{"id":221872,"date":"2025-05-30T16:15:58","date_gmt":"2025-05-30T16:15:58","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=221872"},"modified":"2025-05-30T16:16:00","modified_gmt":"2025-05-30T16:16:00","slug":"cellular-respiration-is-a-process-that-requires-oxygen-aerobic-conditions","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/30\/cellular-respiration-is-a-process-that-requires-oxygen-aerobic-conditions\/","title":{"rendered":"Cellular respiration is a process that requires oxygen (aerobic conditions)."},"content":{"rendered":"\n<p>Cellular respiration is a process that requires oxygen (aerobic conditions). However, many cell types and organisms can carry out energy metabolism when oxygen isn&#8217;t available (anaerobic conditions). Given this which of the following is true? a. Under anaerobic conditions the citric acid cycle will be run but oxidative phosphorylation will not be run. b. Under anaerobic conditions NADH must be recycled back to NAD+which can happen within the citric acid cycle. c. In animal cells, and some bacteria, pyruvate can be converted to lactate in order to regenerate NAD+that is needed to run glycolysis. d. Fermentation can only lead to the production of ethanol and CO2? as seen in yeast. e. Glycolysis cannot be run under anaerobic conditions.<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-1-color\">The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n<p>The correct answer is:<br><strong>c. In animal cells, and some bacteria, pyruvate can be converted to lactate in order to regenerate NAD\u207a that is needed to run glycolysis.<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation<\/h3>\n\n\n\n<p>Cellular respiration is the process by which cells extract energy from glucose. Under <strong>aerobic conditions<\/strong> (presence of oxygen), this process involves <strong>glycolysis<\/strong>, the <strong>citric acid cycle<\/strong> (also known as the Krebs cycle), and <strong>oxidative phosphorylation<\/strong>. However, when oxygen is not available (<strong>anaerobic conditions<\/strong>), cells cannot use the citric acid cycle and oxidative phosphorylation effectively, as both rely on oxygen directly or indirectly.<\/p>\n\n\n\n<p>Under anaerobic conditions, <strong>glycolysis<\/strong> still occurs and serves as the primary method of ATP production. During glycolysis, glucose is broken down into two molecules of <strong>pyruvate<\/strong>, generating a small amount of ATP and reducing <strong>NAD\u207a to NADH<\/strong>. However, if oxygen is not present to accept electrons during oxidative phosphorylation, NADH cannot be converted back to NAD\u207a through the electron transport chain.<\/p>\n\n\n\n<p>To continue glycolysis (which requires NAD\u207a), cells must find an alternative way to regenerate NAD\u207a from NADH. In <strong>animal cells and some bacteria<\/strong>, this is achieved through <strong>lactic acid fermentation<\/strong>, in which <strong>pyruvate is reduced to lactate<\/strong> by lactate dehydrogenase. This reaction <strong>oxidizes NADH to NAD\u207a<\/strong>, allowing glycolysis to continue producing ATP anaerobically.<\/p>\n\n\n\n<p>This makes option <strong>(c)<\/strong> the correct answer.<\/p>\n\n\n\n<p>Let&#8217;s briefly look at why the other options are incorrect:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>(a)<\/strong> is incorrect: The citric acid cycle also indirectly depends on oxygen because it needs NAD\u207a and FAD regenerated by the electron transport chain, which only functions in the presence of oxygen.<\/li>\n\n\n\n<li><strong>(b)<\/strong> is incorrect: NAD\u207a regeneration cannot happen within the citric acid cycle under anaerobic conditions.<\/li>\n\n\n\n<li><strong>(d)<\/strong> is incorrect: Fermentation does not only lead to ethanol and CO\u2082; <strong>lactic acid fermentation<\/strong> is another pathway.<\/li>\n\n\n\n<li><strong>(e)<\/strong> is incorrect: Glycolysis <strong>can<\/strong> occur under anaerobic conditions\u2014it is the main anaerobic ATP-producing pathway.<\/li>\n<\/ul>\n\n\n\n<p>Thus, <strong>option (c)<\/strong> accurately reflects how cells adapt to anaerobic conditions.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/05\/learnexams-banner5-141.jpeg\" alt=\"\" class=\"wp-image-221873\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Cellular respiration is a process that requires oxygen (aerobic conditions). However, many cell types and organisms can carry out energy metabolism when oxygen isn&#8217;t available (anaerobic conditions). Given this which of the following is true? a. Under anaerobic conditions the citric acid cycle will be run but oxidative phosphorylation will not be run. b. Under [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-221872","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/221872","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=221872"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/221872\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=221872"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=221872"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=221872"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}