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A2 Biology OCR June 2015 Revision Thread

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Man i am sooo scared for f215...I need atleast a B but im not even ready :frown: Half the time i don't even know what the question is asking...
Original post by bakedbeans247
Man i am sooo scared for f215...I need atleast a B but im not even ready :frown: Half the time i don't even know what the question is asking...


Same and I'm focussing on f214 now so f215 is being completely neglected :/
Reply 1382
Avatar for gdw808
gdw808
Does anyone have a list of the predicted topics for this year? For both F214 and F215? I'm getting nervous!
Original post by Beni24
why does excess paracetamol in the blood lead to liver failure/kidney failure? :smile:


For the detoxification of drugs (recreational or non such as paracetamol) you need NAD in order to accept the hydrogens when ethanol is converted to ethanol then acetate (ethanoic acid). However, if there is too much NAD to detoxify drugs then less can be sent to respiration, especially for fats when they are broken down to fatty acids and glycerol. If there is no NAD then they will form back to lipids causing enlargement of the liver, called fatty living which can lead to cirrhosis
Original post by gdw808
Does anyone have a list of the predicted topics for this year? For both F214 and F215? I'm getting nervous!


I've been looking around for one for a while, but no luck. So please let me know if you find one.

But for f214, I just looked through the last 7/8 papers in a few mins, and I haven't seen much of or there hasn't been any detailed questions on: how ADH works, a QWC type q. about action potentials, a QWC type q. about the transmission across the synpase, Calvin cycle, cyclic/non-cyclic photo phosphorylation (only 1-3 marker questions), how the structure of mitochondria enables them to carry out their function pg86, how chloroplasts are adapted for their role pg60, the bit about cofactors on pg87, oxidation phosphorylation, link and krebs cycle, how insulin is secreted from the beta cells in terms of K+ and Ca2+ ions, q.s about pages 28-29, q.s about pages 50-51 esp. the bit about testing for anabolic steroids, pages 96-97 esp. that section about lipids and the B-oxidation pathway.

now that above is what ive seen that hasn't come up, though im probs wrong with some of them as i flicked through 7/8 papers in a few mins.

But there is this predictions list from last year for f215 (scroll down, 2nd to last page highlighted in blue):

https://www.dropbox.com/s/c846q4mj16g26ek/f215%20stretch%20and%20challenge%20ideas.docx?dl=0

So, i guess anything that didn't come from that list in last years paper could be used to predict what will come up this yr? Although most of them did come up. :/
(edited 8 years ago)
Outline the evidence for chemiosmosis. (6)
Hi can someone explain this to me...
"describe how urine samples can be used to test for pregnancy and detect misuse of anabolic steroids"
Thank you!!
What's the need for the syringe in a photosynothmeter?
Original post by chinapicke
For the detoxification of drugs (recreational or non such as paracetamol) you need NAD in order to accept the hydrogens when ethanol is converted to ethanol then acetate (ethanoic acid). However, if there is too much NAD to detoxify drugs then less can be sent to respiration, especially for fats when they are broken down to fatty acids and glycerol. If there is no NAD then they will form back to lipids causing enlargement of the liver, called fatty living which can lead to cirrhosis


Thank you! so basically the same as what happens to alcohol :smile:
What is the b oxidation pathway? :smile:
Original post by HeyThereHarry
Outline the evidence for chemiosmosis. (6)


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!
Original post by Beni24
What is the b oxidation pathway? :smile:


The breakdown of fatty acids! ATP is converted to amp and two phosphryl groups added to fatty acids. This then is converted to 2-carbon acety groups which then undergo beta oxidation to form entry molecule for kerbs (acetate):smile:
Reply 1392
Avatar for tewas
tewas
2
Original post by buxtonarmy
What's the need for the syringe in a photosynothmeter?


i think it's to reset the air bubble in the capillary tube?
Reply 1393
Avatar for Juda19
Juda19
I'm actually dreading F215, i haven't even started revision for it yet. it's going to be awful >.<
Anyone got any tips on the best way to revise? Thanks!
Original post by lyd.maddox
Hi can someone explain this to me...
"describe how urine samples can be used to test for pregnancy and detect misuse of anabolic steroids"
Thank you!!


For Pregnancy:
human embryo secrets hGC as soon as it is implanted on the uterine lining. Hormone can be detected in the mother’s urine soon after (couple of days) Pregnancy tests contain monoclonal antibodies which are tagged with a blue bead and bind ONLY to hCG.hCG-antibody complex moves along the strip until it sticks to a band of immobilised antibodies, so forms a blue line. One blue line is control, so two blue lines means pregnancy

For Anabolic Steroids:
Process of Gas chromatography. Sample is vaporised in the presence of a gaseous solvent. Passed down a long tube lined with an absorbing agent.Each substance dissolves differently in the gas and stays there for a time known as the "retention time" Eventually substance leaves the gas and is absorbed by the lining. Analysis of results to make a chromatogram. Use a standard to identify drugs in urine.
Reply 1395
Avatar for GXO
GXO
2
Original post by buxtonarmy
What's the need for the syringe in a photosynothmeter?


to set the fluid in the manometer to a known level
Original post by domcandrews
For Pregnancy:
human embryo secrets hGC as soon as it is implanted on the uterine lining. Hormone can be detected in the mother’s urine soon after (couple of days) Pregnancy tests contain monoclonal antibodies which are tagged with a blue bead and bind ONLY to hCG.hCG-antibody complex moves along the strip until it sticks to a band of immobilised antibodies, so forms a blue line. One blue line is control, so two blue lines means pregnancy

For Anabolic Steroids:
Process of Gas chromatography. Sample is vaporised in the presence of a gaseous solvent. Passed down a long tube lined with an absorbing agent.Each substance dissolves differently in the gas and stays there for a time known as the "retention time" Eventually substance leaves the gas and is absorbed by the lining. Analysis of results to make a chromatogram. Use a standard to identify drugs in urine.


Thanks :smile:
Reply 1397
Avatar for tewas
tewas
2
Original post by GXO
to set the fluid in the manometer to a known level


is that not for respirometers?
What are the differences between the 3 types of epistasis. I know the ratios but don't understand their meanings.
recessive epistasis
dominant epistasis
complementary action
Original post by lyd.maddox
Hi can someone explain this to me...
"describe how urine samples can be used to test for pregnancy and detect misuse of anabolic steroids"
Thank you!!


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! :smile:

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