transport across membranes AQA bio a level help

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idk__21
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#1
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#1
This is what the mark scheme says but wouldnt it be active transport as there is a lower concentration of potassium ions outside the cell than inside so it moves from a low to high conc? Any help is appreciated, thanks
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HarisMalik98
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#2
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#2
Active Transport is correct.

Looks to me like the MS has forgot to indicate that the first mark should be for stating Active Transport!
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macpatgh-Sheldon
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#3
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(Original post by idk__21)
This is what the mark scheme says but wouldnt it be active transport as there is a lower concentration of potassium ions outside the cell than inside so it moves from a low to high conc? Any help is appreciated, thanks
Yes correct you do not know lol!! - let me enlighten you - please read the first paragraph carefully - I believe the answer is diffusion - remember we are talking about bacteria here NOT humans [K+ higher intracellularly].
(Original post by HarisMalik98)
Active Transport is correct.

Looks to me like the MS has forgot to indicate that the first mark should be for stating Active Transport!
Mark schemes can be incorrect esp with Edexcel but not here!

M
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HarisMalik98
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Sorry but have to disagree, whilst there are some whacky modes of K+ transport in bacteria (which I learned at uni sadly), the major K+ uptake process is still primarily active transport; and considering this is A level, and there's no other evidence given in this passage to indicate otherwise, I think the MS has just missed out active transport. In some cases, K+ may move down a concentration gradient - however this is only when an electrochemical gradient has been established due to the coupling movement of other ions - which is still secondary active transport (and beyond A level anyway I'm assuming).
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HarisMalik98
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#5
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#5
By doing research, I've found that the question should be split into 2 parts. The MS you've received is an amalgamation of these two seperate parts - so it has indeed been written wrong.Name:  Screenshot_20220531-092757_OneDrive-compressed.jpg.jpeg
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The first part is active transport, and explaining because it's from low to high concentrations. The second part is the first part of your MS, rate of movement proportional to concentration gradient (high in cytoplasm, low in extracellular environment).
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macpatgh-Sheldon
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#6
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(Original post by HarisMalik98)
Sorry but have to disagree, whilst there are some whacky modes of K+ transport in bacteria (which I learned at uni sadly), the major K+ uptake process is still primarily active transport; and considering this is A level, and there's no other evidence given in this passage to indicate otherwise, I think the MS has just missed out active transport. In some cases, K+ may move down a concentration gradient - however this is only when an electrochemical gradient has been established due to the coupling movement of other ions - which is still secondary active transport (and beyond A level anyway I'm assuming).

.
HarisMalik98,
Hello there Mzee Haris, apologies to yourself, OP and other members!
I just perused this Q once, then gave my view, but was too laid back to go back with the headache of copying what I had already typed then coming back & pasting it so failed to note the word "inward" movement of K+, in the Q, and subconsciously assumed the opposite - oc both you guys are correct. Chances are this is an Edexcel Q on 2nd thought!!

M
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idk__21
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#7
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(Original post by HarisMalik98)
By doing research, I've found that the question should be split into 2 parts. The MS you've received is an amalgamation of these two seperate parts - so it has indeed been written wrong.Name:  Screenshot_20220531-092757_OneDrive-compressed.jpg.jpeg
Views: 16
Size:  109.6 KB

The first part is active transport, and explaining because it's from low to high concentrations. The second part is the first part of your MS, rate of movement proportional to concentration gradient (high in cytoplasm, low in extracellular environment).
(Original post by macpatgh-Sheldon)
Hello there Mzee Haris, apologies to yourself, OP and other members!
I just perused this Q once, then gave my view, but was too laid back to go back with the headache of copying what I had already typed then coming back & pasting it so failed to note the word "inward" movement of K+, in the Q, and subconsciously assumed the opposite - oc both you guys are correct. Chances are this is an Edexcel Q on 2nd thought!!

M
that makes sense, thanks a lot to both for the help!!
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