Where does mechanical and chemical breakdown start in the digestive system?
a. stomach
b. liver
c. small intestines
d. mouth/teeth

The answer is D.

Both mechanical and chemical digestion of food begin in the mouth.

Mechanical digestion involves physically breaking down food into smaller pieces. This happens in the mouth as the food is chewed. Adult humans have 32 specialized teeth which can tear, grind and chew different kinds of food.

Chemical digestion also begins in the mouth. It involves breaking down food into simpler nutrients that can be used by the cells. In the mouth, food is mixed with saliva. Saliva contains an enzyme  called salivary amylase that begins the breakdown of carbohydrates. Salivary glands beneath and in back of the tongue secrete the saliva.

answers are:

lysogenic     viral dna merges with host cell dna

lysogenic     no symptoms

lytic               viral dna takes over

lysogenic     virus does not destroy host cell

lytic               virus destroys host cell

lytic               induces symptoms of viral infection

lysogenic       cell reproduces and spreads provirus

the tricuspid valve is present between right atrium and right ventricle