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A2 Biology OCR June 2015 Revision Thread

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Original post by Maham88
is the electron transport chain part of chemiosmosis ?


Sort of. The ETC itself isn't chemiosmosis, but the product of ETC (the proton gradient) is.

Original post by Shanahey
Can someone please explain to me local currents/circuits?? (neurones)
Thank you :smile:


Local currents are when Na ions diffuse slightly sideways in action potentials. When they diffuse in the direction without a refractory period (the resting section), there is a new threshold gradient. This small distance is a local current.
Original post by TheLegalDealer
What on earth is that on about ???


Thats F212 which was last week :smile:
Original post by Beni24
Thats F212 which was last week :smile:


Was that in a f324" paper ?? And what AS topics could they ask us ?
Reply 1503
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tewas
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Original post by Maham88
why is the theoretical max yield of ATP per molecule of glucose hardly reached in aerobic respiration ?


ATP is required to actively transport pyruvate into the mitochondria
ATP is needed to shuttle H atoms on NADH to oxidative phosphorylation
ATP may leak through the membranes so reduces the number of H+ ions used during chemiosmosis so less ATP is generated
Original post by Maham88
why is the theoretical max yield of ATP per molecule of glucose hardly reached in aerobic respiration ?


ATP used to actively transport pyruvate from cytoplasm into mitochondria and Reduced NAD from gylcolysis to innermitochondial membrne

+ some protons leak through inner mitochondrial membrane so protomotive force reduced to make ATP
Hey everyone.

Respiratory substrates question - if the RQ is 0.75, is this lipid of proteins? Saw it on a past paper along with 0.95) and just didn't understand the mark scheme!

Thanks,

Good luck everyone!
if you write fructose (1,6) diphosphate instead of fructose (1,6) bisphosphate would that be right ?
Original post by daisystones
Hey everyone. <br />
<br />
Respiratory substrates question - if the RQ is 0.75, is this lipid of proteins? Saw it on a past paper along with 0.95) and just didn't understand the mark scheme!<br />
<br />
Thanks
<br />
Good luck everyone!


It will be a combination of the 3 but predominantly lipids due to depleted glucose availability.

You probably always get a mark for saying that proteins are an unlikely substrate
Original post by TheLegalDealer
Was that in a f324&quot; paper ?? And what AS topics could they ask us ?


Literally anything. I came across a unit 5 paper that talked about transpiration stream
Original post by loperdoper
I would say it's worth being aware of the basics of the method (just in case they throw in an application of knowledge question), although learning it until you can design it perfectly or anything is just a waste of time.


Thanks, much appreciated dude.
Original post by HeyThereHarry
Outline the use of biochemical tests to determine the presence of biological molecules in a solution. (5)


Hi, what past paper is this from? Seems quite a vague question so just want to see the context its been put in? Thanks
Could someone please explain what we need to know about respiratory substrates and RQs? (:
Useful link with mistakes in the OCR heinamann textbook (with the brain on front), just so then no one learns anything wrong! Worst thing is finding out you've made a mistake, with no fault of yours!

https://www.whatdotheyknow.com/request/textbook_errors_and_futyre_exam

Hope you find it helpful!
Original post by goonieskellie
Could someone please explain what we need to know about respiratory substrates and RQs? (:


The spec says
"Define the term respiratory substrate.
Explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates."

The first one is pretty self explanatory. The second you want to know that lipids have the most, as they have more hydrogen (reduce more NAD per molecule). Carbohydrates are used first as they can enter glycolysis straight away, whereas protein/lipids have to be broken down into glycerol/glucose first.
Do we need to know about peritoneal dialysis in detail ?


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Reply 1515
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Yua
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im scared
Original post by AsianBeauty
Do we need to know about peritoneal dialysis in detail ?


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The spec only refers to renal dialysis, and peritoneal dialysis doesn't even appear in the cgp student book, so I wouldn't worry about it.
Can someone tell me how to get A*?


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Sorry if this has been asked before, haven't read the other pages, what sort of topics are likely to come up?
What didn't come up in last year's paper
Original post by loperdoper
The spec only refers to renal dialysis, and peritoneal dialysis doesn't even appear in the cgp student book, so I wouldn't worry about it.


Thank you:smile:


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