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GS Paper IUPSC Prelims 1998
Health & Medicine
Question No. 401Interactive Test Mode
00:00
+2-0.66

Q401. Which one of the following statements regarding starch and cellulose is not correct?

Which one of the following statements regarding starch and cellulose is not correct?

Select the correct option below (or cross out options to eliminate)
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Official Answer Key & Detailed Solution

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Official UPSC Answer KeyUPSC Prelims 1998 • Science and Technology

Correct Answer: Option (C) — Both of them give colour with iodine

Concept & Option Breakdown

Standard Reference Verified
  • Statement (a) is correct: Both starch and cellulose are natural biopolymers synthesized by plants.
  • Statement (b) is correct: Both are high-molecular-weight polysaccharides made of long chains of repeating units.
  • Statement (c) is incorrect: Starch forms a helical structure that traps iodine (triiodide ions) to give a characteristic deep blue-black color. Cellulose possesses a straight, uncoiled β-(1,4) glucan chain stabilized by hydrogen bonds and does not form this helical complex, thus giving no color with iodine solution.
  • Statement (d) is correct: Both are glucose polymers (starch contains α-D-glucose, whereas cellulose contains β-D-glucose).
Elimination Heuristic & Exam Approach

The iodine test is specific to the helical amylose in starch; cellulose's linear beta-linkages do not form a complex with iodine.

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Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 1998 (Q401)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Health & Medicine
Official Answer KeyOption (C) — Both of them give colour with iodine

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Assertion (A): Cellulose is used in making shatter-proof glass. Reason (R): Polysaccharides are not soluble in water. Codes:

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Frequently Asked Questions — UPSC Prelims 1998 Q401

What is the official answer for UPSC Prelims 1998 GS Paper I Question 401 (Science and Technology)?

The official UPSC answer key for this 1998 Science and Technology (Health & Medicine) question is Option (C): "Both of them give colour with iodine". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 1998 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Health & Medicine". You can explore all repeated questions from Health & Medicine in Acme AI's 3D Prelims PYQ Realm or practice 50 full-length and sectional tests in the APT Prelims Test Series.

How can I solve this Health & Medicine UPSC Prelims question using option elimination?

The iodine test is specific to the helical amylose in starch; cellulose's linear betalinkages do not form a complex with iodine.

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