Given below are two statements:
• [Statement (I):] The lipids found in the inner (cell) membrane of bacteria are phospholipids.
• [Statement (II):] The lipids in the outer membrane of Gram negative bacteria contain both phospholipids and lipopolysaccharides.
In light of the above statements, choose the most appropriate answer from the options given below.
Given below are two statements:
• [Statement (I):] The lipids found in the inner (cell) membrane of bacteria are phospholipids.
• [Statement (II):] The lipids in the outer membrane of Gram negative bacteria contain both phospholipids and lipopolysaccharides.
In light of the above statements, choose the most appropriate answer from the options given below.
Show Hint
It is also the endotoxin responsible for triggering severe immune responses (toxic shock) in animals.
- Both Statement (I) and Statement (II) are correct.
- Both Statement (I) and Statement (II) are incorrect.
- Statement (I) is correct but Statement (II) is incorrect.
- Statement (I) is incorrect but Statement (II) is correct.
The Correct Option is A
Solution and Explanation
Bacterial cell membranes are lipid bilayers that provide structural integrity and regulate the transport of substances into and out of the cell.
Gram-negative bacteria have a unique envelope structure consisting of an inner cytoplasmic membrane and an outer membrane.
Step 3: Detailed Explanation:
Let us evaluate both statements:
- Statement (I) is correct: The inner (cytoplasmic) membrane of both Gram-positive and Gram-negative bacteria is a classic symmetric bilayer.
It is composed primarily of amphipathic phospholipids, such as phosphatidylethanolamine and phosphatidylglycerol, which form a selective barrier.
- Statement (II) is correct: The outer membrane of Gram-negative bacteria is an asymmetric lipid bilayer.
The inner leaflet of this outer membrane contains standard phospholipids.
However, the outer leaflet is composed mainly of glycolipids, specifically lipopolysaccharides (LPS).
LPS consists of Lipid A (an endotoxin), a core polysaccharide, and an O-antigen chain.
Therefore, the outer membrane contains both phospholipids and lipopolysaccharides.
Thus, both statements are correct.
Step 4: Final Answer:
Both Statement (I) and Statement (II) are correct, matching Option (A).
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