{"id":224579,"date":"2025-06-03T09:35:48","date_gmt":"2025-06-03T09:35:48","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=224579"},"modified":"2025-06-03T09:35:50","modified_gmt":"2025-06-03T09:35:50","slug":"what-molecule-is-indicated-by-the-letter-d","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/03\/what-molecule-is-indicated-by-the-letter-d\/","title":{"rendered":"What molecule is indicated by the letter D"},"content":{"rendered":"\n<p>What molecule is indicated by the letter D? Electrons carried via NADH Electrons carried via NADH and FADH2 A B C Glucose Pyruvate Cytosol O ATP O oxygen O water O pyruvate O glucose Mitochondrion D E CO2 CO2 ATP<\/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 molecule indicated by the letter <strong>D<\/strong> is <strong>oxygen (O\u2082)<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Explanation <\/strong><\/h3>\n\n\n\n<p>In cellular respiration, glucose is broken down in a series of steps to produce ATP, the energy currency of the cell. This process occurs in three main stages: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Glycolysis<\/strong> occurs in the <strong>cytosol<\/strong>, where <strong>glucose<\/strong> is broken down into <strong>pyruvate<\/strong>, producing a small amount of ATP and <strong>NADH<\/strong>.<\/li>\n\n\n\n<li>The <strong>pyruvate<\/strong> is transported into the <strong>mitochondrion<\/strong>, where it is further processed in the <strong>citric acid cycle<\/strong>, releasing <strong>CO\u2082<\/strong>, generating <strong>ATP<\/strong>, and producing more <strong>NADH<\/strong> and <strong>FADH\u2082<\/strong>.<\/li>\n\n\n\n<li>These reduced electron carriers (<strong>NADH<\/strong> and <strong>FADH\u2082<\/strong>) then donate electrons to the <strong>electron transport chain (ETC)<\/strong>, which is embedded in the inner mitochondrial membrane. As electrons move through the chain (from A to B to C), they power the pumping of protons into the intermembrane space, creating a proton gradient.<\/li>\n\n\n\n<li>At the <strong>end of the electron transport chain<\/strong>, electrons must be accepted by a final molecule to prevent backup in the chain. This final <strong>electron acceptor<\/strong> is <strong>oxygen (O\u2082)<\/strong>, the molecule labeled <strong>D<\/strong>. Oxygen combines with the electrons and hydrogen ions (protons) to form <strong>water (H\u2082O)<\/strong>. O2+4e\u2212+4H+\u21922H2OO\u2082 + 4e\u207b + 4H\u207a \u2192 2H\u2082O<\/li>\n<\/ol>\n\n\n\n<p>Without <strong>oxygen<\/strong>, the electron transport chain would halt, ATP production via oxidative phosphorylation would stop, and cells would have to rely on less efficient anaerobic processes.<\/p>\n\n\n\n<p>Thus, <strong>oxygen (D)<\/strong> is crucial because it <strong>accepts electrons<\/strong> at the end of the chain, enabling continued operation of the ETC and efficient ATP production. This role makes oxygen vital to aerobic respiration and energy metabolism in most eukaryotic cells.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner7-111.jpeg\" alt=\"\" class=\"wp-image-224580\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>What molecule is indicated by the letter D? Electrons carried via NADH Electrons carried via NADH and FADH2 A B C Glucose Pyruvate Cytosol O ATP O oxygen O water O pyruvate O glucose Mitochondrion D E CO2 CO2 ATP The Correct Answer and Explanation is: The molecule indicated by the letter D is oxygen [&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-224579","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/224579","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=224579"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/224579\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=224579"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=224579"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=224579"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}