{"id":4675,"date":"2025-07-24T02:43:43","date_gmt":"2025-07-24T02:43:43","guid":{"rendered":"https:\/\/schools.jove.com\/?p=4675"},"modified":"2026-07-22T15:40:49","modified_gmt":"2026-07-22T15:40:49","slug":"dark-reactions-teaching-the-second-stage-of-photosynthesis","status":"publish","type":"post","link":"https:\/\/schools.jove.com\/dark-reactions-teaching-the-second-stage-of-photosynthesis\/","title":{"rendered":"What Are Dark Reactions? Explaining the Second Stage of Photosynthesis"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"4675\" class=\"elementor elementor-4675\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ef3dc91 e-flex e-con-boxed e-con e-parent\" data-id=\"ef3dc91\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-081d7dd elementor-widget elementor-widget-heading\" data-id=\"081d7dd\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h1 class=\"elementor-heading-title elementor-size-default\">What Are Dark Reactions? Explaining the Second Stage of Photosynthesis\n<\/h1>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-7090152 e-flex e-con-boxed e-con e-parent\" data-id=\"7090152\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-44ee0c2 elementor-widget elementor-widget-text-editor\" data-id=\"44ee0c2\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.jove.com\/schools\/v\/19617\/dark-reactions\"><span style=\"font-weight: 400;\">dark reactions<\/span><\/a><span style=\"font-weight: 400;\"> \u2014 also known as the Calvin Cycle \u2014 are the second stage of the photosynthesis process. They don\u2019t need sunlight directly, but they rely on the energy created during the light reactions.\u00a0 This is the part of <\/span><a href=\"https:\/\/www.jove.com\/schools\/v\/19022\/cellular-respiration-and-photosynthesis\"><span style=\"font-weight: 400;\">photosynthesis<\/span><\/a><span style=\"font-weight: 400;\"> where plants use carbon dioxide from the air to build glucose \u2014 real plant food!<\/span><\/p><p><span style=\"font-weight: 400;\">When teaching this concept in <\/span><a href=\"https:\/\/www.jove.com\/schools\/solutions\/middle-school\/\"><span style=\"font-weight: 400;\">middle school<\/span><\/a><span style=\"font-weight: 400;\"> science, it\u2019s helpful to show how plants turn invisible gases into something tangible using energy captured from light.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-e308475 e-flex e-con-boxed e-con e-parent\" data-id=\"e308475\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-6d91503 elementor-widget elementor-widget-heading\" data-id=\"6d91503\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">How to Teach Dark Reactions in Middle School\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f8aa59f e-flex e-con-boxed e-con e-parent\" data-id=\"f8aa59f\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-1e1dcc5 elementor-widget elementor-widget-text-editor\" data-id=\"1e1dcc5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">To teach dark reactions in middle school, begin with this big idea:<\/span><span style=\"font-weight: 400;\"><br \/><\/span><a href=\"https:\/\/www.jove.com\/schools\/v\/19617\/dark-reactions\"><span style=\"font-weight: 400;\">Dark reactions <\/span><\/a><span style=\"font-weight: 400;\">use ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) from the light reactions along with carbon dioxide to make glucose.<\/span><\/p><p><span style=\"font-weight: 400;\">Key points for students:<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">These reactions occur in the stroma of the chloroplast.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">They use energy, not light, so they can happen day or night.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">The process is called the Calvin Cycle. It\u2019s a repeating system that builds sugar molecules.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><\/ul><p><a href=\"https:\/\/www.jove.com\/schools\/science-video\/\"><span style=\"font-weight: 400;\">JoVE\u2019s science videos<\/span><\/a><span style=\"font-weight: 400;\"> illustrate how ATP and NADPH are \u2018spent\u2019 to convert carbon into something useful: glucose, the plant\u2019s energy source.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-a657b98 e-flex e-con-boxed e-con e-parent\" data-id=\"a657b98\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e0b5642 elementor-widget elementor-widget-heading\" data-id=\"e0b5642\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Calvin Cycle Classroom Activity\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-6a691d6 e-flex e-con-boxed e-con e-parent\" data-id=\"6a691d6\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-3bfad8d elementor-widget elementor-widget-text-editor\" data-id=\"3bfad8d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><b>Activity:<\/b><span style=\"font-weight: 400;\"> Carbon Conversion Relay<\/span><\/p><p><b>Materials:<\/b><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Index cards labeled with CO\u2082, ATP, NADPH, Glucose<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Chart of the Calvin Cycle steps<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><\/ul><p><b>Instructions:<\/b><\/p><ol><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Create small student teams.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Students race to collect cards in the correct order to complete the cycle.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">After each round, discuss which molecules are inputs and outputs.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><\/ol><p><span style=\"font-weight: 400;\">This kinesthetic activity reinforces that the dark reactions are a step-by-step process \u2014 not a random mix. It also helps students remember which parts come from the light reactions.<\/span><\/p><p><span style=\"font-weight: 400;\">To support this,<\/span><a href=\"https:\/\/www.jove.com\/schools\/v\/19617\/dark-reactions\"><span style=\"font-weight: 400;\"> JoVE\u2019s Dark Reactions video<\/span><\/a><span style=\"font-weight: 400;\"> clearly shows how ATP and NADPH are used to turn carbon dioxide into glucose inside the chloroplast stroma.<\/span><\/p><p><span style=\"font-weight: 400;\">You can also revisit <\/span><a href=\"https:\/\/www.jove.com\/schools\/v\/19019\/light-reactions\"><span style=\"font-weight: 400;\">JoVE\u2019s Light Reactions<\/span><\/a><span style=\"font-weight: 400;\"> video before this activity to remind students where the energy molecules (ATP and NADPH) come from.<\/span><\/p><p><span style=\"font-weight: 400;\">These videos offer a visual step-by-step guide that pairs perfectly with the relay, making the Calvin Cycle easier to grasp through movement and repetition.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-aba150d e-flex e-con-boxed e-con e-parent\" data-id=\"aba150d\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-4a03b32 elementor-widget elementor-widget-heading\" data-id=\"4a03b32\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Difference Between Light and Dark Reactions\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-3b2cf0b e-flex e-con-boxed e-con e-parent\" data-id=\"3b2cf0b\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9fe7b31 elementor-widget elementor-widget-text-editor\" data-id=\"9fe7b31\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Students often mix up these two processes. Here\u2019s a quick comparison to help clarify:<\/span><\/p><table><tbody><tr><td><p><b>Aspect<\/b><\/p><\/td><td><p><b>Light Reactions<\/b><\/p><\/td><td><p><b>Dark Reactions (Calvin Cycle)<\/b><\/p><\/td><\/tr><tr><td><p><span style=\"font-weight: 400;\">Location<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Thylakoid membranes in chloroplasts<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Stroma of chloroplasts<\/span><\/p><\/td><\/tr><tr><td><p><span style=\"font-weight: 400;\">Requires light<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Yes<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">No (uses stored energy)<\/span><\/p><\/td><\/tr><tr><td><p><span style=\"font-weight: 400;\">Main inputs<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Sunlight, water<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">CO\u2082, ATP, NADPH<\/span><\/p><\/td><\/tr><tr><td><p><span style=\"font-weight: 400;\">Main outputs<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Oxygen, ATP, NADPH<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Glucose (sugar)<\/span><\/p><\/td><\/tr><tr><td><p><span style=\"font-weight: 400;\">Energy role<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Creates energy<\/span><\/p><\/td><td><p><span style=\"font-weight: 400;\">Uses energy<\/span><\/p><\/td><\/tr><\/tbody><\/table><p><a href=\"https:\/\/www.jove.com\/schools\/science-video\/concept-video\/\"><span style=\"font-weight: 400;\">JoVE\u2019s concept videos<\/span><\/a><span style=\"font-weight: 400;\"> make this table come alive with visuals showing how these reactions happen inside plant cells.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-320f98c e-flex e-con-boxed e-con e-parent\" data-id=\"320f98c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c53539f elementor-widget elementor-widget-heading\" data-id=\"c53539f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Carbon Fixation in Plants Explained Simply\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-0cb18b5 e-flex e-con-boxed e-con e-parent\" data-id=\"0cb18b5\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-4e8f445 elementor-widget elementor-widget-text-editor\" data-id=\"4e8f445\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Carbon fixation may sound complex, but it just means plants take carbon from the air and \u2018fix\u2019 it into solid glucose. This is how plants grow!<\/span><\/p><p><span style=\"font-weight: 400;\">Use this analogy:<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Imagine CO\u2082 as puzzle pieces floating in the air.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">The Calvin Cycle \u201cgrabs\u201d them and connects them into a solid object \u2014 glucose.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">That glucose becomes part of leaves, stems, and fruits.<\/span><span style=\"font-weight: 400;\"><br \/><br \/><\/span><\/li><\/ul><p><span style=\"font-weight: 400;\">Show students how plants are carbon-capturing machines, turning invisible gas into real matter.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-dc639eb e-flex e-con-boxed e-con e-parent\" data-id=\"dc639eb\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9c6baf1 elementor-widget elementor-widget-heading\" data-id=\"9c6baf1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Conclusion: Teaching Dark Reactions Visually\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-22e2aa1 e-flex e-con-boxed e-con e-parent\" data-id=\"22e2aa1\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e3f33ee elementor-widget elementor-widget-text-editor\" data-id=\"e3f33ee\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><a href=\"https:\/\/www.jove.com\/schools\/v\/19617\/dark-reactions\"><span style=\"font-weight: 400;\">Dark reactions<\/span><\/a><span style=\"font-weight: 400;\"> are essential for understanding how plants store energy and grow. With <\/span><a href=\"https:\/\/www.jove.com\/schools\/solutions\/\"><span style=\"font-weight: 400;\">JoVE\u2019s solutions <\/span><\/a><span style=\"font-weight: 400;\">and simple classroom models, students can see how the Calvin Cycle fuels life.<\/span><\/p><p><a href=\"https:\/\/share.hsforms.com\/1FyaUdqz3T3yuF-IuUZXDfwc2eur\"><span style=\"font-weight: 400;\">Book a Free Demo<\/span><\/a><span style=\"font-weight: 400;\"> to explore JoVE\u2019s visual lessons on photosynthesis and plant biology.<\/span><span style=\"font-weight: 400;\"><br \/><\/span><span style=\"font-weight: 400;\">Bring JoVE to your classroom starting at just $2 per student.*<\/span><\/p><p><span style=\"font-weight: 400;\"><br \/><\/span><span style=\"font-weight: 400;\">*Pricing based on 1,500 students.\u00a0<\/span><\/p><p><span style=\"font-weight: 400;\">(<\/span><a href=\"https:\/\/viewmail.jove.com\/hubfs\/K12%20Schools\/K12%20Funding%20Resources%20Flyer_2025.pdf?utm_campaign=14083630-K12_Q2_2025_Newsletter_June%20Edition&amp;utm_medium=email&amp;_hsenc=p2ANqtz-_YoAQE_jZOxP2S56v0c7u1QwdSYCTxqWB2w5XzInlBixw8VciDctvVLnjRYMcQLUwoIc0yUBDE6qXfTZ_fdpwkm9LHPA&amp;_hsmi=2&amp;utm_content=2&amp;utm_source=hs_email\"><span style=\"font-weight: 400;\">Explore funding options here<\/span><\/a><span style=\"font-weight: 400;\">)<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>What Are Dark Reactions? Explaining the Second Stage of Photosynthesis The dark reactions \u2014 also known as the Calvin Cycle [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":4676,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"content-type":"","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":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-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":"","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-4)","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-4)","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-4)","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":[63],"tags":[],"class_list":["post-4675","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ngss-standards"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.8 (Yoast SEO v27.8) - 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