AQA BIOL4 ~ 11th June 2013 ~ A2 Biology

can anyone explain to me the difference between net prodictivity and gross productivity

can anyone explain to me the difference between net prodictivity and gross productivity

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?

Kind of.. so are you saying that NAD is reduced the gain of electrons ( from where?) therefore hydrogen is made?

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?

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'


Posted from TSR Mobile

Kind of.. so are you saying that NAD is reduced the gain of electrons ( from where?) therefore hydrogen is made?

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?

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?

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?

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.

Posted from TSR Mobile

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 ?