How Excretory Products Are Used In Medical Diagnosis

Question 1

What substances does urine contain

Answer 1

-urea
-water
-mineral salts
-hormones (if they’re small enough to be filtered through glomerulus)
-toxins

Question 2

What is being tested for in the urine of a pregnant woman?
Where does it come from and how soon can it be detected after becoming pregnant

Answer 2

-hCG hormone
-it is released from the developing embryo as it implants in the wall of the uterus at the site of the developing placenta
-it is detected within hours of implantation (which occurs within a week of fertilisation)

Question 3

Explain what monoclonal antibodies are and how they’re created to be used in pregnancy tests

Answer 3

-antibodies that are all identical, made from cloned cells, that are specific to one type of antigen
-mouse is injected with hCG which is recognised as non self, correct B lymphocytes activated to make the hCG antibody, these are removed from the mouse and fused with a cancer cell, hybridoma will rapidly divide and clone itself, collect and purify the antibody to us in pr

Question 4

What is an immunoassay?

Answer 4

Using antigens and antibodies to determine the presence of a substance E.g a pregnancy test

Question 5

Explain how a pregnancy test stick works in detecting the hormone hCG

Answer 5

-hCG is the pregnancy hormone in urine which is small enough to be filtered out of the blood, and small enough to be carried up the test strip
-if present, hCG molecules in the woman’s urine are carried up the test stick and bind to mobile antibodies to form hCG antibody complex. The dye is attached to these antibodies
-in the first window/band there are immobilised monoclonal antibodies for hCG antibody complex. The hCG antibody complex binds to these to form a coloured line if the woman is pregnant
-in the second window there are immobilised monoclonal antibodies which bind to excess mobile antibodies to form a coloured line whether the woman is pregnant or not, acting as the control to show the test has worked

Question 6

Explain how urine is used to detect the use of anabolic steroids (process of gas chromatography)

Answer 6

-anabolic steroids are drugs that build up muscle tissue
-some athletes are banned from taking these steroids as it may give them an unfair competitive advantage over other athletes, and they have dangerous side effects such as liver damage
-athletes have their urine tested for steroids by a technique called gas chromatography/ mass spectrometry:

-urine sample is vaporised and passed through a column containing a polymer
-different substances move through the column at different speeds, so substances in the urine sample separate out
-once separated a mass spectrometer converts them into ions, then separates them depending on mass and charge
-the results are analysed by a computer and by comparing them with the results of known substances it’s possible to tell which substances were in the urine sample

Question 7

Explain how urine is used to detect recreational drugs

Answer 7

1) sometimes people have their urine tested to see if they’ve been using recreational drugs such as cannabis or cocaine, some employers can carry out drug tests on their employers
2) test strips contain antibodies that the drug being tested will bind to. A sample of urine is applied and if a certain amount of the drug is present a colour change will occur indicating a positive result
3) if the first test shows a positive result a sample of urine is usually sent for further testing to confirm which drugs have been used, the second test using gas chromatography/ mass spectrometry