GCE A/L Biology case studies
GCE A/L Biology · Put your knowledge to work in context.
The GCE Advanced Level Biology examination is the subject paper taken by students in Sri Lanka's Advanced Level (A/L) programme, typically in the science stream, and it is used for university admission and for many science-related training and employment routes. It rewards a working command of biology as a connected discipline rather than a list of facts: cell biology and basic biochemistry underpin genetics and molecular biology, which in turn feed into plant and animal physiology, microbiology and immunity, ecology and evolution, and applied topics such as biotechnology. The GCE A/L Biology case studies are 5 cases and about 4,093 words.
1Catalase Kinetics: Reading a Plateau and Diagnosing an Inhibitor
A student homogenised 20 g of potato tissue in cold buffer and used the supernatant, after centrifugation, as a source of catalase. She measured the volume of oxygen released in one minute when 2 cm3 of extract was added to 20 cm3 of hydrogen peroxide at pH 7.0 and 25 °C.
848 words, about 4 min2Mitotic Index and a Colchicine Block: Proportion Is Not Rate
Students squashed the tips of onion roots (2n = 16) and counted 2000 cells in one slide: 1780 in interphase, 120 in prophase, 45 in metaphase, 25 in anaphase and 30 in telophase. A previous experiment using labelled thymidine had shown that the whole cell cycle in these roots takes 20 hours.
790 words, about 4 min3Cousins, a Carrier Test and a Residual Risk
Salma and Omar are first cousins. They are both unaffected but have a son with a rare autosomal recessive condition, confirmed by enzyme assay.
767 words, about 4 min4Mineral Deficiency Symptoms and a Potometer Reading
Tomato plants were grown for four weeks in aerated nutrient solutions: complete, minus magnesium, and minus nitrate. The complete plants were healthy.
841 words, about 4 min5Hyponatraemia at the End of an Ultramarathon
A 30-year-old runner completed a five-hour ultramarathon in 30 °C heat. Over the race she lost 4.0 L of sweat containing 40 mmol dm-3 sodium and drank 6.0 L of plain water.
847 words, about 4 min