52. Which one of the following combinations signify similar function?
(a) Cryptochrome and flurochrome
(b) Cryptochrome and phytochrome
(c) Cytochrome and cryptochrome
(d) Fluorochrome and cytochrome

Introduction

Light is a key environmental cue that influences many biological processes in plants and animals. Various proteins are involved in detecting and responding to light signals. Among these, cryptochrome and phytochrome are two important light-sensitive proteins that play crucial roles in biological systems. Understanding their functions and how they are related can shed light on how organisms adapt to changing light conditions.

What Are Cryptochromes and Phytochromes?

• Cryptochromes are a family of flavoproteins that play a role in regulating circadian rhythms and light-mediated processes in plants and animals. In plants, they help with light sensing and timing, while in animals, they are involved in controlling the biological clock.

• Phytochromes, on the other hand, are photoreceptor proteins found in plants that detect light in the red and far-red spectrum. They are involved in regulating plant growth, germination, and flowering in response to light.

Comparing the Functions of Cryptochromes and Phytochromes

While cryptochromes and phytochromes are involved in light perception, their functions are distinct yet complementary in some contexts, particularly in plants:

• Cryptochrome: These proteins are mainly involved in blue light detection and circadian rhythm regulation. They influence processes like seed germination, growth, and responses to environmental light changes.

• Phytochrome: These proteins mainly detect red and far-red light and are integral to regulating processes like seedling development, flowering, and shade avoidance.

Despite their different light absorption properties, both cryptochromes and phytochromes serve as photoreceptors, enabling plants to respond appropriately to light cues and environmental changes.

Analyzing the Options

• (a) Cryptochrome and Fluorochrome: Not similar. Fluorochromes are dyes that fluoresce when exposed to light, often used in microscopy. They do not have biological functions like cryptochromes, which are involved in circadian rhythm regulation and light response.

• (b) Cryptochrome and Phytochrome: Similar. Both cryptochromes and phytochromes are light-sensitive proteins that enable organisms to respond to changes in light conditions. They work together in plants to regulate growth, development, and circadian rhythms.

• (c) Cytochrome and Cryptochrome: Not similar. Cytochromes are enzymes involved in electron transport and energy production, while cryptochromes are involved in light perception and circadian rhythm regulation.

• (d) Fluorochrome and Cytochrome: Not similar. As mentioned, fluorochromes are fluorescent dyes, and cytochromes are involved in cellular respiration and energy transfer. These two molecules serve entirely different functions in biological systems.

Conclusion

The correct answer is (b) Cryptochrome and Phytochrome. Both are light-sensitive proteins involved in regulating various light-dependent processes in plants and animals, although they respond to different types of light and are involved in distinct biological functions.

Correct Answer: (b) Cryptochrome and Phytochrome