25. Membrane-bound, Golgi-derived structures containing proteolytic enzymes in sperms of sea urchin are called
    (1) cortical granules (2) micromeres
    (3) acrosomal vesicles (4) macromeres

The membrane-bound, Golgi-derived structures in sea urchin sperm that contain proteolytic enzymes are called acrosomal vesicles. These vesicles play a vital role during fertilization by undergoing the acrosome reaction, which involves their exocytosis to release enzymes that help the sperm penetrate the egg’s protective jelly coat and vitelline envelope.

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Introduction

Fertilization in sea urchins is a complex and highly regulated process involving precise molecular and cellular events. Central to this process is the acrosomal vesicle, a Golgi-derived, membrane-bound organelle in sperm that contains proteolytic enzymes necessary for breaking down the egg’s outer layers. Understanding the structure and function of these vesicles sheds light on mechanisms of sperm-egg interaction and fertilization success.

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What are Acrosomal Vesicles?

Acrosomal vesicles are specialized compartments derived from the Golgi apparatus during sperm development. Located at the anterior region of the sperm head, these vesicles contain hydrolytic enzymes such as hyaluronidase and acrosin, which facilitate the degradation of the protective layers around the egg.

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Role in Acrosome Reaction

The acrosome reaction is triggered when sperm contact the egg jelly or vitelline envelope. This leads to the fusion of the acrosomal vesicle membrane with the sperm plasma membrane, resulting in exocytosis of enzymatic contents. The released enzymes create a passageway through the extracellular matrix, allowing the sperm to reach and subsequently fuse with the egg plasma membrane.

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Differentiation from Other Terms

• Cortical granules are membrane-bound structures located in the egg cytoplasm, not sperm, which release their contents post-fertilization to prevent polyspermy.

• Micromeres and macromeres refer to specific cell types formed early in embryonic development and are unrelated to sperm structures.

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Biological Importance

The acrosomal vesicle’s enzymatic contents are critical for facilitating sperm penetration of the egg’s extracellular barriers. Without the proper function of these vesicles, fertilization cannot occur, marking them as essential organelles in reproductive biology.

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Conclusion

Acrosomal vesicles in sea urchin sperm are Golgi-derived, membrane-bound structures containing enzymes necessary for digesting the egg’s outer layers during fertilization. They enable the sperm to penetrate the egg extracellular matrix, leading to successful fertilization.

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This article highlights the importance of acrosomal vesicles in sea urchin fertilization, emphasizing their enzymatic role and membrane dynamics essential for reproductive success.

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Final answer:
(3) acrosomal vesicles