Cilia and Flagella

Topics: Cilium, Cytoskeleton, Cell Pages: 4 (1198 words) Published: May 24, 2014
Eukaryotic cells are present in organisms that contain cilia and flagella - organelles that function primarily for motility and also as a sensory reception. Both secondary cilia (motile) and flagella contain quite similar internal structures; while primary cilia (nonmotile) - found more commonly than secondary in common cells, have a deficiency of two singlet microtubules that together account for the cell’s lack of movement (Adams 2010). Mutation of cilia with such characteristics may lead to ciliary dysfunction, including polycystic kidney disease, which result due to the lack of polycystin-1 and polycystin-2 proteins, and also Bardet-Biedl syndrome, also from protein (BBS protein) deficiency. The repetitiveness of the beating of both cilia and flagella provide adequate, constant motility for all types of cells (Lindermann & Lesich 2010, p. 519). These organelles are ‘cellular appendages composed of specialised microtubules’ encased in an extension of a plasma membrane (Linck 2009, p. 1). The core of microtubules has remained unaltered throughout evolution since its origins. Cilia and flagella elongate from a basal body, which itself contains nine microtubule triplets, surrounding a cartwheel that operate as a basis for the assembly of the core structure (Vincensini, Bliscnick & Bastin 2012, p. 109). This core structure (called axoneme) within motile cilia and flagella consists the typical “9+2” arrangement where nine microtubule doublets are constructed as an outside ring and two microtubule singlets are centred within the doublets (Linck 2009, p. 1). Alternatively, the “9+0” axoneme present in primary cilia do not have sets of dynein arms, resulting in the lack of movement (Vincensini, Bliscnick & Bastin 2012, p. 109). According to Linck (2010, p. 3), ‘basal bodies and axonemes are assembled from over 250 different polypeptides, some shared by both organelles and many unique to each and another approximately 250 proteins comprise the membrane’. The protein...

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