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master y
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can anyone explain to me the difference between net prodictivity and gross productivity
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lcj0503
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#102
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(Original post by master y)
can anyone explain to me the difference between net prodictivity and gross productivity
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igloo1
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#103
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Can someone help me with respiration?
in the ETC it says it uses hydrogen atoms that have been made from glycolysis and the Krebs cycle. I see where the hydrogen atoms are made in glycolysis.
My problem is in one paragraph of the book, it says the Krebs cycle is important because it produced hydrogen that are carried by NAD. Yet in the diagram above it, it shows NAD being reduced into NADH. So surely hydrogen is needed to catalyse that reaction, like in photosynthesis.
I AM SO CONFUSED.
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amarjit700
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#104
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(Original post by master y)
can anyone explain to me the difference between net prodictivity and gross productivity
Net is the actual amount available after the plant has respired and lost energy, gross is the total amount available at the start so 'net production = gross production - respiratory losses'


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k1rby
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#105
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#105
(Original post by igloo1)
Can someone help me with respiration?
in the ETC it says it uses hydrogen atoms that have been made from glycolysis and the Krebs cycle. I see where the hydrogen atoms are made in glycolysis.
My problem is in one paragraph of the book, it says the Krebs cycle is important because it produced hydrogen that are carried by NAD. Yet in the diagram above it, it shows NAD being reduced into NADH. So surely hydrogen is needed to catalyse that reaction, like in photosynthesis.
I AM SO CONFUSED.
NAD combines with the hydrogen atom causing it to become NADH/reduced NAD. We say NAD is reduced by this combination because reduction is defined as the 'gain of electrons or gain of hydrogen or loss of oxygen'. Does that help at all?
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igloo1
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#106
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(Original post by k1rby)
NAD combines with the hydrogen atom causing it to become NADH/reduced NAD. We say NAD is reduced by this combination because reduction is defined as the 'gain of electrons or gain of hydrogen or loss of oxygen'. Does that help at all?
Kind of.. so are you saying that NAD is reduced the gain of electrons ( from where?) therefore hydrogen is made?
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master y
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#107
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for jan 2012 5ai could i say 1 & 2 who had hair had a child which was hairless, this meanth hat 1 & 2 were heterozygous... how many marks would i get?
(Original post by igloo1)
Kind of.. so are you saying that NAD is reduced the gain of electrons ( from where?) therefore hydrogen is made?

(Original post by k1rby)
NAD combines with the hydrogen atom causing it to become NADH/reduced NAD. We say NAD is reduced by this combination because reduction is defined as the 'gain of electrons or gain of hydrogen or loss of oxygen'. Does that help at all?

(Original post by amarjit700)
Net is the actual amount available after the plant has respired and lost energy, gross is the total amount available at the start so 'net production = gross production - respiratory losses'


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k1rby
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#108
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(Original post by igloo1)
Kind of.. so are you saying that NAD is reduced the gain of electrons ( from where?) therefore hydrogen is made?
No, it is reduced because it gains a hydrogen atom (which is one of the definitions for reduction, notice the 'or'). The hydrogen atom will have come off the triose phosphate molecule, during the process of it being turned into pyruvate, and then the hydrogen atom combines with NAD. Anything that gains hydrogen is said to be reduced. Anything that loses a hydrogen is said to be oxidised. Feel free to ask more questions if you still don't get it (it's good practice for me )


(Original post by master y)
for jan 2012 5ai could i say 1 & 2 who had hair had a child which was hairless, this meanth hat 1 & 2 were heterozygous... how many marks would i get?
You would get two marks because you've said that
  • Number 2 has hair but one of their offspring does not
  • Therefore 2 is heterozygous

It doesn't matter that you've mentioned 1 because it says 'ignore references to 1 and 6.' This is because the gene is carried on the X chromosome, so males can't be heterozygous. They are unaffected males meaning they don't have the hairless allele at all.
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kingpro88
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#109
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Hi guys, you see the 4markers and the 6marker ( the larger questions) can you write the answers in bullet points. I mean it does say QoWC is assed in ALL questions but ive never really seen it in the mark schemes. So would they 'deduct' marks if you write in bullet point for the larger/longer questions. I mean if the question is on Light dependant stage can you not just write bullet points ?
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Starlight94
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#110
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#110
Sorry if it's already been posted but does anyone have the jan 2013 paper and mark scheme?
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emah123
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#111
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#111
guys im planning to do 2 days solid revision for this retake exam? will that be enough to get an A?
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master y
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#112
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(Original post by emah123)
guys im planning to do 2 days solid revision for this retake exam? will that be enough to get an A?
yeah. what did u get in jan?
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emah123
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#113
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#113
(Original post by master y)
yeah. what did u get in jan?
i got a B
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master y
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#114
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(Original post by emah123)
i got a B
surely it can overall cancel out and become an A if your AS marks are high..also did you revise a lot in jan?
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#115
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(Original post by master y)
surely it can overall cancel out and become an A if your AS marks are high..also did you revise a lot in jan?
i am on the border of an A at AS and i did revise alot but made stupid mistakes in the exam
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TH4RG3
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#116
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Do we need to know about the photosystems? It doesnt mention it in the spec, cyclic and non-cyclic are not mentioned either but some text books and revision books seem to include it? Has it ever come up in a paper?
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Chewy29
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#117
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(Original post by TH4RG3)
Do we need to know about the photosystems? It doesnt mention it in the spec, cyclic and non-cyclic are not mentioned either but some text books and revision books seem to include it? Has it ever come up in a paper?
We dont need to know about photosystems on our exam board anymore.

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TH4RG3
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#118
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(Original post by Chewy29)
We dont need to know about photosystems on our exam board anymore.

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Thanks so much!!

Its irritating how much stuff there is in textbooks and revision books that we don't actually need to know...

But the specification seems to get some things wrong.. it says the Electron Transport Chain during the Light-Dependant Reaction is in the chloroplast Membrane, when it is actually in the thylakoid membrane..
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amarjit700
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#119
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(Original post by kingpro88)
Hi guys, you see the 4markers and the 6marker ( the larger questions) can you write the answers in bullet points. I mean it does say QoWC is assed in ALL questions but ive never really seen it in the mark schemes. So would they 'deduct' marks if you write in bullet point for the larger/longer questions. I mean if the question is on Light dependant stage can you not just write bullet points ?
Well tbh it would be better to write short structured sentences that not only link logically, but also contain the underlined Keyword from the mark scheme. You never know with bio 4 :/ also it doesn't have to be In exact order as I got my paper back and like say if theirs 7 marking points for a 5 marker I had got like mark points 1 3 4 and 6 so that's 4marks out of 5.


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flyylikejetz
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#120
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Can someone help me with question 2 (b) (i) & 2 (b) (ii) .. http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF
I just don't understand how to answer these questions
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