Metabolic reactions create waste products which can become toxic if not removed. Removal of waste products is known as excretion
Key waste products in excretion
Carbon dioxide
Nitrogenous waste (e.g., urea)
Carbon dioxide is excreted from the lungs during exhalation
Urea is created from excess amino acids in the diet and is excreted through the kidneys
Types of nitrogenous waste produced by different animals
Mammals produce urea, fish produce ammonia, birds produce uric acid
Marginal utility
The additional utility (satisfaction) gained from the consumption of an additional product
Osmosis
The movement of water from an area of high concentration to an area of low concentration through a selectively permeable membrane
Diffusion
The movement of particles from an area of high concentration to an area of low concentration
Urine can be used for diagnosing various conditions such as diabetes, pregnancy, presence of anabolic steroids, and other drugs
Pregnancy tests use monoclonal antibodies to detect the human growth hormone produced by pregnant women
Monoclonal antibodies are single types of antibodies that can be isolated and cloned
Pregnancy test process
Urine sample absorbed by the absorbent end of the pregnancy test, mobile monoclonal antibodies in the test are complementary to the human growth hormone, if pregnant, the human growth hormone binds to the mobile monoclonal antibodies with a colored dye attached, as urine moves up the paper, the mobile antibodies move with it, at a certain position, there is a second immobilised monoclonal antibody
Pregnancy test
1. Human growth hormone in urine binds to mobile monoclonal antibodies with colored dye attached
2. Second immobilized monoclonal antibody at position C binds to first antibodies if present, creating a blue strip
3. Third immobilized antibody at position D binds to moving antibodies, creating a second blue line as a control strip
Two blue lines in a pregnancy test indicate pregnancy, one line indicates not pregnant
Anabolic steroids can be tested for in urine similar to pregnancy tests, along with other drugs
