Turn on thread page Beta
    Offline

    3
    ReputationRep:
    (Original post by VickyDoodle)
    Can someone explain the Krebs Cycle to me please?
    Acetyl Coenzyme A is produced in the Link Reaction.
    This is a 2 carbon compound that combines with a 4 carbon compound to form a 6 carbon compound (Citrate).
    This 6 carbon compound then undergoes dehydrogenation and decarboxylation. This produces a 5 carbon compound (because decarboxylation meant it lost a carbon atom, producing carbon dioxide as a waste product). The lost hydrogens are picked up by NAD, producing reduced NAD.

    The 5 carbon compound then undergoes 1 decarboxylation, 1 substrate-level phosphorylation and 3 dehydrogenations.
    Hydrogens lost from 2 of the dehydrogenations is picked up by NAD and then hydrogens lost from the last dehydrogenation is picked up by FAD.

    These coenzymes (NAD and FAD) then carrier the hydrogens they have picked up to the electron transport chain.
    Offline

    3
    ReputationRep:
    (Original post by iesians)
    what is the structural difference b/w tendons and ligaments ??! (3 marks)
    Tendons join muscle to bone whereas ligaments join bone to bone.
    Ligaments are flexible to allow movement around the joint but tendons are inelastic.

    What else can you say? :unsure:
    Offline

    0
    ReputationRep:
    (Original post by SimpleGirl)
    Acetyl Coenzyme A is produced in the Link Reaction.
    This is a 2 carbon compound that combines with a 4 carbon compound to form a 6 carbon compound (Citrate).
    This 6 carbon compound then undergoes dehydrogenation and decarboxylation. This produces a 5 carbon compound (because decarboxylation meant it lost a carbon atom, producing carbon dioxide as a waste product). The lost hydrogens are picked up by NAD, producing reduced NAD.

    The 5 carbon compound then undergoes 1 decarboxylation, 1 substrate-level phosphorylation and 3 dehydrogenations.
    Hydrogens lost from 2 of the dehydrogenations is picked up by NAD and then hydrogens lost from the last dehydrogenation is picked up by FAD.

    These coenzymes (NAD and FAD) then carrier the hydrogens they have picked up to the electron transport chain.
    Oh so does dehydrogenation and decarboxylation occur after they have combined? (acetyle coenzyme A and the 4C compound) i thought a carbon is lost before it combines, i could be wrong :s


    This was posted from The Student Room's iPhone/iPad
    Offline

    0
    ReputationRep:
    In translation, after the amino acid chain is formed, what happens to the mRNA?
    Offline

    0
    ReputationRep:
    (Original post by 19941994)
    Oh so does dehydrogenation and decarboxylation occur after they have combined? (acetyle coenzyme A and the 4C compound) i thought a carbon is lost before it combines, i could be wrong :s


    This was posted from The Student Room's iPhone/iPad
    no that is correct !
    apparently CO2 is formed two times once in krebs cycle and once as you said in the link reaction when pyruvate (3C) is converted to acetyl (2C) !
    Offline

    0
    ReputationRep:
    Oh so does dehydrogenation and decarboxylation occur after they have combined? (acetyle coenzyme A and the 4C compound) i thought a carbon is lost before it combines, i could be wrong :s
    Dehydrogenation and decarboxylation occur before they combine.
    Offline

    0
    ReputationRep:
    apparently CO2 is formed two times once in krebs cycle and once as you said in the link reaction when pyruvate (3C) is converted to acetyl (2C) !
    Decarboxylation occurs twice in Krebs.
    Offline

    0
    ReputationRep:
    (Original post by iesians)
    no that is correct !
    apparently CO2 is formed two times once in krebs cycle and once as you said in the link reaction when pyruvate (3C) is converted to acetyl (2C) !
    Oh right, so is the CO2 formed when the pyruvate is alone or after it has combined with coenzyme A? :s if that makes sense lol


    This was posted from The Student Room's iPhone/iPad
    Offline

    0
    ReputationRep:
    (Original post by Omar1994)
    Decarboxylation occurs twice in Krebs.
    lol i know ! i combined the two decarboxylations of krebs cycle into one to make a comparison with the decarboxylation of link reaction !
    Offline

    0
    ReputationRep:
    Oh and i know two CO2 are released, but does the first one that is released come from pyruvate or acetyl coenzyme A?


    This was posted from The Student Room's iPhone/iPad
    Offline

    3
    ReputationRep:
    (Original post by 19941994)
    Oh so does dehydrogenation and decarboxylation occur after they have combined? (acetyle coenzyme A and the 4C compound) i thought a carbon is lost before it combines, i could be wrong :s


    This was posted from The Student Room's iPhone/iPad
    Pyruvate is produced in glycolysis, right? And that's a 3 carbon compound.
    It then moves to the mitochondria where the link reaction takes place immediately after.
    Here, pyruvate undergoes decarboxylation meaning it goes from a 3C to a 2C compound.
    It also undergoes dehydrogenation and the hydrogens are picked up by NAD.
    The 2C compound is called acetyl and it combines with a coenzyme (called Coenzyme A) and forms acetyl coenzyme A.

    So Acetyl coenzyme A is the 2 carbon compound produced by the end of the link reaction.
    Carbon dioxide is also produced due to the decarboxylation and reduced NAD is also produced due to the dehydrogenation.


    Now, the acetyl coenzyme A will initiate the Krebs cycle.

    Krebs Cycle:
    Acetyl Coenzyme A is produced in the Link Reaction.
    This is a 2 carbon compound that combines with a 4 carbon compound to form a 6 carbon compound (Citrate).
    This 6 carbon compound then undergoes dehydrogenation and decarboxylation. This produces a 5 carbon compound (because decarboxylation meant it lost a carbon atom, producing carbon dioxide as a waste product). The lost hydrogens are picked up by NAD, producing reduced NAD.

    The 5 carbon compound then undergoes another 1 decarboxylation, 1 substrate-level phosphorylation and another 3 dehydrogenations.
    Hydrogens lost from 2 of the dehydrogenations is picked up by NAD and then hydrogens lost from the last dehydrogenation is picked up by FAD.

    These coenzymes (NAD and FAD) then carrier the hydrogens they have picked up to the electron transport chain.

    Does that make more sense?
    Offline

    0
    ReputationRep:
    (Original post by 19941994)
    Oh right, so is the CO2 formed when the pyruvate is alone or after it has combined with coenzyme A? :s if that makes sense lol


    This was posted from The Student Room's iPhone/iPad
    NOT ALONE NOT AFTER.
    it is formed AS it is being converted to acetylcoenzyme A !
    thats why i quoted carbon numbers in both compounds !
    pyruvate has 3C and acetyl group has 2C so 1C is lost in CO2.
    Offline

    3
    ReputationRep:
    There are only two core practicals we need to learn, right?

    Can anyone give a summary of both of them, please?
    Offline

    0
    ReputationRep:
    There is so much that can come up :/
    Offline

    0
    ReputationRep:
    Thanks to simplegirl and iesians for clearing that up for me!!


    This was posted from The Student Room's iPhone/iPad
    Offline

    0
    ReputationRep:
    (Original post by Omar1994)
    There is so much that can come up :/
    Theres too much lol im so worried!


    This was posted from The Student Room's iPhone/iPad
    Offline

    0
    ReputationRep:
    so who finished solving the pastpapers??
    Offline

    3
    ReputationRep:
    (Original post by 19941994)
    Thanks to simplegirl and iesians for clearing that up for me!!


    This was posted from The Student Room's iPhone/iPad
    You're welcome
    Offline

    0
    ReputationRep:
    does anyone have the Jan 2012 Unit 5 paper and markscheme?
    Thanks in advance
    Offline

    0
    ReputationRep:
    (Original post by Terrorofgirlscouts)
    does anyone have the Jan 2012 Unit 5 paper and markscheme?
    Thanks in advance
    u can download the qu , ms and er from this link

    http://www.mediafire.com/?418nynasohiaa

 
 
 
The home of Results and Clearing

1,311

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  2. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
  3. Bishop Grosseteste University
    All Courses Undergraduate
    Fri, 17 Aug '18
Poll
Will you be tempted to trade up and get out of your firm offer on results day?

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

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