Question

What is the difference between an antigen and a pathogen?

Answer 1

Hint: Both the terms come in relation to each other. The first term is in reference to the generation of the immune response by producing proteins while the second term is related to the cause of disease in the host body.

Complete answer
The difference between an antigen and a pathogen are as follows:

Antigen	Pathogen
It is simply a molecule.	It is an infection-causing agent.
It is found on the surface of the pathogens.	They are responsible for the causing of diseases.
They can be originated from both biological or non-biological sources.	They generally originated from biological sources that include microorganisms like fungi, and bacteria or even non-biological sources like viruses, or prions.
They are composed of lipids, polysaccharides, proteins, etc.	They are the microorganisms that include viruses, bacteria, fungi, protozoa, etc.
They are helpful in generating immune responses to fight certain diseases by producing Y-shaped proteins called antibodies.	They have unique antigens for binding to the host body via receptors.
They are generally found on the microorganisms and are formed by other substances like pollens, chemicals, etc.	The immune system will sense danger when they bind to their antigen and produce antibodies thus killing them.

Additional information
-Antibodies help in controlling the infection of body tissues against various microorganisms. They are produced by the immune system as a large protein in order to stop the functioning of the pathogens. For this process, a unique antigen for that particular pathogen is required for which a particular antibody is formed.
-Each antigen results in the formation of a specific antibody both fit together due to the presence of the complementary reactive sites like a lock and the key. Both got attached to each other through chemical bonding which is quite poor and non-covalent in nature.

Note:
Pathogenicity of microorganisms is referred to as the disease-causing ability of microorganisms. The degree of disease caused in the host by the microorganisms is used to express their pathogenicity. This pathogenicity measure is termed virulence. The pathogens that are highly virulent will cause more diseases to the host body.