Problem 137 - Objective Biology for NEET

Question

Select the incorrect statement: (a) The chloroplast contains chlorophyll and carotenoid pigments. (b) Chromoplast contains water soluble carotenoid pigments like carotene, xanthophylls. (c) Plastid is easily observed under microscope. (d) Chloroplast is a double membrane bound organelle.

Step-by-Step Solution

Answer

The incorrect statement is (b): Chromoplast contains water soluble carotenoid pigments like carotene, xanthophylls.

Step 1: Evaluate statement (a)

The chloroplast is known to contain chlorophyll and carotenoid pigments which are important for the various functions it performs, particularly photosynthesis. Therefore, statement (a) is correct.

Step 2: Evaluate statement (b)

Chromoplasts contain carotenoid pigments like carotene and xanthophylls but these pigments are not water soluble. Therefore, statement (b) is incorrect. This is the incorrect statement.

Step 3: Evaluate statement (c)

Plastid is a cellular organelle that is indeed easily observed under a microscope. Therefore, statement (c) is correct.

Step 4: Evaluate statement (d)

Chloroplasts are indeed double membrane-bound organelles. Therefore, statement (d) is correct.

Key Concepts

Chloroplast Structure

The chloroplast is an essential cell organelle found in plant cells and eukaryotic algae, playing a crucial role in the process of photosynthesis. It is characterized by a unique double membrane-bound structure.

Inside the chloroplast, the most prominent features include thylakoids, which are small disc-like compartments stacked into structures known as grana. These stacked thylakoids are interconnected by lamellae, often referred to as the stroma lamellae. The space surrounding the thylakoids is the aqueous matrix called the stroma, which contains the enzymes necessary for the synthesis of organic molecules, DNA, ribosomes, and various other substances.

The chloroplasts' membranes are integral to maintaining a differential environment, which is key to the conversion of light energy into chemical energy during photosynthesis. This unique architecture not only optimizes the process of light absorption through the chlorophyll and other pigments located in the thylakoid membranes but also helps in the generation of ATP, the energy currency of the cell.

Chromoplast Pigments

Chromoplasts are a type of plastid renowned for their vibrant colors, which come from the storage of unique pigments known as carotenoids. These pigments include carotene, which provides the orange color, and xanthophylls, which are responsible for the yellow coloration in many fruits, flowers, and autumn leaves.

Despite a common misconception, carotenoids are not water-soluble; instead, they are fat-soluble, meaning they require fats or oils to dissolve adequately. They play significant roles not only in the colors they impart but also in attracting pollinators and seed dispersers, as well as in protecting the photosynthetic apparatus from damage by absorbing certain wavelengths of light. Additionally, they are precursors to important biological molecules, such as the hormone abscisic acid and vitamin A, which is essential for vision in animals, including humans.

Plastid Observation

Plastids, including chloroplasts, chromoplasts, and leucoplasts, can be observed through various forms of microscopy due to their substantial size in comparison to other cellular components. Under a light microscope, chloroplasts can often be seen as green structures inside plant cells because of their chlorophyll content, usually moving along the cell walls. This movement, called cytoplasmic streaming, can be particularly engaging to observe.

For a more detailed observation, transmission electron microscopy (TEM) can be used to view the fine structure of plastids, which reveals the internal organization, such as the thylakoid membranes in chloroplasts. Studying plastids under the microscope provides students with real insights into cell biology, emphasizing the importance of these organelles' functions in plants' and algae's life processes.