Question

1. why is yeast added to the mixture made for making cake? explain.

2. to prevent a disease caused by a certain microbe,doctor's inject the same microbes in a person's blood.how is ensured that this prevents the disease,instead of causing it?

Answer 1

Yeast is a leavening agent. In other words it may be called raising agent i.e it is used to raise the dough to make it light soft and porous. Yeast reproduces rapidly and produce carbon dioxide that fill dough which make it porous and increases its volume. This is actually called raising of dough. Yeast is available as a powdered form and adds flavour and aroma to the baked product

Prevention of many diseases caused by microorganisms is achieved by vaccines, that are injected in our body. These vaccines are actually dead, inactive or weakened microbes of the same disease. These organisms i.e virus or bacteria are made weak enough to cause the particular disease in a healthy person. But, they are capable of producing antibodies of that particular disease thus provide immunity and prevent, from the further invasion of same virus or bacteria.