How does an antihistamine reduce allergy symptoms? How does an antihistamine reduce allergy symptoms? a. An antihistamine binds
pollen antigens, preventing them from provoking an allergic reaction. b. An antihistamine blocks receptors for inflammatory chemicals released from granules within mast cells. c. An antihistamine kills mast cells, blocking an allergic reaction.
b. An antihistamine blocks receptors for inflammatory chemicals released from granules within mast cells.
Explanation:
The mast cells situated at the body surfaces are responsible for alerting the immune system when a local infection is detected. This induces the secretion of inflammatory chemicals from granules within the mast cells once activated. Histamine is released which causes the blood vessels to expand and the skin to swell, thereby protecting the body. This leads to the production of symptoms like sneezing and rashes.
This allergic response to the perceived antigen is initiated as a result of the degranulation of the mast cell.
An antihistamine helps in stopping the histamine from affecting the cells in the body by blocking the receptors for the inflammatory chemicals released from granules within mast cells
Key Points Diploid cells are cells with two sets of chromosomes. They have twice the chromosome number of haploid cells. Somatic cells (body cells excluding sex cells) are examples of diploid cells. The diploid chromosome number is the number of chromosomes within a cell's nucleus.
<u>The inducer in the lac operon is allolactose. Allolactose is the inducer of lac operon since it turns on, or induces the expression of the lac genes. </u>
In the presence of lactose in the medium, some amount of lactose will be converted to allolactose by the enzymes β-galactosidase present in the cell.
Consequently Allolactose binds to the repressor molecule, hence reducing the repressor's affinity for the operator site.