{"id":187316,"date":"2025-02-04T06:25:52","date_gmt":"2025-02-04T06:25:52","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=187316"},"modified":"2025-02-04T06:25:54","modified_gmt":"2025-02-04T06:25:54","slug":"which-of-the-following-best-describes-the-changes-in-cell-volume-that-will-occur","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/02\/04\/which-of-the-following-best-describes-the-changes-in-cell-volume-that-will-occur\/","title":{"rendered":"Which of the following best describes the changes in cell volume that will occur"},"content":{"rendered":"\n

Which of the following best describes the changes in cell volume that will occur when red blood cells (previously equilibrated in a 280-milliosmolar solution of NaCl) are placed in a solution of 140-millimolar NaCl containing 20-millimolar urea, a relatively large but permeant molecule?<\/p>\n\n\n\n

A) Shrink, then swell and lyse<\/p>\n\n\n\n

B) Shrink, then return to original volume<\/p>\n\n\n\n

C) Swell and lyse<\/p>\n\n\n\n

D) Swell, then return to original volume<\/p>\n\n\n\n

E) No change in cell volume<\/p>\n\n\n\n

The Correct Answer and Explanation is :<\/strong><\/mark><\/p>\n\n\n\n

Correct Answer: A) Shrink, then swell and lyse<\/strong><\/h3>\n\n\n\n

Explanation:<\/strong><\/h3>\n\n\n\n

Red blood cells (RBCs) are highly sensitive to osmotic changes in their environment. The tonicity of the solution determines how water moves across the RBC membrane.<\/p>\n\n\n\n

    \n
  1. Initial Shrinkage Due to Hypertonicity:<\/strong><\/li>\n<\/ol>\n\n\n\n
      \n
    • The RBCs are initially equilibrated in a 280-milliosmolar (mOsm) NaCl solution, which is isotonic to them.<\/li>\n\n\n\n
    • The new solution contains 140 mM NaCl<\/strong> and 20 mM urea<\/strong>.<\/li>\n\n\n\n
    • Since NaCl dissociates into Na\u207a and Cl\u207b<\/strong>, the total osmolarity from NaCl is 140 \u00d7 2 = 280 mOsm<\/strong>, making it isotonic in terms of total osmolarity.<\/li>\n\n\n\n
    • However, urea is a permeant molecule<\/strong>, meaning it can cross the RBC membrane.<\/li>\n\n\n\n
    • Initially, urea is absent inside the cell, so it does not contribute to the tonicity at the moment of exposure.<\/li>\n\n\n\n
    • The external environment is effectively hypertonic<\/strong> in terms of non-permeant solutes (NaCl)<\/strong>, causing water to leave the RBC, leading to cell shrinkage<\/strong>.<\/li>\n<\/ul>\n\n\n\n
        \n
      1. Delayed Swelling Due to Urea Influx:<\/strong><\/li>\n<\/ol>\n\n\n\n
          \n
        • Over time, urea equilibrates across the membrane<\/strong>, entering the RBC and increasing intracellular osmolarity.<\/li>\n\n\n\n
        • Once urea reaches equilibrium, the intracellular osmolarity increases<\/strong>, reducing the effective hypertonicity of the extracellular fluid.<\/li>\n\n\n\n
        • Water re-enters the RBC, causing cell swelling<\/strong>.<\/li>\n<\/ul>\n\n\n\n
            \n
          1. Lysis Due to Overhydration:<\/strong><\/li>\n<\/ol>\n\n\n\n
              \n
            • Since urea freely diffuses into the RBC but does not contribute to tonicity outside, water influx continues beyond the initial volume, leading to cell swelling and eventual lysis<\/strong>.<\/li>\n<\/ul>\n\n\n\n

              Thus, the RBCs will initially shrink due to water loss, then swell due to urea influx, and ultimately lyse due to excessive water entry.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

              Which of the following best describes the changes in cell volume that will occur when red blood cells (previously equilibrated in a 280-milliosmolar solution of NaCl) are placed in a solution of 140-millimolar NaCl containing 20-millimolar urea, a relatively large but permeant molecule? A) Shrink, then swell and lyse B) Shrink, then return to original […]<\/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-187316","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/187316","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=187316"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/187316\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=187316"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=187316"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=187316"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}