How can urine be used to detect pregnancy?

The hormone Human Chorionic Gonadotrophin (HCG) starts to be secreted six days after conception from a developing embryo. A pregnancy test stick has three bands. In the first are monoclonal antibodies which are specific to HCG and are associated with a pigment activating- enzyme. When placed in urine, the fluid moves up the test strip passing first band, allowing any HCG present to bind to these antibody-enzyme complexes. As the complexes (also bound to HCG) move up to the second band (the test zone), another enzyme will bind to each complex on one of HCG’s 5 binding sites forming a sandwich assay. The assay sticks to the test band allowing the enzyme molecule to activate the dye and a blue line is produced. If HGC isn’t present, an assay wont form and no dye will be released. Any unbound enzyme-complexes (bound to HCG) from the first strip will end up in the last band, the control, and should activate more dye. if not, the test was faulty. A positive test therefore should give two blue lines and a negative, none.

Answered by Aimee W. Biology tutor

3012 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

Describe the events of the cholinergic synapse


What are the enzymes involved at each stage during DNA replication?


What is a mutation and what are the consequences of one?


Explain how an electrochemical gradient is formed in the mitochondria, and how this gradient is used to synthesise ATP.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences