The immune system protects against foreign substances and even some cancers. explain how the
immune system functions. in your answer, be sure to:
• identify one way the immune system fights pathogens
• identify the substance in a vaccine that stimulates the immune system
• describe the response of the immune system to the vaccine
• identify one disease that damages the immune system and state how it affects this system

The immune system fights pathogens with white blood cells. Vaccines contain a weak sample of the virus or pathogen that it is intended to vaccinate, so the immune system is stimulated to fight the virus or pathogen. The immune system responds to the vaccine by fighting against it, and therefore, is prepared to fight the same structure of the pathogen. A severe stage of HIV is AIDS. AIDS does severe damage to the immune system and weakens it. It destroys T-cells that are essential for the immune system and immune response to pathogens.

A decomposition reaction occurs when one reactant breaks down into two or more products. It can be represented by the general equation:

AB → A + B

In this equation, AB represents the reactant that begins the reaction, and A and B represent the products of the reaction. The arrow shows the direction in which the reaction occurs.

Q: What is the chemical equation for the decomposition of hydrogen peroxide (H2O2) to water(H2O) and oxygen (O2)?

A: The equation for this decomposition reaction is:

2 H2O2 → 2 H2O + O2