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    (Original post by susan23)
    really? whats the success rate in her predictions coming up in the past?? Lol
    Shes been like 90% right most of the time, trust me shes legit, obviously revise everything but focus on these areas and get them down, u never know, u could be thanking me tomorow afternoon. but again, i MAY be wrong.
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    Can someone please explain muscle contraction to me? I don't get the sliding filament model. Particularly where it talks about the myosin head unattaching and then reattaching. I don't get how myosin bending increases overlap either.
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    (Original post by SR198198)
    Shes been like 90% right most of the time, trust me shes legit, obviously revise everything but focus on these areas and get them down, u never know, u could be thanking me tomorow afternoon. but again, i MAY be wrong.
    i have a feeling she may be right....we shall see tomorrow though thanks

    (Original post by Kidms001)
    Probably quit revision for the F1 tonight, go to sleep at 11-30, get up at 8-30, panic revision, head to the exam about 12-30
    Sounds like a good plan. I was going to do the same haha
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    what is the relevance of blebs forming during apoptosis?????????? or do they just form because the cytoskeleton braeks down by enzymes?
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    (Original post by SR198198)
    Shes been like 90% right most of the time, trust me shes legit, obviously revise everything but focus on these areas and get them down, u never know, u could be thanking me tomorow afternoon. but again, i MAY be wrong.
    give me the list pleaseee!!
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    (Original post by Killmepls)
    Can someone please explain muscle contraction to me? I don't get the sliding filament model. Particularly where it talks about the myosin head unattaching and then reattaching. I don't get how myosin bending increases overlap either.
    Myosin and actin are the two proteins that actually cause the muscle to contract. Myosin is like a claw that is attached to the actin, which is like a ladder with rungs. The myosin goes through a cycle to produce contraction:

    1. ATP binds to the myosin head, causing it to release the actin filament
    2. The ATP is hydrolysed into ADP and phosphate, the energy is used to “cock” the myosin into a high energy state
    3. The phosphate is released, and the myosin is forced back into the actin. Now, the myosin is one “rung” forward
    4. The ADP is then ejected, step 1 is re-initiated

    You could think of it as the myosin crawls up the actin. Its like a ratchet mechanism

    But, there are two more proteins which control the muscular contraction. These are tropomyosin and troponin. The tropomyosin is wrapped around the actin and it is held into place by troponin. (you could think of the troponin as nails). When the troponin and tropomyosin are in place, they block the binding sites for myosin. So, myosin cant "crawl" up the actin and there is no contraction.

    However, in the presence of calcium, calcium will bind to troponin and cause it to move the tropomyosin out of the way. So, the binding sites are exposed and myosin can "crawl" up the actin
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    (Original post by Killmepls)
    Can someone please explain muscle contraction to me? I don't get the sliding filament model. Particularly where it talks about the myosin head unattaching and then reattaching. I don't get how myosin bending increases overlap either.


    How I understand it:

    • The myosin heads try to attach to form cross-bridges on the actin filament, however, it is normally covered by troponin and tropomyosin.
    • Calcium ions non-competitively inhibit the troponin so that it changes shape, moving troponin and tropomyosin away from the binding area, allowing cross-bridges to form.
    • The heads bend, moving the actin along (contraction). This is now a stable form.
    • ATP is required to break the cross-bridge and move the myosin head back to it's orginal position, so it is hydrolysed into ADP + P.
    • Repeat if there are still Calcium ions around.


    Hope that helps

    Imagine the myosin head like your arm. It pulls by making a "windscreen wiper" motion. At least that's how I imagine it :rofl:
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    (Original post by Killmepls)
    Can someone please explain muscle contraction to me? I don't get the sliding filament model. Particularly where it talks about the myosin head unattaching and then reattaching. I don't get how myosin bending increases overlap either.
    its part of the POWER STROKE :

    Myosin head group attaches to the thin actin filament, forms a cross bridge

    head group bends causing thin filament to be pulled along, which overlaps the thick filament. it hyrdrolyses atp so adp +pi are released. (this is where the overlapping comes in)

    the cross bridge breaks as an atp attaches to the mysosin head. this gives it energy to break

    head group moves back and re attaches as a result.

    the reattaching and attaching is going back then forth so it causes it to pull along the thin actin filament, therefore contraction happens because "movement of actin filaments=muscle contraction" contraction cycle continues if atp is available and ca2+ level in sarcoplasm is high. (of course there must be calcium as this is what moves the troponin+tropomyosin off the actin raection site for myosin to attach)


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    (Original post by rebeccalouise_92)
    what is the relevance of blebs forming during apoptosis?????????? or do they just form because the cytoskeleton braeks down by enzymes?
    "In cell biology, a bleb is an irregular bulge in the plasma membrane of a cell caused by localized decoupling of the cytoskeleton from the plasma membrane" - Wikipedia

    So you are right, although i dont think we need to know blebbing in such detail
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    (Original post by Kidms001)
    Ahh.. I follow you :facepalm:


    This exam is sending me loopy! :rave:
    Ahaha, don't worry me too! I keep hearing noises in my house even though I'm the only one here, and I keep deeling like someone's staring at me from the garden... but there's no one there :erm:
    Ok I didn't realise how weird that sounds until I wrote it down... now I sound like a psycho

    On the plus side, I just found this :parrot: and it's now my favourite thing ever.

    (Original post by Kaph)
    Ahhh awesome What course you applying for?

    I think my F214 was a minor fluke aha, seeing as I got a U in chem :eek:.
    Zoology you?
    Haha no I'm sure it wasn't! But yeah, obviously if you don't get a U at some point in your life, you're just not cool
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    do we need to know about bacterial conjugation?
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    (Original post by snkishy)
    do we need to know about bacterial conjugation?
    Yepp
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    (Original post by snkishy)
    do we need to know about bacterial conjugation?
    you need to know the advantage of it to microorganisms.. eg sharing antibiotic resistance (i think)
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    someone tell me what we need to know about dopamine and drd4 receptors please?
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    (Original post by susan23)
    What time are you guys going to sleep today?
    i think im gonna try and sleep earlyish like 11 then wake up earlyish to go over the suggested topics that could come up how about you?
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    (Original post by thecookiem0nster)
    Here are my predictions on what may come up, based on what has been covered in january and june

    Define genetic code
    Cyclic AMP and how it activates proteins
    Apoptosis
    Meiosis + Crossing over, possibly a question combined with genetic linkage
    Some genetic definitions
    How variation arises from meiosis and fertilisation
    An epistatic punnett square question, maybe combined with chi-squared or Hardy-weinberg
    Continuous/Discontinuous variation
    Natural selection and isolation mechanisms, maybe with genetic drift
    Define biological/phylogenetic species concepts
    Bread wheat and artificial selection or golden rice
    Describe how tissue culture is carried out, along with advantages/disadvantages of cloning
    Why are microorganisms used in biotechnological processes
    How to immobilise enzymes
    Outline how genetic sequencing of an organism is carried out
    Define recombinant DNA
    How DNA probes can be used in genetic screening
    Something to do with plasmids/vectors and how bacteria can take up DNA
    Xenotransplantation
    Define Gene therapy
    Ethics of Genetic manipulation
    Succession and climax communities. possible example question
    Predator-prey relationship
    Galagapos Islands
    The nervous system and brain stucture/function possible table comparison question?
    The sliding filament model and how ATP supply to muscles is maintained
    Definitions of Escape reflexes/Taxes/Kineses
    Advantages of innate/learned behaviour, possible long comparison question?
    a bit too much for one exam.. don't you think?
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    (Original post by sillysal)
    someone tell me what we need to know about dopamine and drd4 receptors please?
    Studies have shown different alleles of the DRD4 gene to be linked to ADHD. The condition is not fully genetic, or environmental.

    Individuals with ADHD can show abnormal behavior, or excessive gambling. Therefore, genotype affects human behaviour
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    (Original post by greenford)
    a bit too much for one exam.. don't you think?
    Yeah lol... I said what "may" come up. Its what I think could come up, but not all of it will
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    (Original post by thecookiem0nster)
    Studies have shown different alleles of the DRD4 gene to be linked to ADHD. The condition is not fully genetic, or environmental.

    Individuals with ADHD can show abnormal behavior, or excessive gambling. Therefore, genotype affects human behaviour
    thankyou!
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    Could I have some sympatric speciation examples and biotic and abiotic environmental pressures please?

    Thanks in advance
 
 
 
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