{"id":31661,"date":"2025-06-22T05:45:25","date_gmt":"2025-06-22T05:45:25","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=31661"},"modified":"2025-06-22T05:45:27","modified_gmt":"2025-06-22T05:45:27","slug":"which-of-the-following-is-true-of-microtubules-but-not-actin","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/which-of-the-following-is-true-of-microtubules-but-not-actin\/","title":{"rendered":"Which of the following is true of microtubules but not actin"},"content":{"rendered":"\n<p>Which of the following is true of microtubules but not actin? Select one: Microtubules are nucleated by proteins like Arp2\/3 and tormin. Microtubule subunits bind to and hydrolyze ATP. Microtubules are formed from multiple protofilaments in a cylindrical arrangement. Microtubules do not have plus or minus ends. Microtubules are involved in muscle contraction.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"700\" height=\"279\" src=\"https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/image-188.png\" alt=\"\" class=\"wp-image-31662\" srcset=\"https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/image-188.png 700w, https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/image-188-300x120.png 300w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\" \/><\/figure>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n<p>The correct answer is: <strong>Microtubules are formed from multiple protofilaments in a cylindrical arrangement.<\/strong><\/p>\n\n\n\n<p><strong>Explanation:<\/strong> Microtubules and actin filaments are both key components of the eukaryotic cytoskeleton, but they differ significantly in structure, function, and molecular composition.<\/p>\n\n\n\n<p>Microtubules are hollow tubes composed of \u03b1- and \u03b2-tubulin heterodimers. These dimers polymerize into linear chains known as protofilaments. Typically, thirteen protofilaments associate side-by-side to form a cylindrical tube. This highly ordered, symmetrical arrangement provides microtubules with the rigidity and structural integrity required for their cellular roles, such as vesicle transport, mitotic spindle formation, and organelle positioning.<\/p>\n\n\n\n<p>Actin filaments, by contrast, are composed of globular actin subunits that assemble into a helical polymer. They do not form cylindrical structures. Instead, actin filaments are thinner and more flexible, playing major roles in cell shape, motility, and processes like endocytosis and cytokinesis.<\/p>\n\n\n\n<p>The other answer choices are incorrect for the following reasons:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Arp2\/3 and formin are nucleation proteins associated with actin filaments, not microtubules. Microtubule nucleation is primarily mediated by the \u03b3-tubulin ring complex.<\/li>\n\n\n\n<li>Microtubule subunits bind to and hydrolyze GTP, not ATP. This GTP hydrolysis is important for dynamic instability, a hallmark of microtubule behavior.<\/li>\n\n\n\n<li>Microtubules possess structural polarity, having distinct plus and minus ends. This polarity is critical for directional motor protein movement and intracellular transport.<\/li>\n\n\n\n<li>Muscle contraction is primarily driven by interactions between actin filaments and myosin motors. Microtubules are not involved in generating contractile force in muscle cells.<\/li>\n<\/ul>\n\n\n\n<p>Recognizing the cylindrical arrangement of protofilaments as unique to microtubules helps distinguish them structurally from actin filaments, reinforcing their specialized roles within the cell<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"1024\" src=\"https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-194.jpeg\" alt=\"\" class=\"wp-image-31663\" srcset=\"https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-194.jpeg 1024w, https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-194-300x300.jpeg 300w, https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-194-150x150.jpeg 150w, https:\/\/gaviki.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-194-768x768.jpeg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Which of the following is true of microtubules but not actin? Select one: Microtubules are nucleated by proteins like Arp2\/3 and tormin. Microtubule subunits bind to and hydrolyze ATP. Microtubules are formed from multiple protofilaments in a cylindrical arrangement. Microtubules do not have plus or minus ends. Microtubules are involved in muscle contraction. The Correct [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-31661","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31661","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=31661"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31661\/revisions"}],"predecessor-version":[{"id":31664,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31661\/revisions\/31664"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=31661"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=31661"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=31661"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}