{"id":84758,"date":"2025-06-01T02:49:12","date_gmt":"2025-06-01T02:49:12","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=84758"},"modified":"2025-06-01T02:49:12","modified_gmt":"2025-06-01T02:49:12","slug":"a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/","title":{"rendered":"A protein is synthesized in the endoplasmic reticulum bound ribosomes"},"content":{"rendered":"

A protein is synthesized in the endoplasmic reticulum bound ribosomes and it targets to the inner thylakoid space of chloroplast. How many double-layered membrane layers it has to pass to reach its destination?<\/p>\n

[amp_mcq option1=”2″ option2=”3″ option3=”4″ option4=”5″ correct=”option3″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC CDS-1 – 2018<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nThe protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers:
\n1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer).
\n2. Crossing the outer chloroplast membrane (1 layer).
\n3. Crossing the inner chloroplast membrane (1 layer).
\n4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer).
\nTotal membrane layers crossed = 1 + 1 + 1 + 1 = 4.
\n<\/section>\n
\nReaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.
\n<\/section>\n
\nThe standard pathway for most chloroplast proteins is synthesis on free ribosomes in the cytoplasm followed by post-translational import. The mention of synthesis on ER-bound ribosomes implies a non-standard or specific targeting route, or potentially release from the ER system into the cytoplasm before import. Chloroplasts have a double membrane envelope (outer and inner membranes) and an internal thylakoid membrane system.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

A protein is synthesized in the endoplasmic reticulum bound ribosomes and it targets to the inner thylakoid space of chloroplast. How many double-layered membrane layers it has to pass to reach its destination? [amp_mcq option1=”2″ option2=”3″ option3=”4″ option4=”5″ correct=”option3″] This question was previously asked in UPSC CDS-1 – 2018 Download PDFAttempt Online The protein is … <\/p>\n

Detailed SolutionA protein is synthesized in the endoplasmic reticulum bound ribosomes<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1087],"tags":[1114,1117,1152],"class_list":["post-84758","post","type-post","status-publish","format-standard","hentry","category-upsc-cds-1","tag-1114","tag-biology","tag-cell","no-featured-image-padding"],"yoast_head":"\nA protein is synthesized in the endoplasmic reticulum bound ribosomes<\/title>\n<meta name=\"description\" content=\"The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers: 1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer). 2. Crossing the outer chloroplast membrane (1 layer). 3. Crossing the inner chloroplast membrane (1 layer). 4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer). Total membrane layers crossed = 1 + 1 + 1 + 1 = 4. Reaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"A protein is synthesized in the endoplasmic reticulum bound ribosomes\" \/>\n<meta property=\"og:description\" content=\"The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers: 1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer). 2. Crossing the outer chloroplast membrane (1 layer). 3. Crossing the inner chloroplast membrane (1 layer). 4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer). Total membrane layers crossed = 1 + 1 + 1 + 1 = 4. Reaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T02:49:12+00:00\" \/>\n<meta name=\"author\" content=\"rawan239\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rawan239\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"A protein is synthesized in the endoplasmic reticulum bound ribosomes","description":"The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers: 1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer). 2. Crossing the outer chloroplast membrane (1 layer). 3. Crossing the inner chloroplast membrane (1 layer). 4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer). Total membrane layers crossed = 1 + 1 + 1 + 1 = 4. Reaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/","og_locale":"en_US","og_type":"article","og_title":"A protein is synthesized in the endoplasmic reticulum bound ribosomes","og_description":"The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers: 1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer). 2. Crossing the outer chloroplast membrane (1 layer). 3. Crossing the inner chloroplast membrane (1 layer). 4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer). Total membrane layers crossed = 1 + 1 + 1 + 1 = 4. Reaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T02:49:12+00:00","author":"rawan239","twitter_card":"summary_large_image","twitter_misc":{"Written by":"rawan239","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/","url":"https:\/\/exam.pscnotes.com\/mcq\/a-protein-is-synthesized-in-the-endoplasmic-reticulum-bound-ribosomes\/","name":"A protein is synthesized in the endoplasmic reticulum bound ribosomes","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T02:49:12+00:00","dateModified":"2025-06-01T02:49:12+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. 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