Mass Flow Hypothesis

@nightcrawl3r has given you a good answer there

I'm not sure what exam board you're on but I'm on OCR and this is what we were taught


- The H+ ions are transported out via a proton pump using ATP from the companion cell to the outside cell (eg palisade cell) - active transport is used here because there is a higher H+ ion concentration on the outside cell than there is in the companion cell
- H+ ions goes with sucrose together at the same time from the outside cell to the companion cell. They bind to the sucrose H+ cotransporter so both the H+ and sucrose is now in the companion cell. Sucrose cannot move into the companion cell unless using a co-transporter as theres a higher sucrose level in the companion cell than the outside cell (so requires atp)
- sucrose then moves from the companion cell to the sieve tube via hydrolysis of atp because again, there is already a high sucrose concentration in the sieve tube.

- I'd assume the sucrose produced by photosynthesis in palisade cells are transported into companion cell by facilitated diffusion, as wel as having the proton pumps etc as it needs to maintain a concentration gradient


Mr pollock does quite a good video imo

Thank you . I am doing AQA but this still applies. Thanks again

no worries! pm if u need help on anything I think our exam boards overlap quite a bit

If you could post study help on the public forums rather than doing it via private PMs, it could help a lot more people....

will do! it's actually good way of revision haha

@Reality Check
Quick question unrelated to mass flow.
I am doing an EPQ on medicine in Year 13. My topic choice was Heart Disease - I was fascinated by high blood pressure in the UK. Does it count as a topic that overlaps with A level Biology? Is it a good EPQ topic? Is it to broad of a topic? Should I narrow it down like looking at the trend in the UK for the past 30 years? I am very confused with the title

Hi,

It's a good topic - and I think you could avoid too much overlap. From memory, the AQA specification doesn't go into great detail on HT. You just need to get the right angle on this topic, and of course your EPQ supervisor should be able to advise on this. However, you're right to narrow it down - a good EPQ topic has a tight focus and is achievable, rather than overly-broad and attempting to cover too much ground.It's an area on which I've done a fair bit of work, so I'd always encourage you on it

What sort of angle were you thinking of? The epidemiology of it? Clinical sequelae? The pathophysiology of it?

Thanks for the reply!

I was inclined into looking at the epidemiology but now that you mention it I am more eager to research on the " pathophysiology" - since I can talk more about the science behind it.

After doing some short research I can find more information on the pathophysiology of HT.

It would be a good angle if you're interested in the science of it. Why not talk to your EPQ supervisor about it and get back to me - we can discuss it more here, or you can make a dedicated EPQ thread for yourself.

So I was able to chase my EpQ supervisor ( also, Head of year 13) and had a 10min discussion about it . He said that it is okay, gave me some advice on how to approach the EPQ, in terms of title - he said keep it simple and narrow, showed me some past EPQs from old students . I forgot to ask him , does the title have to be a question ?
I was thinking of a very simple question like looking at the pathophysiology of HT in the UK. Or the trend of the Pathophsilogy of HT in the UK between 1980-2015 . Idk the title is so hard

Good that you've chosen an EPQ supervisor. The title doesn't have to be a question, though it usually is so you've got a focus for your writing.

I'm afraid the question 'look(ing) at the pathophysiology of HT in the UK' is far from simple - you could write a Ph.D. thesis on this (and many have)! You need to try to narrow it down much further - perhaps look at the links between HT and T2DM, or between HT and stroke/TIA incidence. Maybe look at a correlation between BMI and HT? Or maybe look to see if there's any differences in ethnicity.

Wow!
I might look at T2DM. I feel there’s lots of information on T2 diabetes on the internet to help me.


I can’t emphasise how much you are helping me so many thanks. !!