General Science Questions

PTH - Parathyroid hormone which balances calcium levels if they are low.

Potentially hazardous foods are foods that might contain food poisoning bacteria and are capable of supporting growth of these bacteria or formation of toxins to levels that are unsafe for consumers, if the foods are not stored at correct temperatures. Toxins are poisonous chemicals produced by some types of bacteria.

The food can be left at room temperature until it reaches 60 deg C because food-poisoning bacteria will not multiply at 60 deg C or above. However, do not leave food cooling at room temperature unless you are sure that the temperature of the food is still at least above 60 C.

A microscope is an instrument that magnifies objects. Cells that were first observed by Robert Hooke in the year 1665 in the compound microscope.

Molten rock inside the earth is called Magma.

In transfusions of packed red blood cells, individuals with type O Rh D negative blood are often called universal donors. Those with type AB Rh D positive blood are called universal recipients.

The immune system of a person with AB blood will accept blood from all possible donors, whether they have O, A, B, or AB blood. Since both A and B antigens are present in a person with AB blood, the recipient won't reject the blood. The body identifies that blood as "self" rather than "foreign."