Cell Biology: Structure of Cilia and Flagella

Structure of Cilia and Flagella

• Cilia and flagella are hair-like extensions of the cell membrane, crucial for cell motility.
• Eukaryotic flagella differ structurally from prokaryotic flagella.
• Both structures are covered by a plasma membrane with a core called the axoneme.
• The axoneme is characterized by a 9+2 arrangement: nine doublets of peripheral microtubules and two central microtubules.
• Peripheral doublets are interconnected by linkers, and central tubules are connected by radial spokes and enclosed by a central sheath.
• Cilia and flagella originate from basal bodies or blepharoplasts.

Microbodies

• Microbodies are single membrane-bound vesicles containing various enzymes.

Cell Definition and Types

• Cells are the structural and functional units of organisms.
• Unicellular organisms are composed of a single cell, while multicellular organisms consist of many cells.

Minimum Requirements for a Cell

• Essential components of a complete cell include: cell membrane, cytoplasm, and genetic material.
• Unicellular organisms can perform all vital life functions independently.

History of Cell Discovery

• First observed dead cells in cork by Robert Hooke.
• First living cells discovered by Anton Von Leeuwenhoek.
• Nucleus discovered by Robert Brown.

Cell Theory

• Formulated by Schleiden and Schwann, stating all living organisms are composed of cells and their products.
• Rudolf Virchow enhanced the theory by explaining that all cells arise from pre-existing cells, leading to modern cell theory.

Functions of Endoplasmic Reticulum (ER)

• Key functions include protein and lipid synthesis, intracellular transport, mechanical support, and detoxification.
• Facilitates formation of nuclear membrane, lysosomes, and microbodies.

Golgi Complex

• First observed by Camillo Golgi; also known as lipochondria or dictyosome in plants.
• Composed of cisternae (flattened structures), tubules (branched tube-like structures), and vesicles (membrane-bound structures).
• Functions in cell secretion, modification of macromolecules, and formation of lysosomes.

Chloroplast Structure and Function

• Surrounded by a double membrane: outer membrane is permeable; inner membrane is less permeable.
• Contains stroma, which houses thylakoids stacked in grana, and is essential for photosynthesis.
• Quantasome consists of pigment molecules within thylakoid membranes, playing a role in light absorption.
• Contains circular, GC-rich DNA and 70s ribosomes, indicating a semi-autonomous nature.

Biogenesis of Chloroplasts

• Chloroplasts can form from proplastids, indicating their ability to develop from precursor structures.
• They are described as semi-autonomous organelles due to their limited DNA and reliance on the cell's main DNA for protein synthesis.

Explore the intricate structures and functions of cilia and flagella in this quiz. Understand the differences between eukaryotic and prokaryotic flagella, as well as the importance of the axoneme's unique arrangement. Test your knowledge of microbodies and the essential characteristics of cells.