and are mainly free-living. Algae are of different types which include:

Red algae, also called Rhodophyta belongs to the class Rhodophyceae. It is found in marine as well as freshwater. They have a characteristic red color due to the presence of phycocyanin and phycoerythrin pigments. They don't have chlorophyll b or beta carotene.
Green algae belong to class Chlorophyceae, which consists of a large group having photosynthetic pigments which includes chlorophyll a and chlorophyll b. They also contain xanthophylls and beta carotenes. They may be unicellular, multicellular, colonial, and flagellates. Examples include Spirogyra, Volvox
Brown algae belong to class Rhodophyceae, a large group consisting of multicellular algae. They are mostly marine. They contain fucoxanthin responsible for their distinctive color.
Alginic acid, also called Alginate, is a polysaccharide that is anionic and hydrophilic in nature. It is a linear polymeric molecule made up of D- mannuronic acid and L-glucuronic acid. They are present in the cell wall of brown algae. In brown algae, the cell wall has cellulose which is covered by a gelatinous coating of alginic acid.
Brown Green algae, also called cyanobacteria, is a false alga as they are unicellular. They are prokaryotic and photosynthetic and are classified with bacterias under Kingdom Monera.

So, the correct answer is option (D) Brown alga.

Note: Alginate has a good water-absorbing capacity which makes them useful in dehydrated products like slimming aids. They are used in the manufacturing of textiles and papers. Alginate is used as a hydrogel. Calcium alginate is used in medical products like wound dressings to promote healing.