AQA A-Level Biology (7402) Exam Thread - June 12th, June 20th and June 26th

Agreed! I honestly can't understand how stupid the mark scheme can be sometimes in terms of how precise or rigid the answer must be and you're like "no one is EVER going to think to say this unless you've asked the exact same question before?!"
Like you say its just given that you're going to lost some marks just due to how stupidly pedantic they are, but i just tend to chuck a bunch of answers at them and hope that one of them is what they're looking for :P

This is neither helpful nor true. If the mark scheme wasn't rigorous, you'd be the first one to point the finger and start shouting the odds about how 'subjective' the marking is....

Mark schemes are rigorous for a reason - they enable fair and consistent marking against an agreed set of acceptable answers.

I wasn't complaining. Just pointing out there is no advantage to dwelling on the stress generated by missing marks even though you knew the answer, which happens all the time in biology.

Don't forget the ATP that's made via substrate-level phosphorylation during glycolysis - you've only mentioned the NADH + H⁺ and 2 x pyruvate here.

*basically purpose is to still supply ATP but only 2ATP molecules which is very low compared to anaerobic respiration * I did say that here just not explicitly, 2ATP produced from glycolysis (net gain). Pyruvate and red NAD doesn't make ATP

I don't really understand what you've written here, but are you suggesting that pyruvate and NADH doesn't go on to produce ATP period, or just via glycolysis?

in anaerobic respiration, the only ATP produced is from glycolysis- obviously the whole point in making lactate or ethanol and CO2... is to oxidise the NAD the the NAD is available again for glycolysis- so ATP can be generated over and over- if the red NAD wasn't oxidised, there would be a limited supply of NAD so a limited amount of glycolysis and so ATP

this is all just from my head, so don't quote me, but basically-

anaerobic = not enough o2
so glycolysis can happen but ONLY glycolysis
glycolysis produces 2x pyruvate molecules and 2x reduced NAD

IN ANIMALS; lactate is produced
so; pyruvate + red NAD ---> lactate + oxi NAD

IN PLANTS/YEAST;
pyruvate + red NAD --> CO2 + ethanol

basically purpose is to still supply ATP but only 2ATP molecules which is very low compared to anaerobic respiration
it is never one or the other, if there is low O2 then anaerobic resp will happen with a bit of aerobic respiration

it is good because it supplies some ATP but lactate builds up in muscles and causes muscle fatigue= bad

redNAD needs to be converted back to oxi NAD so it can be reused in glycolysis in the cytoplasm of cells


hope this makes sense- this is the basics and probably the only stuff you could get asked on it

during ultrafiltration what different layers does the glomerular filtrate pass through to reach the proximal convoluted tubule ? my class notes say different things to my text book , so confused

during ultrafiltration what different layers does the glomerular filtrate pass through to reach the proximal convoluted tubule ? my class notes say different things to my text book , so confused

endothelial cell, basement membrane, and the podocytes

do we need to know about cyclic photophosphorylation ?

yasss- all on the principle of gaps? letting smaller molecules OUT but not the large proteins and red blood cells?

do we need to know about cyclic photophosphorylation ?

Anything smaller than 69,000 RMM is forced out by ultrafiltration, including things like glucose. Large molecules like proteins are left behind as they are too large to pass through the membranes. Glucose should be reabsorbed in the PCT, if it isnt then thats a sign of diabetes

Yes, it is on our spec