Problem 134 - Objective Biology for NEET

Question

Based on the type of pigments, the plastid can be classified into how many types? (a) 1 (b) 2 (c) 3 (d) 4

Step-by-Step Solution

Answer

The plastid can be classified into 3 types based on the type of pigments. So, the correct answer is (c) 3.

Step 1: Recall Plastid types

Plastids exist in different forms, each specialized for either the manufacture or storage of specific types of molecules. They are classified based on the pigments they have.

Step 2: List the Plastid types

Plastids are broadly classified into three types: 1. Chloroplasts: These contain chlorophyll, a green pigment necessary for photosynthesis. 2. Chromoplasts: These contain carotenoid pigments, which give plants' fruits and flowers their vibrant orange, yellow, and red colors.3. Leucoplasts: These are non-pigmented and are involved in the synthesis and storage of food.

Key Concepts

Chloroplasts

Chloroplasts are specialized organelles found in the cells of green plants and algae. They are the site of photosynthesis, the process by which plants convert sunlight into chemical energy. Within the chloroplasts, there are stacks of thylakoids, called grana, where chlorophyll, the green pigment, captures light energy.

Photosynthesis involves two main stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, sunlight is converted into chemical energy in the form of ATP and NADPH. The Calvin cycle, which takes place in the stroma of chloroplasts, uses this energy to synthesize glucose from carbon dioxide and water.

It's important to highlight that chloroplasts not only contribute to the green color of plants but are also essential for their growth and energy supply.

Chromoplasts

Chromoplasts are another type of plastids, which are mainly responsible for imparting color to fruits, flowers, and other parts of plants. These plastids contain pigments such as carotenoids, including beta-carotene (orange), lycopene (red), and xanthophylls (yellow).

Unlike chloroplasts, chromoplasts do not play a direct role in photosynthesis. However, the pigments they house are crucial for attracting pollinators to flowers and aiding in seed dispersal by enticing animals with colorful fruits. It's the transformation of chloroplasts into chromoplasts during fruit ripening that causes green tomatoes to turn red as they mature.

Leucoplasts

Leucoplasts are a group of non-pigmented plastids primarily involved in the synthesis and storage of starches, lipids, and proteins. They are generally found in non-photosynthetic tissues of plants such as roots, tubers, and seeds. Amyloplasts, a type of leucoplast, specifically store starch and can convert it back into sugar when the plant requires energy.

Due to their storage function, leucoplasts are essential for plant growth and development. When a seed germinates or a tuber grows into a new plant, it's the stored nutrients within leucoplasts that provide the necessary resources for this process.

Plant Pigments

Plant pigments are responsible for the multitude of colors we see in plants, serving various roles such as photosynthesis and attracting pollinators. The main types of pigments are chlorophylls, carotenoids, anthocyanins, and xanthophylls.

Chlorophyll, as mentioned earlier, is essential for photosynthesis and gives plants their green color. Carotenoids protect plant cells against damage from sunlight, provide yellow to red colors, and are also antioxidants. Anthocyanins are responsible for red, purple, and blue hues in plants and have a protective role against UV radiation. Xanthophylls are yellow pigments that also participate in photosynthesis.

• Chlorophyll: Green pigmentation for photosynthesis
• Carotenoids: Yellow to red pigmentation, photoprotection
• Anthocyanins: Red to blue pigmentation and UV protection
• Xanthophylls: Yellow pigmentation and involvement in photosynthesis

These pigments not only give plants their vibrant colors but also play crucial roles in their survival.