Question

A host organism needs time, often days, to mount an immune response against a new antigen, but memory cells permit a rapid response to pathogens previously encountered. A vaccine to protect against a particular viral infection often consists of weakened or killed virus or isolated proteins from a viral protein coat. When injected into a person, the vaccine generally does not cause an infection and illness, but it effectively teaches the immune system what the viral particles look like, stimulating the production of memory cells. On subsequent infection, memory cells recognize and bind to the virus and trigger a rapid immune response. Some pathogens, including HIV, have developed mechanisms to evade the immune system, making it difficult or impossible to develop effective vaccines against them. Assume that a host's antibodies and T-cell receptors are available to bind to any structure that might appear on the surface of a pathogen and that, once bound, the pathogen is destroyed. What strategy could a pathogenic virus use to evade the immune system? Antibodies on the virus mutate often. The viral antigens are altered repeatedly. The virus can target, infect, and destroy immune system cells. Viral particles prevent immune cells from making antibodies. The viral particles do not encode proteins.

Answer 1

1. The viral antigens are altered repeatedly.

The virus can target, infect, and destroy immune system cells.

2.

Muscles cells store only enough ATP to complete a few contractions.After using up the readily available ATP,muscles cells can form additional ATP from:
1) Creatine phosphate- provides ATP for short term during muscle contractions.

2) Glycolysis- Provide enough ATP by using glucose molecule.

3) Cellular respiration-Provides ATP for a long interval.

3.  

1. The antigen-binding site is formed as a combination of variable domains from one heavy and one light chain.

2. The heavy and light chains are linked by noncovalent and disulfide bonds.

3. Both Fab and Fc fragments contain constant domains.