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OCR Biology F214 Communication, Homeostasis and Energy Wed 25 Jan 2012

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Reply 180
Only started revising this yesterday (yikes) but its my second time and i know a fair bit. Just a quick question, when blood glucose conc is too low the Glucagon binds to the Glucagon receptor on the hepatocyte but what enzyme converts the ATP into cAMP? is it Adenyl Cyclase again as it was the enzyme for when Insulin binds with the hepatocyte.
Original post by atman7
Only started revising this yesterday (yikes) but its my second time and i know a fair bit. Just a quick question, when blood glucose conc is too low the Glucagon binds to the Glucagon receptor on the hepatocyte but what enzyme converts the ATP into cAMP? is it Adenyl Cyclase again as it was the enzyme for when Insulin binds with the hepatocyte.


Yes
Reply 182
Original post by atman7
Only started revising this yesterday (yikes) but its my second time and i know a fair bit. Just a quick question, when blood glucose conc is too low the Glucagon binds to the Glucagon receptor on the hepatocyte but what enzyme converts the ATP into cAMP? is it Adenyl Cyclase again as it was the enzyme for when Insulin binds with the hepatocyte.


What iv been taught is:
when the levels are low, glycogen is released from alpha cells and travels in the blood til it reaches heptocytes where it bind with the receptors and results in glycogenolysis, gluconeogenesis, basically glucose is made.

Andd.....

the cAMP thing is for adrenanline, which results in enzyme activation of kinase a and phosphorlase, resulting in glucose forming?!

Cuz, alpha cells release glycogen not adrenaline..

Correct me if im wrong pleasee!
Original post by Lalaa
What iv been taught is:
when the levels are low, glycogen is released from alpha cells and travels in the blood til it reaches heptocytes where it bind with the receptors and results in glycogenolysis, gluconeogenesis, basically glucose is made.

Andd.....

the cAMP thing is for adrenanline, which results in enzyme activation of kinase a and phosphorlase, resulting in glucose forming?!

Cuz, alpha cells release glycogen not adrenaline..

Correct me if im wrong pleasee!


adrenaline has to use a secondary messenger because it is a peptide hormone so it can diffuse into the cell as it is impermeable to the phospholipid bilayer as opposed to the lipid hormomes which can diffuse directly into the cells.

glucagon is also a peptide hormone so it must use some sort of secondary messenger system but it doesn't mention in the book the exact details.

therefore we can either assume its the same as for adrenaline or we don't need to know the exact details
Reply 184
Original post by Lalaa
What iv been taught is:
when the levels are low, glycogen is released from alpha cells and travels in the blood til it reaches heptocytes where it bind with the receptors and results in glycogenolysis, gluconeogenesis, basically glucose is made.

Andd.....

the cAMP thing is for adrenanline, which results in enzyme activation of kinase a and phosphorlase, resulting in glucose forming?!

Cuz, alpha cells release glycogen not adrenaline..

Correct me if im wrong pleasee!


I read on an old spec mark scheme the enzyme is called phosphorylase which isn't needed to be known now I was just curious since the book didn't say anything and I wasn't sure If it was adenyl cyclase or not.

After doing a few questions I've found that you can get basically three marks for saying gluconeogensis glycogenlysis and that more fats are respired which is Pretty good since the questions are usually 5/6 mark Q's
Original post by undertaker1
adrenaline has to use a secondary messenger because it is a peptide hormone so it can diffuse into the cell as it is impermeable to the phospholipid bilayer as opposed to the lipid hormomes which can diffuse directly into the cells.

glucagon is also a peptide hormone so it must use some sort of secondary messenger system but it doesn't mention in the book the exact details.

therefore we can either assume its the same as for adrenaline or we don't need to know the exact details

Original post by atman7
I read on an old spec mark scheme the enzyme is called phosphorylase which isn't needed to be known now I was just curious since the book didn't say anything and I wasn't sure If it was adenyl cyclase or not.

After doing a few questions I've found that you can get basically three marks for saying gluconeogensis glycogenlysis and that more fats are respired which is Pretty good since the questions are usually 5/6 mark Q's

Adenyl cyclase turns ATP to cAMP, cAMP activates the kinase enzyme which in turn activates the phosphorylase enzyme which does the actual hydrolysis of glycogen into glucose.
Reply 186
Original post by The Illuminati
Adenyl cyclase turns ATP to cAMP, cAMP activates the kinase enzyme which in turn activates the phosphorylase enzyme which does the actual hydrolysis of glycogen into glucose.



Ahh thanks I didn't know that :smile:
Original post by The Illuminati
Adenyl cyclase turns ATP to cAMP, cAMP activates the kinase enzyme which in turn activates the phosphorylase enzyme which does the actual hydrolysis of glycogen into glucose.


which book is this from-- the big book doesnt mention kinase enzymes nor phosphorylase enzyme
Original post by undertaker1
which book is this from-- the big book doesnt mention kinase enzymes nor phosphorylase enzyme


old spec MS, can't remember the year but i copied it into my notes in case i need extra QWC points :tongue: we don't need to know it though. My OCR revision book says cAMP "activates a cascade of enzyme reactions", these are the enzymes.



Original post by atman7
Ahh thanks I didn't know that :smile:

you don't need to either but I learnt it so I can show off to the examiner so they may be more lenient :tongue:
can we start discussing the how science works part of the paper because i think this is the section where everyone struggles and looses marks.

i feel the how science works will be on proving the evidence for chemiosmosis this year
Reply 190
Original post by undertaker1
can we start discussing the how science works part of the paper because i think this is the section where everyone struggles and looses marks.

i feel the how science works will be on proving the evidence for chemiosmosis this year


I think the same it hasn't been up at all yet, how much "how science works" is there in the book? i can only remember the stuff on photosynthesis experiments and the evidence for chemiosmosis. And I'm sure something came up on photosynthesis in the June 2011 although I've not done that yet.

Expect a few synoptic marks as always, isn't there meant to be some stretch and challenge style questions on the A2 papers now there longer or did I misread that somewhere?
Reply 191
Original post by undertaker1
can we start discussing the how science works part of the paper because i think this is the section where everyone struggles and looses marks.

i feel the how science works will be on proving the evidence for chemiosmosis this year


Ye, i think chemiosmosis will come up! i find it sooo confusing! what evidence is there for chemiosmosis, and what is chemiosmosis?
Original post by atman7
I think the same it hasn't been up at all yet, how much "how science works" is there in the book? i can only remember the stuff on photosynthesis experiments and the evidence for chemiosmosis. And I'm sure something came up on photosynthesis in the June 2011 although I've not done that yet.

Expect a few synoptic marks as always, isn't there meant to be some stretch and challenge style questions on the A2 papers now there longer or did I misread that somewhere?


and there's renal dialysis but i feel its going to chemiosmosis because last paper didnt have much respiration on it either
Hi,

Just a bit confused on respiration. Why doesn't the krebs cycle nor link reaction continue in the absence of oxygen?! Oxygen is not used directly... Is it something to do with oxidative phosphorylation? :frown:
Reply 194
Original post by jamesandrew93
Hi,

Just a bit confused on respiration. Why doesn't the krebs cycle nor link reaction continue in the absence of oxygen?! Oxygen is not used directly... Is it something to do with oxidative phosphorylation? :frown:


Ye, it works backwards !

Oxygen is the final hydrgoen /electron acceptor, if there is on oxygen nothing to accpet, therefore, no kreb / link reaction occurs.

I think thats it ^?!
Reply 195
Original post by undertaker1
and there's renal dialysis but i feel its going to chemiosmosis because last paper didnt have much respiration on it either


it chemiosmosis just the movement of protons across thylakoid membranes and cristae?

renal dialysis might not coem up, im not sure what year it was, but there was a good 6-7 marks in total for just that -_-!
Original post by Lalaa
it chemiosmosis just the movement of protons across thylakoid membranes and cristae?

renal dialysis might not coem up, im not sure what year it was, but there was a good 6-7 marks in total for just that -_-!


yeh thats it
Original post by Lalaa
Ye, it works backwards !

Oxygen is the final hydrgoen /electron acceptor, if there is on oxygen nothing to accpet, therefore, no kreb / link reaction occurs.

I think thats it ^?!


So, if there is no oxygen then the reduced NAD can not be oxidised during oxidative phosporylation? Hence, it can not be reduced during the krebs cycle?

Respiration is sooooo confusing!
Reply 198
Original post by jamesandrew93
So, if there is no oxygen then the reduced NAD can not be oxidised during oxidative phosporylation? Hence, it can not be reduced during the krebs cycle?

Respiration is sooooo confusing!



i checked in a book : answer:
Aerobic resp. can only take place when oygen is present. this is beacause oxygen is the final electorn acceptor from the electorn transport chain. if there is no oxygen, then electorns cannot be passed in the electorn carriers so they cannot accept any more from NAHD, so the NADH cannot be converted to NAD, therefore there is nothing left to pick up hydrogen from reactions of link and krebs, and the electron transport chain grinds to a halt !

sorry about spellings and hope this makes sense ! ^?!:smile:
Reply 199
Original post by undertaker1
yeh thats it


the evidence for it, do you thinkyou would need to know how to do the experiments

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