Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    Got a bit confused with this question in a recent past paper:

    "Explain how acetate is metabolised by hepatocytes" [3 marks]

    I put that acetate is combined with the co-enzyme A to form acetyl co-enzyme A. What else do I need to include for the other 2 marks? (Bearing in mind the ethanol -> acetate steps were mentioned in the previous question)

    Maybe something to do with it happening in the cytosol or the actual mechanism of it? :confused:

    Also, exam board is OCR A2 F124

    PS. I can ask my teacher on Monday for a definite answer, just wondering what you'd put/how you'd explain it.

    Thanks (+ rep for good answers)
    Offline

    7
    ReputationRep:
    WOW. I'm studying for F214 as well...I would have been so screwed if that were my paper

    All i know is: Pyruvate is used to make acetyl CoA. Each pyruvic acid molecule is broken down to form carbon dioxide and a 2-carbon acetyl group, which enters the Krebs cycle. Pyruvic acid is converted to acetyl coenzyme A with production of CO2, as welll reduction of NAD to NADH and H+

    i THINK :P
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by nevetstreblig)
    WOW. I'm studying for F214 as well...I would have been so screwed if that were my paper

    All i know is: Pyruvate is used to make acetyl CoA. Each pyruvic acid molecule is broken down to form carbon dioxide and a 2-carbon acetyl group, which enters the Krebs cycle. Pyruvic acid is converted to acetyl coenzyme A with production of CO2, as welll reduction of NAD to NADH and H+

    i THINK :P
    I would +1 you for your contribution, but I'm all out for the day!

    See that's what I was confused about...doesn't all that stuff you've mentioned take part in mitochondria or something? :confused: Acetyl co-enzyme A ends up being used in respiration, but that doesn't really show how hepatocytes metabolise it. :zomg:

    Horrible question.

    Thanks again for your response
    Offline

    7
    ReputationRep:
    All i can add really is: Acetate --> Acetyl CoA. CoA transfer Acetete from the Link Reaction --> Krebs. That's all i know -_- stupid OCR
    Offline

    19
    ReputationRep:
    Not sure quite what they're looking for in the question - what nevetstreblig noted about the role of acetate in aerobic respiration seems right at a glance, but then why specify in the hepatocytes?

    Regarding acetate, it's once again hard to read for an A-level question. If we're talking about acetate the anion when in combination in a compound, then it is involved in pretty much anything that Acetyl-CoA is involved in, so the whole pyruvate/Acetyl-CoA stuff may be what they're looking for - not a clear question though, huh? Especially because in Acetyl-CoA it takes the form of an acetyl group instead, dropping its O- to bind to the S of the CoA...

    Hopefully the examiners haven't got it mixed up with acetone production in the liver during fat metabolism in the fasted state; arguably acetate is involved since Acetyl-CoA gets converted into ketone bodies but once again it's acetone that's produced and the acetate in A-CoA is in the form of acetyl, so I'm really not sure what specifically the idiots at OCR are asking about.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Friar Chris)
    Not sure quite what they're looking for in the question - what nevetstreblig noted about the role of acetate in aerobic respiration seems right at a glance, but then why specify in the hepatocytes?

    Regarding acetate, it's once again hard to read for an A-level question. If we're talking about acetate the anion when in combination in a compound, then it is involved in pretty much anything that Acetyl-CoA is involved in, so the whole pyruvate/Acetyl-CoA stuff may be what they're looking for - not a clear question though, huh? Especially because in Acetyl-CoA it takes the form of an acetyl group instead, dropping its O- to bind to the S of the CoA...

    Hopefully the examiners haven't got it mixed up with acetone production in the liver during fat metabolism in the fasted state; arguably acetate is involved since Acetyl-CoA gets converted into ketone bodies but once again it's acetone that's produced and the acetate in A-CoA is in the form of acetyl, so I'm really not sure what specifically the idiots at OCR are asking about.
    Thanks for the reply

    We're going through it in class on Monday/Tuesday so hopefully I'll get a definitive answer, it's an odd number of marks to give to something. 3 marks is too much for just saying "it happens in the cytosol and acetyl coenzyme A blahblah" but not enough to go through everything you two have said...:confused:

    I'll post "the answer" on here when I get it...hopefully. :zomg:
    Offline

    7
    ReputationRep:
    Thanks for the reply

    We're going through it in class on Monday/Tuesday so hopefully I'll get a definitive answer, it's an odd number of marks to give to something. 3 marks is too much for just saying "it happens in the cytosol and acetyl coenzyme A blahblah" but not enough to go through everything you two have said...:confused:

    I'll post "the answer" on here when I get it...hopefully. :zomg:
    Looking forward to it :P
    • Thread Starter
    Offline

    2
    ReputationRep:
    Update, got the definitive answer:

    Acetate is combined with coenzyme A to form acetyl-coenzyme A (1 mark). This is then used in respiration (1 mark) to produce ATP (1 mark).

    Still an odd mark scheme but that's OCR for you.
    Offline

    19
    ReputationRep:
    (Original post by Joseppea)
    Update, got the definitive answer:

    Acetate is combined with coenzyme A to form acetyl-coenzyme A (1 mark). This is then used in respiration (1 mark) to produce ATP (1 mark).

    Still an odd mark scheme but that's OCR for you.
    Some examiner who is disappointed with his job probably thought he was being a bit of a smart-ass by writing 'hepatocyte' ('liver cell') to make up for his lack of an actual research position or whatever...

    Because Pyruvate dehydrogenation occurs in virtually all human cells (if not all of them, actually) and is a fundamental part of aerobic respiration and is the first major step of it that occurs in the mitochondrion...

    A-level exam boards really are up their own arses.
    Offline

    7
    ReputationRep:
    ...wow. That's an odd angle to answer the question...and an odd qn at that!
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Friar Chris)
    Some examiner who is disappointed with his job probably thought he was being a bit of a smart-ass by writing 'hepatocyte' ('liver cell') to make up for his lack of an actual research position or whatever...

    Because Pyruvate dehydrogenation occurs in virtually all human cells (if not all of them, actually) and is a fundamental part of aerobic respiration and is the first major step of it that occurs in the mitochondrion...

    A-level exam boards really are up their own arses.
    Exactly, the "hepatocyte" bit threw me completely. Maybe in OCR's world, only hepatocytes respire and the examiners are all secretly just massive livers?
    Offline

    19
    ReputationRep:
    (Original post by Joseppea)
    Exactly, the "hepatocyte" bit threw me completely. Maybe in OCR's world, only hepatocytes respire and the examiners are all secretly just massive livers?
    Perhaps. Hepatocytes are one of a number of different cell types that make up the liver tissue; though as their name suggests ('hepato' is from the Greek for 'liver', and 'cyte', derived into English use for 'cell') hepatocytes make up the bulk of the liver.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Friar Chris)
    Perhaps. Hepatocytes are one of a number of different cell types that make up the liver tissue; though as their name suggests ('hepato' is from the Greek for 'liver', and 'cyte', derived into English use for 'cell') hepatocytes make up the bulk of the liver.
    Oh no I realise that. I wasn't seriously suggesting that these odd liver-people could exist...I mean, they wouldn't even have a blood supply so probably wouldn't function well enough to mark an exam.

    PS. I know that livers are made up of more than one type of cell. xD
    Offline

    19
    ReputationRep:
    I was merely attempting to address:

    (Original post by Joseppea)
    Exactly, the "hepatocyte" bit threw me completely.
    the quotations sounded as if the notion of hepatocyte was alien in addition to its admittedly ridiculous inclusion in the question.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Friar Chris)
    I was merely attempting to address:



    the quotations sounded as if the notion of hepatocyte was alien in addition to its admittedly ridiculous inclusion in the question.
    Ah I see - no, I knew what a hepatocyte was, I was just confused about the mark scheme etc.
 
 
 

University open days

  • University of Roehampton
    All departments Undergraduate
    Sat, 17 Nov '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 17 Nov '18
  • Bournemouth University
    Undergraduate Open Day Undergraduate
    Sat, 17 Nov '18
Poll
Black Friday: Yay or Nay?

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.