A2 Biology OCR June 2015 Revision Thread

Reply 1880

username1107011

1

Original post by cinderella25

That's all f215

Posted from TSR Mobile

Is it??? Thank god i've been revising ecology and conservation for tomorrow instead hahah

Reply 1881

nombo

13

Original post by TotalerReinfall

Can anyone help me with explaining how ATP isn't pushed out of the glomerulus via ultrafiltration in the liver?? :frown:

please

I don't think ATP gets to the glomerulus as it would have been used up. Hydrolysis of ATP is coupled with a reaction that requires energy (the energy given off by hydrolysis of ATP) so it would not get there. It would be a waste for it to be excreted. Anyway, it is probably too large to pass through the basement membrane, a mesh of collagen and glycoproteins that filters out molecules larger than 69,000RMM (a size of molecule) so it would not enter the Bowman's capsule.

Reply 1882

Lighfy

3

Original post by edsketch

Okay, something I'm really confused about, and I'm sure I'm not alone on this one. So the Electron Transport Chain is used during Non-Cyclic Phosphorylation, where light energy excites an e- which moves along the electron carriers losing energy.
But it's also used in animals with Respiration, during Oxidative Phosphorylation? What're the differences between the two? It's so confusing!

There is no difference. The electron transport chain refers to proteins embedded in the membranes, which undergo redox reactions when they accept and donate electrons.

Ultimately, they generate energy to pump protons into the inter membrane/thylakoid space for chemiosmosis.

Reply 1883

gh1290

1

Original post by TotalerReinfall

Is it??? Thank god i've been revising ecology and conservation for tomorrow instead hahah

also f215

Reply 1884

Star Light

14

Original post by TotalerReinfall

Can anyone help me with explaining how ATP isn't pushed out of the glomerulus via ultrafiltration in the liver?? :frown:

please

This is a tricky bit - ATP actually does technically leave the glomerulus during ultrafiltration in the liver capsule, as it's a small molecule with a RMM less than 69,000 so it can fit through the cellar membrane. However, ATP is a desired molecule, so as it passes through the nephron, in the distal hepatic tubule it depolarises the convoluted cells, so their nanovilli compartmentalise each ATP molecule in a phospholipid vesicle and re-absorb the ATP into the afferent arteriole via endocytosis, alongside the facilitated diffusion of Ca+ ions through a cotransporter in the stroma.

Hope this makes sense!

Reply 1885

hajs

11

After a prolonged period of fasting, glycogen levels in the liver are depleted. However the liver can still produce glucose by the process of gluconeogenesis. Describe one way in which this is done?

Anyone gonna try to answer that? I found it really difficult lol..

Reply 1886

WBN

Original post by DaveUncle

Omfg you're joking..... including stuff like gene therapy and electrophoresis??

yup, all you need to learn is communication, nerves, hormones, excretion(liver+kidney) , photosynthesis and respiration

Reply 1887

DaveUncle

3

Original post by WBN

yup, all you need to learn is communication, nerves, hormones, excretion(liver+kidney) , photosynthesis and respiration

oh okay i think im fine with all that anyway, does that include sympathetic and parasympathetic nerves then?

Reply 1888

WBN

Original post by DaveUncle

oh okay i think im fine with all that anyway, does that include sympathetic and parasympathetic nerves then?

no I dont think so

Reply 1889

it's a me, mario

2

Original post by DaveUncle

oh okay i think im fine with all that anyway, does that include sympathetic and parasympathetic nerves then?

How comes youre not sure what's in f214 and whats in f215?

Surely you have the ocr textbook, no?

Posted from TSR Mobile

Reply 1890

nombo

13

Original post by edsketch

Okay, something I'm really confused about, and I'm sure I'm not alone on this one. So the Electron Transport Chain is used during Non-Cyclic Phosphorylation, where light energy excites an e- which moves along the electron carriers losing energy.
But it's also used in animals with Respiration, during Oxidative Phosphorylation? What're the differences between the two? It's so confusing!

In the OCR book, they call the thing in photosynthesis 'electron carrier system' and the one in respiration 'electron transport chain'. I think they both do similar things and both release energy by it but that's the difference in names (in the book).

(edited 8 years ago)

Reply 1891

gh1290

1

Original post by DaveUncle

oh okay i think im fine with all that anyway, does that include sympathetic and parasympathetic nerves then?

also f215

Reply 1892

username1107011

1

Original post by Star Light

This is a tricky bit - ATP actually does technically leave the glomerulus during ultrafiltration in the liver capsule, as it's a small molecule with a RMM less than 69,000 so it can fit through the cellar membrane. However, ATP is a desired molecule, so as it passes through the nephron, in the distal hepatic tubule it depolarises the convoluted cells, so their nanovilli compartmentalise each ATP molecule in a phospholipid vesicle and re-absorb the ATP into the afferent arteriole via endocytosis, alongside the facilitated diffusion of Ca+ ions through a cotransporter in the stroma.

Hope this makes sense!

thank you omg!! you've saved my life!!!! :biggrin:

Reply 1893

ZQ110

5

Original post by TotalerReinfall

Can anyone help me with explaining how ATP isn't pushed out of the glomerulus via ultrafiltration in the liver?? :frown:

please

ATP is used up very quickly, as it's released in small packets of 30.6KJ so I doubt there will be a significant amount of ATP in the blood to start with?

Reply 1894

Lighfy

3

Original post by hajs

After a prolonged period of fasting, glycogen levels in the liver are depleted. However the liver can still produce glucose by the process of gluconeogenesis. Describe one way in which this is done?

Anyone gonna try to answer that? I found it really difficult lol..

Can't glucose be produced by combining fatty acids and amino acids together? :s-smilie:

Reply 1895

Munrot07

18

Original post by hajs

After a prolonged period of fasting, glycogen levels in the liver are depleted. However the liver can still produce glucose by the process of gluconeogenesis. Describe one way in which this is done?

Anyone gonna try to answer that? I found it really difficult lol..

Gluconeogenesis is the process of converting amino acids, fats and nucleic acids into glucose. Certain amino acids can be bled into the krebs cycle and then go through reverse glycolysis (bar a few reactions) and are turned back to glucose. Pyrimidines can do this as well (purines can not).

Reply 1896

alexthehuman

2

Im sorry if this has already been asked but im new to the thread. I can't find the 2014 f214 paper anywhere. Does anyone have it or know what the big questions were?

Reply 1897

loperdoper

15

Original post by baymax96

Ahhh tysm again!!! So helpful :smile:

Edit: how is there water in the ascending limb if the water is lost by osmosis in the descending limb?

I'm going to assume the main point is that not all the water is lost in the descending limb. The water potential gradient is there, but by the time it's passed into the ascending limb some of it hasn't diffused out into the capillaries yet. That's why ADH can have an affect to vary it - not all of the water diffuses out of the collecting duct either, so aquaporins can help it along a bit more.

Original post by alexthehuman

Im sorry if this has already been asked but im new to the thread. I can't find the 2014 f214 paper anywhere. Does anyone have it or know what the big questions were?

http://www.thebiotutor.com/past-papers3.html

(edited 8 years ago)

Reply 1898

gh1290

1

What is the purpose of the DCT?? can't find it anywhere in the book :angry:

, thanks

Reply 1899

coolerthanbeans

11

Original post by hajs

After a prolonged period of fasting, glycogen levels in the liver are depleted. However the liver can still produce glucose by the process of gluconeogenesis. Describe one way in which this is done?

Anyone gonna try to answer that? I found it really difficult lol..

amino acids + fats = glucose
= gluconeogenesis :smile:

A2 Biology OCR June 2015 Revision Thread

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