Q.33 Archaeal cell membranes contain lipids that are
(A) Ether linked
(B) Ester linked
(C) Branched alkyl chain
(D) Linear alkyl chain
Archaeal cell membranes feature unique ether-linked lipids, distinguishing them from bacterial and eukaryotic ester-linked lipids. The correct answer to the MCQ is (A) Ether linked.
Option Analysis
Archaeal lipids use ether bonds to connect isoprenoid chains to a glycerol-1-phosphate backbone, providing stability in extreme environments.
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(A) Ether linked: Correct. Archaea employ ether linkages (C-O-C bonds) instead of ester bonds, making membranes resistant to hydrolysis, heat, and acidity.
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(B) Ester linked: Incorrect. Ester linkages (C-O-CO-C) characterize bacterial and eukaryotic membranes with fatty acids, which are less stable than archaeal ethers.
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(C) Branched alkyl chain: Partially true but incomplete. Archaeal chains are branched isoprenoids (phytanyl units with methyl branches), yet the defining feature is the ether linkage, not chain structure alone.
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(D) Linear alkyl chain: Incorrect. Linear chains typify bacterial fatty acids; archaeal chains feature branched, saturated isoprenoids for rigidity and packing.
Archaeal cell membranes ether-linked lipids form the core distinction from bacteria, enabling extremophile survival. These lipids feature ether bonds and branched isoprenoid chains, contrasting ester-linked fatty acids in other domains.
Ether-Linked vs Ester-Linked Lipids
Ether linkages in archaeal cell membranes provide chemical stability against harsh conditions like high temperature and pH. Bacterial ester-linked lipids hydrolyze easily, limiting extremophile adaptation.
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Ether bonds resist hydrolysis and oxidation.
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Ester bonds suit mesophilic environments.
Branched Alkyl Chains Role
Archaeal lipids contain branched alkyl chains from isoprene units (C20 phytanyl or C40 biphytanyl), enhancing membrane rigidity. Linear alkyl chains in bacteria allow fluidity but less stability.
CSIR NET Relevance
This topic tests membrane biochemistry in exams like CSIR NET Life Sciences. Ether-linked lipids highlight archaeal uniqueness in molecular biology.
