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VCAA Sample Exam (2017) Solutions
Aakaash14:
Hey I have just finished doing the MCQs, can you please explain the following questions from MCQ:
Q11
Q17
Q19
vox nihili:
--- Quote from: Aakaash14 on September 05, 2017, 01:06:10 pm ---Hey I have just finished doing the MCQs, can you please explain the following questions from MCQ:
Q11
Q17
Q19
--- End quote ---
Hey there :) doing this on the train so pull me up if I've said anything silly
Q11: the picture shows a mitochondrion. The correct answer is C, because NADH provides electrons and hydrogen ions (H+) to the electron transport chain, thus turning NADH into NAD+. This is called cycling because glycolysis will turn the NAD+ back into NADH.
Let me know if you'd like me to explain why the other alternatives are wrong
Q17: this was a challenging question. Lipid based hormones can go straight through the membrane. That is because the membrane is a lipid; therefore, they zip right through.
If they can go right through, it stands to reason that their receptors will be inside the cell.
These receptors bind to the lipid hormone. Once they have bound, the receptor and the hormone together move into the nucleus where they bind to DNA and alter the transcription of genes.
I was surprised by Q17. The knowledge required was surprisingly technical.
Q19: another technical question but absolutely fair game. Relenza is a dot point on the study design.
Flu virus gets into cells by sticking onto the surface. Once that happens, the cells then take the flu virus up by endocytosis.
The virus then replicates inside the cell, making 1000s of flu babies.
When these are ready to leave, they move out of the cell by exocytosis. The problem is, the same things that allow flu to stick to the cell to invade it, make all the flu babies get stuck to the cell from which they're coming. Therefore to infect another cell, they have to become unstuck.
An enzyme called neuraminidase achieves this by cutting the sticky bits off the cell, therefore allowing those viruses to go and infect other cells.
Relenza was developed by first solving the structure of neuraminidase. Then what we did is we had a look at what the active site of the enzyme looks like and designed a drug that could fit in there and block it.
chrissle:
How can PCR be the answer for the modern method of identifying the pathogen? This method simply amplifies the DNA. Wouldn't a better answer be gene probes or gene sequencing?
I don't actually know the answer because my school didn't teach it :|
vox nihili:
--- Quote from: chrissle on September 11, 2017, 09:17:46 am ---How can PCR be the answer for the modern method of identifying the pathogen? This method simply amplifies the DNA. Wouldn't a better answer be gene probes or gene sequencing?
I don't actually know the answer because my school didn't teach it :|
--- End quote ---
Hey there :)
I thought this was a hard question and was surprised it was asked. The only reason I knew the answer is because I study medicine at the moment and this is actually how it's done :)
PCR can be used to amplify specific sequences of DNA. We do this by using probes that are specific to that DNA. In that way, you can choose a sequence for a bacterium to amplify. You'd then use gel electrophoresis to visualise the stretch of DNA you amplified with PCR. If the pathogen is in the blood sample, then you'll see the band on electrophoresis (because the DNA has been amplified) if it's not, the gel will be clear.
chrissle:
Thanks! ;D So to summarise the process is:
1. gene probes in sample to identify a specific sequence of DNA
2. amplify that DNA using PCR
3. Run DNA through gel electrophoresis
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