Question

Which of the following statements regarding cilia is not correct -

• A. The organized beating of cilia is controlled by fluxes of Ca${}^{2+}$ across the membrane
• B. Cilia are hair-like cellular appendages
• C. Microtubules of cilia are composed of tubulin
• D. Cilin contain an outer ring of nine doublet microtubules surrounding two single microtubules

Answer 1

The correct option is A The organized beating of cilia is controlled by fluxes of Ca${}^{2+}$ across the membrane

Cilia are fine hair-like vibratile, cytoplasmic processes borne by certain cell types. Their movement either propel the organism or move the medium past a fixed cell. The cilia are enclosed by a unit membrane which is an extension of the plasma membrane of the cell. Within the membrane, is a fluid matrix having a supporting axial shaft, or axoneme. The axoneme is composed of eleven microtubules. Two microtubules are single and lie at the centre with a gap in-between. They are called central singlets. The remaining nine microtubules are double and lie in a ring around the central microtubules. The two microtubules forming a doublet are named A and B subtubules. The microtubules, single as well as double, are composed of the globular units of the protein tubulin. The arms of A microtubules contain protein dynein. The latter is ATPase enzyme which catalyzes the hydrolysis of ATP to ADP and transfers the free energy released directly to ciliary work.

So, the correct answer is 'The organized beating of cilia is controlled by fluxes of Ca2+ across the membrane'.