A2 Biology OCR June 2015 Revision Thread

Researchers isolated mitochondria - placed them in a solution with a very low w.p. The outer membrane ruptured, releasing the contents of the intermembrane space. Further treatment of mitoblasts led to exposure of matrix. Allowed researchers to identify enzymes in the mitochondria, and to work out that the link reaction and Krebs cycle occurred in the matrix, and the enzymes for the E.T.C were embedded in the mitochondrial membrane. Electron transfer in mitoblasts did not produce ATP - conclusion that the intermembrane space was also involved. ATP not made if the mushroom-shaped parts of the stalked particles were removed from the inner m/r of the intact mitochondria. ATP not made in the presence of oligomycin (blocks the flow of protons through the ion channel part of ATP synthase). In the intact mitochondria: The p.d across the membrane was -200mV, being more negative on the matrix side than on the intermembrane space side and also pH of the intermembrane space was lower than that of the matrix.

Probably don't need to mention all of these but hopes this gives you an idea of what you would write!

Awesome! But watch out — to rupture the outer mitochondrial membrane you'd need to place them in a solution with a very high water potential, not low. That's one of the mistakes in the book

Anyone know where I can find last years unit 4 and 5 papers?

What is the difference between neurotransmitter and an impulse ?

Can someone pleeaaaase explain excretion in detail, I always get confused with whats in the filtrate and capillaries

Can someone pleeaaaase explain excretion in detail, I always get confused with whats in the filtrate and capillaries

Pregnancy:
During pregnancy the placenta produces the hormone human chorionic gonadotrophin (hCG). Some of it is lost to the urine and only pregnant women produce hCG, so a urine sample is used to test for pregnancy as hCG will only be present if the woman is pregnant. When a woman takes a pregnancy test, urine passes into the reaction zone of the test stick and some of the monoclonal antibodies there bind to hCG, others do not. These monoclonal antibodies recognise one specific feature of hCG and will only bind to that one; they have blue beads attached to them. All of the monoclonal antibodies pass down to the testing zone which contains polyclonal antibodies which are immobilised. These polyclonal antibodies can bind to numerous parts of hCG so are able to bind despite the fact that the monoclonal ones are attached. Since the polyclonal antibodies are immobilised on the strip, the hCG and thus the blue beads are fixed in this zone, causing it to turn blue. The monoclonal antibodies that didn't bind to hCG move along the strip to the control zone which also contains immobilised antibodies. The monoclonal antibodies bind to the control antibodies, which turns this zone blue as well since all the monoclonal antibodies have blue beads attached. Two blue lines indicates pregnancy.

Anabolic steroids:
The misuse of anabolic steroids can be tested for using gas chromatography. A sample of urine is vaporised in the presence of a gaseous solvent and is passed down a long tube lined by an absorption agent. Every substance will dissolve differently in the gas and each will remain in the gas for a unique retention time. Eventually, each substance will come out of the gas and be absorbed onto the lining of the tube by the absorption agent. This is then analysed to create a chromatogram. Chromatograms are also produced in this way of drug samples so that different drugs can be identified and quantified in the chromatogram of the urine sample.

Hope this helps!

Describe the role of glycolysis in cellular respiration. (6)

Could someone have a look at these notes, they were posted on another thread, very spec relevant, are they good enough to get an A/B? Or should I stick to textbook?

can anyone expalin the secretion of ADH please?