Problem 23 - Objective Biology for NEET

Question

Algin is secreted by (a) All of the algae (b) Only brown algae (c) Only red algae (d) Both red and brown algae

Step-by-Step Solution

Answer

The correct answer is (b), Algin is secreted by only brown algae.

Step 1 Identify Algae Types

Firstly, it is crucial to understand the different types of algae mentioned in the options: brown algae, red algae and all algae.

Step 2 Clarify Algin

Secondly, the concept of Algin needs to be defined. Algin or Alginic acid is an anionic polysaccharide distributed widely in the cell walls of brown algae.

Step 3 Match Algae with Algin

With knowledge about Algin and its relation to algae, it can be concluded that Algin is secreted by only brown algae.

Key Concepts

Brown Algae

When exploring marine ecosystems, you'll frequently encounter brown algae, which distinguishes itself with a unique color that ranges from olive green to dark brown. This coloration is due to the presence of fucoxanthin, a pigment that overshadows the green of chlorophyll. Brown algae are primarily found in cold, temperate waters and have an intricate structure, often growing to a substantial size.

Key to understanding their role in marine life is their unique composition. The cell walls of brown algae contain a substance known as algin or alginic acid. This compound is not just important for the structural integrity of the algae, but it has found numerous applications in our daily lives. For instance, it is widely used as a stabilizer and thickening agent in ice creams, jellies, and even in non-food items like pharmaceuticals and textiles due to its ability to absorb water. Remarkably, algin from brown algae can also be utilized in wound dressings, as it has properties that can absorb excess fluids and promote healing.

Anionic Polysaccharide

An anionic polysaccharide is a negatively charged complex carbohydrate that is composed of long chains of sugar molecules. This designation as 'anionic' comes from its ability to attract positively charged ions or cations in aqueous solutions. Alginic acid is a stellar example of an anionic polysaccharide found in the cell walls of brown algae. Its molecular structure allows it to form a gel-like substance when it comes into contact with water.

This property is incredibly useful and has been harnessed in various industries. In the food industry, it's used to improve texture and consistency, while in biotechnology, it serves as a medium for growing cellular cultures. What's particularly fascinating is that alginates, salts of alginic acid, can form different textures based on the cations present; for example, sodium alginate forms a gooey gel, whereas calcium alginate results in a more solid form. The versatility of alginates exemplifies the importance of understanding anionic polysaccharides in applied sciences.

Algae Types

Diving into the world of algae reveals a surprising diversity of forms and functions. Algae are photosynthetic organisms that range from microscopic, single-celled phytoplankton to large, multicellular forms like seaweeds. Broadly, algae can be categorized into several types, each with distinct features, habitats, and ecological roles.

For instance,

Microalgae

are tiny, often unicellular organisms that play a crucial role as the base of the aquatic food chain.

Green algae

are found in both freshwater and marine environments and are close relatives of land plants.

Red algae

, with their rich pigmentation due to phycobilins, primarily inhabit marine ecosystems and contribute to coral reef formations with their calcium carbonate structures.

Brown algae

, as discussed earlier, are notable for their size and the production of alginic acid. Understanding these variations is not only fascinating from a biological perspective but also critical for environmental conservation and commercial applications.