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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 watch

  • View Poll Results: Are you resitting this unit?
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    (Original post by Cyanohydrin)
    Is there a Q&A thread thing - I find that a pretty good way of revising bio...?
    There isn't, but this can become one (they usually do nearer the time of the exam)

    What is Saltatory Conduction? (4 marks)
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    Thanks for helping to answer my kinesis question!
    xxx

    Does anyone else feel depressed when they see other people talking about how they are doing a practise essay every day? I have done 1 practise essay, with no time limit, I only filled 3/4 of a side, with help from my friend and my teacher. Oh****.
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    Can anyone please explain DNA sequencing on Chapter 16.6 for me please? The book's not helping, especially the each test-tube having nucleotides with the same base?

    TIA.
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    (Original post by skygirl999)
    Hi guys, I am stuck now on an exam style question from the nelson thornes textbook and I was wondering if anyone could help me out? It is page 210, question 3C? (It is a question from the homeostasis section based on the control of blood glucose?)
    Adrenaline is released as it is stimulated by stress/exercise, so it binds to the receptors and activates glycogenolysis, thus increasing the amount of glucose available for respiration. The glucose is used up by the muscles for contraction (and I guess you could mention the use of ATP in regards to the sarcoplasmic reticulum?), which lowers the glucose concentration in the blood. This is detected by the alpha cells on the islets of Langerhans, and so glucagon is released, causing further glycogenolysis.

    We went through this question in class. It is gross. D:
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    (Original post by Tericon)
    There isn't, but this can become one (they usually do nearer the time of the exam)

    What is Saltatory Conduction? (4 marks)
    awesome!

    Saltatory conduction is the propogation of action potentials along myelinated neurones. Myelinated neurones possess mylein sheafs - these are composed of schwaan cells wrapped around the axon that provide protection and electrical insulation for the axon. Nodes of ranvier are the gaps between the myelin sheafs. Action potentials only occur at the nodes of ranvier. The nodes of ranvier are depolarised by the postive sodium ions entering the node of ranvier during the action potential - this depolarisation passes down the node of ranvier by diffusion - causing the sodium ion channels to open as a result of depolarisation. When the action potential reaches the myelin sheaf it passes as a wave to the next node of ranvier - although it isn't as positive at the next node of ranvier it is positive enough to cause an action potential.

    I think that's correct??!

    Explain the process of muscle contraction with regards the myosin head and the actin (5 marks)
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    (Original post by appleschnapps)
    Adrenaline is released as it is stimulated by stress/exercise, so it binds to the receptors and activates glycogenolysis, thus increasing the amount of glucose available for respiration. The glucose is used up by the muscles for contraction (and I guess you could mention the use of ATP in regards to the sarcoplasmic reticulum?), which lowers the glucose concentration in the blood. This is detected by the alpha cells on the islets of Langerhans, and so glucagon is released, causing further glycogenolysis.

    We went through this question in class. It is gross. D:
    Ahhh I see, thank you I was unsure how much I would need to refer to the diagrams in that question. I think in the exam I would just write the answer and then try and write 'such as in figure 3/2' wherever it might be vaguely relevant!
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    (Original post by Jing_jing)
    Transcription factors control transcription. They bind to the promoter region which is upstream of the gene to be transcribed and this enables the mRNA polymerase to attach to the start of the gene. If an inhibitor molecule blocks the DNA binding site on the transcription factor it can no longer bind to the promoter region preventing transcription as the mRNA doesn't attach to the gene to be transcribed.

    In the case of oestrogen, the transcription factor and inhibitor molecule form a complex so the normally the inhibitor molecule is blocking the DNA binding site on the transcription factor preventing transcription. However, when oestrogen enters the cytoplasm (it's small and lipid soluble so it can diffuse easily through the phospholipid bilayer), it binds to a site on a receptor molecule of the transcription factor causing a conformational shape change and this releases the inhibitor molecule. This means that the DNA binding site of the transcription factor is no longer blocked, it can bind to the promotor region, causes transcription to start and hence polypeptide synthesis can take place.
    Do we have to know what specific polypeptides the oestrogen is transcribing?
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    (Original post by Cyanohydrin)
    awesome!

    Saltatory conduction is the propogation of action potentials along myelinated neurones. Myelinated neurones possess mylein sheafs - these are composed of schwaan cells wrapped around the axon that provide protection and electrical insulation for the axon. Nodes of ranvier are the gaps between the myelin sheafs. Action potentials only occur at the nodes of ranvier. The nodes of ranvier are depolarised by the postive sodium ions entering the node of ranvier during the action potential - this depolarisation passes down the node of ranvier by diffusion - causing the sodium ion channels to open as a result of depolarisation. When the action potential reaches the myelin sheaf it passes as a wave to the next node of ranvier - although it isn't as positive at the next node of ranvier it is positive enough to cause an action potential.

    I think that's correct??!
    Myelin sheaths not sheafs
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    (Original post by skygirl999)
    Myelin sheaths not sheafs.
    :yy:
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    Does anyone have any ideas on "The importance of water in biology"?
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    (Original post by Tericon)
    Yes, not much HSW at all for once! There's always one big HSW question in this unit, according to my biology teacher, question 10, the one before the essay.
    wow thats fortunate i wish i did that exam got a B in jan2011 but couldnt help thinking that i cud have got an A if i resitted
    i think theres more than one question
    like in june10 the question9 mayb 8 and 7 are mostly hsw questions
    i hate hsw questions:mad: hope theres isnt alot of them in the bio5 exam but i knw there wil be one
    wish the essay question isnt too hard
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    (Original post by snowgirl61862)
    Thanks for helping to answer my kinesis question!
    xxx

    Does anyone else feel depressed when they see other people talking about how they are doing a practise essay every day? I have done 1 practise essay, with no time limit, I only filled 3/4 of a side, with help from my friend and my teacher. Oh****.
    Lmfao I told myself I'd do a practice essay everyday of study leave until the exam. Study leave started on like the 3rd. Its now the 19th and I've done one :ahee:
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    (Original post by Cyanohydrin)
    Do we have to know what specific polypeptides the oestrogen is transcribing?
    I don't think so, just that it can be linked to breast cancer and therefore drugs which inhibit oestrogen can be used to treat breast cancer when caused by excessive amounts of oestrogen.
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    (Original post by NRican)
    Can anyone please explain DNA sequencing on Chapter 16.6 for me please? The book's not helping, especially the each test-tube having nucleotides with the same base?

    TIA.
    DNA sequencing is fun! (Disclaimer: it is not fun.) It is, however, fairly straight forward once you get it.

    DNA sample: it's a single strand so complementary base pairing will occur.
    DNA polymerase: joins the DNA nucleotides together.
    DNA primer: this is normally radioactively labelled, but it's also possible for the terminator nucleotides to be labelled instead. To detect the radioactive probe, put it on x-ray/photographic film and it will expose it. Can also be fluorescently labelled, in which case you put it under UV light so it'll fluoresce.
    Free nucleotides: When we were taught it, the normal nucleotides are all mixed into all the test tubes, it's only the
    Terminator nucleotides: that are separated out into different text tubes. When a terminator nucleotide is reached, no more bases can be added after it.

    They will then produce complementary strands of DNA to to the sample strand, and because whether it is a regular or normal nucleotide is random the strands produced are different lengths.

    e.g. For the complementary strand AATGCTAGC (based on the template strand TTACGATCG), in the A test tube, the following strands could be produced: A, AA, AATGCTA or AATGCTAGC. The same idea would follow for the T, C and G test tubes. The different length fragments of DNA are then placed onto an agar gel for electrophoresis.



    A voltage is passed through, and so they move towards the positively charged anode. Because they're of different lengths, they meet different levels of resistance and so don't all travel the same distance.



    Because there is a terminator nucleotide for each organic base, we can assume that every possible base sequence has been produced, and from that can work out the order of bases, as the shortest strands (e.g. A, AA, AAT) will be furthest away from the starting point, so we can number them from furthest away to closest to work out the order of bases.

    ... I kind of went a bit OTT there.
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    (Original post by laura123)
    Does anyone have any ideas on "The importance of water in biology"?
    - Formed in respiration as the terminal electron acceptor oxygen accepts a proton and an electron

    - Reactant in photosynthesis

    - Explain the importance of photosynthesis and respiration and some uses of ATP (because of the respiration) and how photosynthesis provides the glucose for respiration

    - Hydrolysis reactions - amino acids, carbohydrates

    - Osmosis and how water enters cells (lipid bilayer, effect of water upon cells etc)

    - Passage of water through a plant
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    (Original post by Cyanohydrin)
    - Formed in respiration as the terminal electron acceptor oxygen accepts a proton and an electron

    - Reactant in photosynthesis

    - Explain the importance of photosynthesis and respiration and some uses of ATP (because of the respiration) and how photosynthesis provides the glucose for respiration

    - Hydrolysis reactions - amino acids, carbohydrates

    - Osmosis and how water enters cells (lipid bilayer, effect of water upon cells etc)

    - Passage of water through a plant
    You could also fit something in there about how blood glucose concentration affects water potentials and the importance of BGC regulation in regards to brain cells losing water.
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    This is fairly similar but a bit harder I think:

    "The process of osmosis and it's importance to living organisms"

    This what I have so far:
    . Description of osmosis

    . Uptake of water into root cells, symplastic pathway through cytoplams by osmosis, uptake into xylem via active transport of ions into the xylem vessel

    . Keeping palisade cells turgid to provide max SA for sunlight

    .Treatment of diarrhoea e.g. from cholera: ORS - glucose and Na+ absorbed into epithelium via co-transport, lowers WP of epithelial cells - water flows by osmosis into epithelial cells - rehydrating

    . Uptake of excess water in large intestine - form solid faeces

    . capillaries - uptake of tissue fluid at venous end of capillary bed after exchange of substances between tissue fluid and cells

    . Insects at rest - tracheoles fill with water reducing rate of gas exchange. During flight/when active due to lactic acid production water is taken up by muscles by osmosis - increasing rate of gas exchange




    Thats basically most of what I could think of but it's difficult to link them together and I don't think thats enough for a full 3/4 page essay
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    guys any predictions on what the essay questions cud be
    my bio teacher sed that genetics is a hot topic atm so cud be an essay question
    but i hope that isnt true
    im hoping it isnt an essay that involves alot from AS
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    Could somebody just check that this is how you would describe transcription and translation? thanks

    Transcription
    1. Start of each gene is marked by a promotor region
    2. The section of the DNA that is to be transcribed is unwinded; hence exposing the DNA bases (unpaired)
    3. The mRNA nucleotides pair with the exposed bases via complementary base pairing
    4. RNA polymerase moves along one of the DNA strands forming an RNA sugar phosphate backbone - hence joining together the individual mRNA nucleotides forming pre-mRNA
    5. The DNA strand rejoins behind the RNA polymerase after transcription
    6. RNA polymerase reaches the stop codons and transcription stops

    Translation
    1. A ribosome (composed of mainly rRNA and proteins) attaches to the mRNA strand in the cytoplasm at the initiation codon (AUG)
    2. A tRNA molecule with a complimentary anticodon to AUG (UAC) diffuses to the ribosome and attaches to the first mRNA codon by complimentary base pairing - the tRNa moleucle carries the relevant amino acid - in the case AUG the amino acid is methionine
    3. The next tRNA molecule attaches to the next codon in the same way
    4. A peptide bond forms between the first amino acid and the second amino acid the bond between the first amino acid and the tRNA molcule is cut
    5. The ribosome moves along one codon - allowing another tRNA to bond via complementary base pairing
    6. Step 4 occurs again
    7. Gradually a polypeptide chain of amino acids is built up by steps 4 and 5
    8. Translation stops when the ribosome reaches a stop codon - at this point the protein is released
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    (Original post by hahaff)
    guys any predictions on what the essay questions cud be
    my bio teacher sed that genetics is a hot topic atm so cud be an essay question
    but i hope that isnt true
    im hoping it isnt an essay that involves alot from AS
    it's a mystery?! I wouldn't bother predicting - just get comfortable with the overarching topics - like diffusion/respiration etc etc
 
 
 
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