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Thread: Bio exam thoughts

  1. #76
    Junior Member aycaramba's Avatar
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    Re: Bio exam thoughts

    Quote Originally Posted by asfdfasdf View Post
    How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
    i just talked about the different stages of action potential like the resting membrane potential where the na+/k+ pump kept the membrane potential at -70mV (referring to the graph ofc), the depolarisation due to influx of na+ into axon through the na+ ion channel which rapidly increases when threshold has been reached etc etc. Dunno if it's enough for a 3 marker tho

    BTW guys for multis, what did rosalind franklin discover? i was switching between the double helix structure and other the phosphate one and ended up picking the phosphate option
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    Re: Bio exam thoughts

    Double-helix
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    Re: Bio exam thoughts

    This is more or less what i wrote:

    Beadle and Tatum experimented with Neurosporra crassa (bread mould). They caused mutations to occur in the bread mould by using x-rays. This mutation resulted in the gene to be unable to code for the production of an enzyme that catalyses the production of a specific amino acid. This amino acid allowed the bread mould to grow, without it it would be unable to do so. From this they subsequently proposed the "one gene-one protein" hypothesis (they assumed that an enzyme was a protein and that one protein consisted of one polypeptide chain). It was later understood that proteins are made of more than one polypeptide hence their theory was modified to become the 'one gene-one polypeptide' theory. This allowed for the development of BT (Bacillus thuringiene) cotton. BT cotton is a trangenic species (a organism that contains the genes of another species and is able to pass this gene to its offspring) that is produced by isolating and cutting the BT gene from bacteria using a restriction enzyme. Then inserting it into cotton plant embryos via a vector. This embryo is then germinated and grown under tissue culture, producing the transgenic species. BT is a gene that results in the production of a enzyme that catalyses the development of a natural pesticide. This pesticide causes pest that come close to the plant to die. BT cotton has been beneficial as it saves money for farmers and reduces the harmful impacts of un-natural pesticides on the environment. Hence Beadle and Tatum's work has been imperative in the development of BT cotton through the theory that one gene codes for the production of one polypeptide.
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    I love trials pikachu975's Avatar
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    Re: Bio exam thoughts

    Quote Originally Posted by Mathew587 View Post
    you reckon this will be fine?

    https://dc.edu.au/wp-content/uploads...s-analysis.png

    i pretty much drew this but zoomed out like that one hsc q where they had a diagram with the pith in the middle and xylem and phloem if you remember?
    Quote Originally Posted by aycaramba View Post
    idk man i just drew a circle that was bigger than the phloem and labelled the outer layer a lignified cell wall???/
    Most of my class just drew a circle for xylem separated by cambium and a smaller circle for phloem to contrast differences in size

    Quote Originally Posted by jjHasm View Post
    My structure for the beadle and tatum (which im assuming will give me a 6-8/8 when i planned it): One gene-one protein --> one gene-one polypeptide --> understanding of DNA nowadays coding for favourable characteristics --> understanding of transgeneic species (definition and example/explanation) and favourable characteristic via picking specific polypeptide to code for desired characteristic, and isolating that gene etc --> little sum up of the whole flow chart, saying that if it werent for B&T, transgenic species wouldnt be possible and all this tech stuff wouldnt happen --> value of judgement since it was an assess q.
    We had this question in our trial u needed a detailed explanation of Beadle and Tatum's experiment, their results i.e. hypotheses, how one gene codes for one polypeptide relates to phenotype, transgenic species, and how one gene is extracted to transfer into the species relates to Beadle and Tatum's work.

    Quote Originally Posted by asfdfasdf View Post
    How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
    Basically wrote action potential referring to resting membrane potential of -90 mV approx and sodium/potassium etc.

    Quote Originally Posted by anton93 View Post
    For xylem I just drew a circle kinda thing with lignin thickening and for phloem I drew a sieve tube, perforated sieve plate, and a companion cell. Not sure what they're expecting since you can find so many different images for the transverse section of xylem and phloem online. Also about the hexagonal thing, I doubt that would be something marks will be taken off/awarded for, there are microscope images of xylem with a kind of round structure. I'm guessing the main thing is to note that xylem is thickened by lignin while phloem aren't and that phloem are living, xylem are dead at maturity.

    For the question about marine fish and freshwater fish I had a similar question in my trial where I got full marks for writing (summarised)
    - freshwater fish excrete dilute urine (have large glomeruli to filter large fluid volume)
    - freshwater fish excrete nitrogenous waste in the form of ammonia (majority lost via gills due to close proximity with water, some ammonia is excreted in urine, salt concentration of urine is low due to active reabsorption)
    - marine fish excrete conc urine to conserve water (nitrog waste excreted as urea, higher conc of salts in urine due to active secretion)

    But in the HSC I basically just wrote the dilute urine vs concentrated urine thing and explained using some structures (ie large vs small glomeruli corresponds to volume of fluid filtered, and loop of Henle is long in marine fish counter-current multiplier system to increase reabsorption of water which makes urine very concentrated) but didn't mention ammonia vs urea. Could I still get 4 marks?
    Woah I doubt you need all the stuff about glomeruli etc. I think simply contrasing their urine, what each fish loses to their environment, what goes into their body and why, etc should be enough.

    Quote Originally Posted by aycaramba View Post
    i just talked about the different stages of action potential like the resting membrane potential where the na+/k+ pump kept the membrane potential at -70mV (referring to the graph ofc), the depolarisation due to influx of na+ into axon through the na+ ion channel which rapidly increases when threshold has been reached etc etc. Dunno if it's enough for a 3 marker tho

    BTW guys for multis, what did rosalind franklin discover? i was switching between the double helix structure and other the phosphate one and ended up picking the phosphate option
    Double helix
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    Re: Bio exam thoughts

    pikachu975 how was my response, what do you think it'll get out of 8?

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    Re: Bio exam thoughts

    Quote Originally Posted by sourish View Post
    pikachu975 how was my response, what do you think it'll get out of 8?
    Depends on the marking criteria but in my trial I lost a mark for including not much detail for their experiment so you might lose one mark, and not sure if the link to one gene one polypeptide and how it relates to transgenics is enough so possibly 6-7
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    Re: Bio exam thoughts

    In class we learnt that Franklin discovered both sugar phosphate and double helix?
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    Re: Bio exam thoughts

    Quote Originally Posted by budgetjackiechan View Post
    In class we learnt that Franklin discovered both sugar phosphate and double helix?
    I just thought of that X-ray photograph she took, photograph 51 or something, that showed the double-helix structure Watson/Crick used to come up with the model of DNA. I'm pretty sure sugar-phosphate was someone else. Either that or... I wasn't paying attention in class
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    Re: Bio exam thoughts

    Yeah I learnt that too!

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    Re: Bio exam thoughts

    Quote Originally Posted by budgetjackiechan View Post
    In class we learnt that Franklin discovered both sugar phosphate and double helix?
    A few questions had some ambiguity with it this year with the MCQ so we'll see
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    Re: Bio exam thoughts

    Quote Originally Posted by sgtgummybear View Post
    I just thought of that X-ray photograph she took, photograph 51 or something, that showed the double-helix structure Watson/Crick used to come up with the model of DNA. I'm pretty sure sugar-phosphate was someone else. Either that or... I wasn't paying attention in class
    my teacher's notes said that Franklin was the first to discover the double helical nature of DNA and also the fact that the sugar phosphate backbone is external to the DNA molecule itself. So i assumed that someone else discovered the actual backbone. Guess I lucked out then!

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    Junior Member aycaramba's Avatar
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    Re: Bio exam thoughts

    Quote Originally Posted by r3 View Post
    my teacher's notes said that Franklin was the first to discover the double helical nature of DNA and also the fact that the sugar phosphate backbone is external to the DNA molecule itself. So i assumed that someone else discovered the actual backbone. Guess I lucked out then!

    Sent from my SM-N9208 using Tapatalk
    damn got confused thought watson and crick came up with the double helix structure first and franklin contributed through her knowldge of the backbone :'( im losing all my marks on multis HAHAH
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    Re: Bio exam thoughts

    Quote Originally Posted by asfdfasdf View Post
    How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right

    You had to talk about action potential and the changes in sodium (NA+) and potassium (K+), because its refering to electrochemical changes, so in signal 1 the impluse generated wasn't enough to exceed the threshold potential, however with signal 2 it was, therefore this impulse leads to a change in the electrochemical composition in order to pass the generated impulse through the axon in the neurone.

    Hope this helps!

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    Junior Member Snowflek's Avatar
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    Re: Bio exam thoughts

    What do you guys think the cut off for band 6 will be?

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    Re: Bio exam thoughts

    Quote Originally Posted by Snowflek View Post
    What do you guys think the cut off for band 6 will be?
    86
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    Re: Bio exam thoughts

    Quote Originally Posted by asfdfasdf View Post
    How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
    spoke about resting membrane potential and how the neurone is polarised then how when a stimulus that is able to exceed the threshold de polarisation occurs as Na+ diffuses into the cell and K+ diffuses out via the Na+/K+ exchange pump etc etc. i wanted that question to somehow be like a 4 or 5 marker bc i couldve written quite abit on it
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    Re: Bio exam thoughts

    Quote Originally Posted by Snowflek View Post
    What do you guys think the cut off for band 6 will be?
    I'll say about 83-84
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    Re: Bio exam thoughts

    I know I messed up the 8 marker on Beadle and Tatum and the 7 marker about hearing technologies (communication option), as well as a few other questions that weren't worth as many marks. The rest of the exam was pretty alright, only slightly harder than trials.

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    Re: Bio exam thoughts

    Quote Originally Posted by Brownie2829 View Post
    I'll say about 83-84
    85?
    83 seems to low tbh
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    Re: Bio exam thoughts

    Quote Originally Posted by Mathew587 View Post
    85?
    83 seems to low tbh
    Yeah but the average is usually about 79 for band 6, and it always seems to be a couple marks lower than what people expect (most are saying about 85/86 for this years one). It's really a guess though

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