Direction for: In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as
Assertion: Eukaryotic cells have the ability to adopt a variety of shapes and carry out directed movements. Reason: There are three principal types of protein filaments-actin filament, microtubules and intermediate filaments, which constitute the cytoskeletonA) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
C) If assertion is true statement but reason is false.
D) If both assertion and reason are false.
Correct Answer: A
Solution :
Eukaryotic cells (particularly animal and lower plant cells) have the ability to adopt a variety of shapes and carry out directed movements because they have a network of protein fibres that support the shape of the cell and anchor organelles to fixed location. This network is called cytoskeleton. Later is made up of: actin filaments, which are made of two strands of the fibrous protein twisted together and usually ocur in bundles Actin filaments are ubiquitous, and are concentrated below the plasma membrane in bundles known as stress fibres, which may have a contractile function, Microtubules, which are composed of 13 stacks of tubulin protein subunits arranged side by side to foqri a tube. Microtubules are comparatively stiff cytoskeletal elements that serve to organize metabolism and intracellular transport in the non-dividing cell, Intermediate filaments, which are composed of overlapping staggered tetramers of protein. This molecular arrangement allows for a rope like structure that imparts tremendous mechanical strength to the cell.
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