Hey there! Sign in to join this conversationNew here? Join for free

Edexcel A2 Biology SNAB 6BI04 ~ 6BIO5 June 2016 Watch

Announcements
    Offline

    12
    ReputationRep:
    (Original post by alexfrances)
    For glycolysis you're producing two reduced NAD because there are two 3 carbon molecules.

    in my notes from class NAD gets reduced to produce NADH + H+ in the krebs cycle and in the CGP text book during oxidative phosphorylation reduced NAD releases 2 hydrogen atoms to produce two electrons.

    Not sure if this helped whatsoever cause i'm starting to confuse myself but if you look in the CGP textbook for the oxid. phos. you can see reduced NAD releases two hydrogen atoms
    ah yes I think you're right
    Cheers
    Offline

    6
    ReputationRep:
    (Original post by Sebmooc)
    Hi, 2 hydrogens reduce one NAD and 1 H20 molecule will be made from 1 NADH (as it releases to 2 H).

    Hope that helps.
    Ahh thank you!
    Offline

    6
    ReputationRep:
    Unit 5 questions are actually so hard :/
    Offline

    2
    ReputationRep:
    I had a question about redox reactions. In the book it says that reduction occurs when electrons or hydrogen atoms are added, or when oxygen is removed. Why does removing oxygen cause reduction?
    Offline

    1
    ReputationRep:
    (Original post by etherealinsanity)
    I had a question about redox reactions. In the book it says that reduction occurs when electrons or hydrogen atoms are added, or when oxygen is removed. Why does removing oxygen cause reduction?
    Oxidation is the loss of electrons OR adding oxygen so, reduction happens when oxygen is removed
    Offline

    2
    ReputationRep:
    (Original post by Jolalay)
    Oxidation is the loss of electrons OR adding oxygen so, reduction happens when oxygen is removed
    It says that in the book as well, but I get confused with oxygen and its role in redox reactions. I know that oxidation is the loss of electrons. But oxygen has electrons too so when oxygen is added, don't electrons get added too? So if those electrons are added, why is it still described as oxidation, which should be the loss of electrons?

    I know the book says oxidation occurs when oxygen is added and I accept that because I've seen it in other places as well. I just want to understand why adding oxygen is described as oxidation, and removing oxygen is described as reduction.

    I'm sorry if it's a really stupid question. I just can't get my head around it.
    Offline

    2
    ReputationRep:
    Also, for the structure of a mitochondrion, how should I draw the outer membrane? I've seen it drawn different ways on the internet. I've attached two images and I'm never sure which is the right drawing.
    Attached Images
     
    Offline

    1
    ReputationRep:
    (Original post by etherealinsanity)
    Also, for the structure of a mitochondrion, how should I draw the outer membrane? I've seen it drawn different ways on the internet. I've attached two images and I'm never sure which is the right drawing.
    First one - definitely .... there are only 2 membranes in the mitochondrion. Outer membrane is single membrane and inner membrane is the one that is folded into cristae. Have seen this commented in Examiner's report
    Offline

    2
    ReputationRep:
    (Original post by Moleyeyes)
    First one - definitely .... there are only 2 membranes in the mitochondrion. Outer membrane is single membrane and inner membrane is the one that is folded into cristae. Have seen this commented in Examiner's report
    Thank you!
    Offline

    2
    ReputationRep:
    (Original post by etherealinsanity)
    It says that in the book as well, but I get confused with oxygen and its role in redox reactions. I know that oxidation is the loss of electrons. But oxygen has electrons too so when oxygen is added, don't electrons get added too? So if those electrons are added, why is it still described as oxidation, which should be the loss of electrons?

    I know the book says oxidation occurs when oxygen is added and I accept that because I've seen it in other places as well. I just want to understand why adding oxygen is described as oxidation, and removing oxygen is described as reduction.

    I'm sorry if it's a really stupid question. I just can't get my head around it.
    Reduction and oxidation are defined in different ways. It can be in terms of oxygen, hydrogen and electron transfer.
    -When a compound gains oxygen it is oxidised, when it looses oxygen it is reduced
    -When a compound gains hydrogen it is reduced, when it looses hydrogen it is oxidised.
    -When a compound gains electrons it is reduced,when it looses electrons it is oxidised.
    When a compound gains oxygen, it is oxidised because it is referring to the first definition, (eventhough oxygen has electrons the overall oxidation state of the compound will become more positive as the whole compound will loose more electrons then it will gain). This is getting more into the chemistry side of things tho.
    Hope this helps

    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by _H_V)
    Reduction and oxidation are defined in different ways. It can be in terms of oxygen, hydrogen and electron transfer.
    -When a compound gains oxygen it is oxidised, when it looses oxygen it is reduced
    -When a compound gains hydrogen it is reduced, when it looses hydrogen it is oxidised.
    -When a compound gains electrons it is reduced,when it looses electrons it is oxidised.
    When a compound gains oxygen, it is oxidised because it is referring to the first definition, (eventhough oxygen has electrons the overall oxidation state of the compound will become more positive as the whole compound will loose more electrons then it will gain). This is getting more into the chemistry side of things tho.
    Hope this helps

    Posted from TSR Mobile
    Okay. Thank you.

    I did AS chemistry last year, but we always used the idea of loss or gain of electrons to define oxidation and reduction, so it confused me.
    Offline

    1
    ReputationRep:
    (Original post by Ladymusiclover)
    Do we need to learn about the enzymes involved in glycolysis? I know there's phosphofructokinase do we need to learn the others.
    We don't need to know about any specific enzymes apart from atpsynthase for respiration
    Offline

    2
    ReputationRep:
    https://www.tes.com/news/school-news...fair-advantage
    Offline

    0
    ReputationRep:
    Can someone send me a link to the pre release please ?
    Offline

    2
    ReputationRep:
    Grade boundaries are set depending on how everyone has done right? Judging by the number of those signatures seems like the majority of us found it challenging so hopefully even if Edexcel aren't cooperating now they'll be forced to acknowledge it once all the papers have been marked! Unless we have all been underestimating ourselves haha
    Offline

    1
    ReputationRep:
    I don't know about a rehash of another paper (I don't have time to go through it), but that image was NOT "clear". I've seen clearer mud. I know some people have argued that it had to be either Golgi or rER because it asked about protein synthesis, and that is true, but if you're provided with an image to identify, your answer should not have to depend on "detective work" (kind of pointless having the image if so!) But I doubt you will get a definite answer from them on anything until they've had a chance to mark the papers and judge the responses on it. I think if you wrote about packaging in vesicles and release from the organelle membrane, you will maybe get a mark or two regardless of which one you put.

    In the meantime, let's hope everyone nets lots of marks on Unit 5.
    Offline

    0
    ReputationRep:
    Can someone send me a link to the pre release please ?
    Offline

    2
    ReputationRep:
    (Original post by Browns10)
    Can someone send me a link to the pre release please ?
    http://moodle.nks.kent.sch.uk/plugin...th%20PROOF.pdf

    It has red lines all over it, but if you download and save it to your computer, the red lines disappear.
    Offline

    0
    ReputationRep:
    Will we get copy of the prerelease again during the exam or do we need to memorise all the specific parts?
    Offline

    2
    ReputationRep:
    Does anyone else feel like as long as you get the jist of the article it's best to just know the all the spec points really well and the article shouldn't really matter as long as you know all the key content ? I don't want to get bogged down these last 2 days reading the article aimlessly when I could be doing the actual content
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Should Spain allow Catalonia to declare independence?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.