All of the following pertain to virus envelopes except they:

• A. may help the virus evade the host immune system
• B. are present in all viruses
• C. contain viral glycoproteins important for attachment
• D. are composed primarily of lipids derived from the host cell membrane

Answer: (B)

Verified step by step guidance

1. Step 1: Understand what a virus envelope is. A virus envelope is a lipid bilayer membrane that surrounds some viruses, derived from the host cell membrane during viral budding.
2. Step 2: Recognize the functions of the virus envelope. It often contains viral glycoproteins that are crucial for attachment to host cells and can help the virus evade the host immune system by mimicking host molecules.
3. Step 3: Identify that not all viruses have envelopes. Some viruses are non-enveloped (naked viruses) and lack this lipid membrane, which means envelopes are not present in all viruses.
4. Step 4: Analyze each statement in the problem: (a) envelopes may help evade the immune system - true; (b) envelopes are present in all viruses - false; (c) envelopes contain viral glycoproteins important for attachment - true; (d) envelopes are composed primarily of lipids derived from the host cell membrane - true.
5. Step 5: Conclude that the statement 'are present in all viruses' is the exception because envelopes are only found in some viruses, not all.