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A2 Biology OCR June 2015 Revision Thread

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Original post by emferrer
Hi,

does a high RQ like carbohydrates indicate more o2 consumed than co2 given off or is it less o2 consumed than given off??

help!


How much do we need to know about RQ values? It's not in the spec or my revision guide :/
Original post by emferrer
Hi,

does a high RQ like carbohydrates indicate more o2 consumed than co2 given off or is it less o2 consumed than given off??

help!


C6H12O6 + 6O2 --> 6H2O + 6CO2

Therefore a carboyhydrates have an RQ of 1, so they're equal.

Higher than 1 would be anaerobic

Lower than 1 would be fats/proteins which indivate more CO2 given off than O2 consumed
Original post by TheLegalDealer
can someone explain to me how an A.P, is transmitted along a non-myleinated neurone ? Thanks !

same way as a myelinated neurone. except without saltatory conduction, there is also more loss of potential to the outside of the neurone
Original post by emferrer
Hi,

does a high RQ like carbohydrates indicate more o2 consumed than co2 given off or is it less o2 consumed than given off??

help!


it is volume of CO2 given off over volume of O2 used. a high RQ would mean that a lot of CO2 is released with not that much O2 being used.
Reply 1703
Avatar for LA_95
LA_95
1
What's photorespiration?

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image.jpg

Scratch that, insulin secretion is probably not coming up (June 2011h
Original post by bballislife
same way as a myelinated neurone. except without saltatory conduction, there is also more loss of potential to the outside of the neurone.


A little more detail ? , I know you have to say Na+ channels open and Na+ diffuses sideways to areas of low conc. but would i say after that ?
image.jpg

Scratch that, insulin secretion is probably not coming up (June 2011)
Reply 1707
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Qui
2
Original post by maisie__x
How much do we need to know about RQ values? It's not in the spec or my revision guide :/

What revision guide are you using? It was in an exam a while back I remember seeing a question on it.
Original post by LA_95
What's photorespiration?

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Over 25 degrees, O2 competes for the active site of rubisco. When it does, photoresistion happens, which is more of less the opposite of photosynthesis
Original post by LA_95
What's photorespiration?

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its when rubisco takes up oxygen instead of CO2- post above says above 25c, not necessarily, Rubisco is crap at doing its job, its more likely to happen over 25c but I've forgotten why.EDIT: I've remembered, its because the stomata close up at 25c + and therefore the concentration of O2 builds inside cells making the plant more likely to undergo photorespiration.

Original post by TheLegalDealer
A little more detail ? , I know you have to say Na+ channels open and Na+ diffuses sideways to areas of low conc. but would i say after that ?

yeah so, as the electrotonic spread (the reason why the Na+ moves forward as they repel and spread out) reaches the voltage gated ion channels they open due to them reaching threshold potential, theyre set to about -50mv, (so obviously once the action potential reaches them they open) they then open and Na+ floods in, making it depolarised.
(edited 8 years ago)
Original post by AnnekaChan173
Over 25 degrees, O2 competes for the active site of rubisco. When it does, photoresistion happens, which is more of less the opposite of photosynthesis


do we need to know the details of photorespiration ?
Original post by Qui
What revision guide are you using? It was in an exam a while back I remember seeing a question on it.


Yeah i was able to answer that question though because there was a table given. I just wondered if we'd ever be asked to work out RQ value without being given a formula, or asked to state the RQ value of lipids? My revision guide is just 'OCR biology a2 - My revision notes' But it's written by the same guy who writes the text book and he also writes out f214 exam and wrote f211 last year. So i doubt it would leave anything out, but i saw a lot of talk about RQ values and got worried :/
Reply 1712
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hajs
11
Two questions:

1- Is O2 actively transported into the mitochondrial matrix? how does it end up there?
2- Is photolysis a hydrolysis reaction?

Thanks
Is timing an issue for anyone with this paper?
For the spec point:

"Describe the formation of urea in the liver, including an outline of the ornithine cycle."

What do we need to know about in relation to the Ornithine cycle?

I know:

amino acid + oxygen = keto acid + ammonia

ammonia + carbon dioxide = urea + water

Is that enough?
Original post by hajs
Two questions:

1- Is O2 actively transported into the mitochondrial matrix? how does it end up there?
2- Is photolysis a hydrolysis reaction?

Thanks


1 - As far as I know (and anyone please correct me if wrong) oxygen just diffuses. I don't think there is any need for active transport as oxygen can easily diffuse through membranes and going into the mitochondria wont be against its concentration gradient as it will be used pretty quickly.

2 - No. Hydrolysis is the breaking of a bond using water. Photolysis is the breaking of a bond (in this case, the bonds of water) using light.
Original post by Maham88
do we need to know the details of photorespiration ?


No :smile: It did come up in a paper once as a "outside the spec" topic but it will explain everything you need to know. Knowing the term wont hurt and the fact it is a bad thing for plants and stems from the awful structure of RuBisCO being able to accept oxygen. It might be good to know that C4 and CAM plants have mechanisms to stop photorespiration but bar that very basic amount of information I wouldn't worry about it.
Reply 1717
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LA_95
1
What exactly do we need to know about the beta oxidation pathway? Is there much in the revision guides because I can't find much? Is it to do with fatty liver/cirrhosis? What marking points do we need to know?

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Is this correct?
Type one diabetes is when beta cells are attacked by the boy's own immune system so cannot sufficiently produce insulin and so glucose cannot be converted to glycogen stores. This means when blood glucose concentrations are low, there is no glucose store to bring it back up to the ideal, and when blood glucose concentrations are high, the body isn't capable of storing the glucose as glycogen so glucose levels remain dangerously high.
Is that a decent explanation of type one diabetes?
Original post by TheLegalDealer
A little more detail ? , I know you have to say Na+ channels open and Na+ diffuses sideways to areas of low conc. but would i say after that ?


The Na+ ions have to diffuse along the entire length of the neurone, rather than just at the nodes of ranvier, so saltatory conduction does not occur

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