What are antihistamines ?

Both antacids and antiallergic drugs are antihistamines but they cannot replace each other. Explain why?

Name any three antihistamine drugs?

Explain the following with suitable examples. Antihistamines

Assertion : Penicillin (G) is an antihistamine. Reason : Penicillin (G) is effective against gram positive as well as gram negative bacteria.

What are histones? What are their functions?

What is biogas? What are its components ? What is the calorific value of biogas?