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master y
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#1581
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#1581
(Original post by JenLivYoung)
Hey! From the mark scheme I was given by my teacher, I got told that there's only 2 extra marks for out of spec stuff, so personally I wouldn't stress about learning reams, just read round a bit and see if there's anything relevant that you could maybe include, but I wouldn't panic if you can't fit it in on the day
how are you reading around the subject? What sources are u using?
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lala12
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#1582
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#1582
(Original post by loveheartsandall)
Hi everyone, this is a question about unit 4 but I couldn't find the thread for it. I'm guessing you're all doing unit 4 or have done it anyway??? My school has decided to do the whole course at the end of the year ahhhhhhhhhhhhhhhh!


Anyway can anyone answer this question from the Jan 2011 Unit 4 paper?

"Residual food intake RFI is the different between the amount of food an animal actually eats and its expected food intake based on its size and growth rate. Scientists have selectively bred cattle for low RFI.

When RFI is calculated, low values are negative. Explain why there are negative."

WHY??? I've looked on the mark scheme and it says "amount of food take in is less than expected" but this doesn't make sense to me

Please can someone explain?? Many thanks
Well it might help if we add numbers to this. So say that the expected food intake is 15 arbitrary units. However, in reality, the animal only eats 10 arbitrary units. As RFI is Actual intake - Expected intake, this would mean 10 - 15 which is -5. Therefore, because actual is always less than expected you will always get a negative answer.

Hope this helps.

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JenLivYoung
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#1583
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#1583
(Original post by master y)
how are you reading around the subject? What sources are u using?
The BBC news health & science pages are useful, as they are current uses and often relate back to our course, but obviously extend it.
Some of the textbooks also are very helpful and include extra detail, so it's worth looking through them.
If a particular topic interests you then google it and see what articles and journals relate to it and read around it! It's always easier to learn things when you enjoy them
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loveheartsandall
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#1584
(Original post by lala12)
Well it might help if we add numbers to this. So say that the expected food intake is 15 arbitrary units. However, in reality, the animal only eats 10 arbitrary units. As RFI is Actual intake - Expected intake, this would mean 10 - 15 which is -5. Therefore, because actual is always less than expected you will always get a negative answer.

Hope this helps.

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That's perfect, thanks!!
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mariposaa
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#1585
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#1585
Hellooo everyone,

I just want to get an idea of what revision (if any) everyone is doing for the synoptic essay (and synoptic questions I guess), because I set myself the task of revising everything I think might be relevant, which as it turns out is pretty much the whole course... All that with Unit 5 added on plus extra bits for the high essay marks is proving a bit difficult to achieve.

What areas are you focusing on? Are you actively re-learning or just reading over the AS & Unit 4 textbook/notes?

Thank you!

Edit -- I haven't got any re-sits of previous units so I haven't looked at 1 and 2 since last year
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HopefulPharm
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#1586
Hi. I have a quick question. Any help will be much appreciated!!

From my (summarised) understanding of an action potential..

Stimulus > Na+ channels open and diffuse into axon - depolarisation
threshold - more Na+ channels open and even more Na+ ions diffuse in.
Action potential is reached.
Na+ channels close and K+ channels open - K+ ions leave axon
If too many K+ leave - hyper polarisation caused by overshoot
Heres where im slightly confused:
If K+ ions are leaving, why is it called REpolarisation?
When the membrane was polarised K+ ions moved IN making the axon more neg than outside. But not its the opposite?? So I dont understand how the resting potential is restored
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Smartass
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#1587
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#1587
Any idea on the essay question as to what jt could be


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erniiee
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#1588
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#1588
(Original post by HELPIMSTUCK)
SPECIFICATION A
Spoiler:
Show

- The importance of hydrogen bonds in living organisms

- How nitrogen-containing substances are made available to and are used by living organisms

- Carbon dioxide in organisms and ecosystems

- Why offspring produced by the same parents are different in appearance

- Describe how nitrogen-containing substances are taken into, and metabolised in, animals and plants.

-Inorganic ions include those of sodium, phosphorus and hydrogen. Describe how these and other inorganic ions are used in living organisms.

- Bacteria affect the lives of humans and other organisms in many ways. Apart from causing disease, describe how bacteria may affect the lives of humans and other organisms.

- Polymers have different structures. They also have different functions.Describe how the structures of different polymers are related to their functions.

- The structure and functions of carbohydrates

- Cycles in biology

- How carbon dioxide gets from a respiring cell to the lumen of an alveolus in the lungs

- How an amino acid gets from protein in a person’s food to becoming part of a human protein in that person

- Heat and many different substances are transferred within the human body and between the body and the environment. Explain how surface area is linked to this transfer.

- The transfer of energy between different organisms and between these organisms and their environment

- Ways in which different species of organisms differ from each other

- Negative feedback and its importance in biology

- Condensation and hydrolysis and their importance in biology

- Carbon dioxide in organisms and ecosystems

- Why offspring produced by the same parents are different in appearance

- The different ways in which organisms use ATP

- How the structure of cells is related to their function

- How bacteria affect human lives

- The biological importance of water



SPECIFICATION B
Spoiler:
Show


- The part played by the movement of substances across cell membranes in the
functioning of different organs and organ systems.

- The part played by enzymes in the functioning of different cells, tissues and organs.

- Movements inside cells.

- Transfers through ecosystems.

- The transfer of substances containing carbon between organisms and between organisms and the environment

- Cells are easy to distinguish by their shape. How are the shapes of cells related to their function?

- How microscopes have contributed to our understanding of living organisms

- Enzymes and their importance in plants and animals

- Negative feedback in living organisms

- Mean temperatures are rising in many parts of the world. The rising temperatures may
result in physiological and ecological effects on living organisms. Describe and explain
these effects.

- The biological importance of water.

- The movement of substances within living organisms.


- There may be more which I have not found. We did the specification A ones in college
Thank you so much!

(Original post by master y)
is IAA a hormone or a growth factor thingy?
IAA is plant growth factor. It can be considered the equivalent of a mammalian hormone. So it basically is a "plant hormone".
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samfreak
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#1589
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#1589
what could i write about in the negative feedback essay?

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Beth_L_G
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#1590
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#1590
(Original post by samfreak)
what could i write about in the negative feedback essay?

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Control of blood glucose, heart rate, menstrual cycle

That's not much, sorry. I can't think of many more examples :/
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master y
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#1591
(Original post by Beth_L_G)
Control of blood glucose, heart rate, menstrual cycle

That's not much, sorry. I can't think of many more examples :/

(Original post by samfreak)
what could i write about in the negative feedback essay?

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Is the predatoy-prey relationship one?
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JoshL123
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#1592
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#1592
Hi everyone. Just wondering, when we refer to Transcriptional factors, for this specification, are we to assume that they all function as activators or also as repressors. I came across a question n the june'10 paper of oestrogen. The description they provide in the mark scheme is of oestrogen functioning as an activator, though there are no clues in the question to suggest that all it functions is as an activator. Thank you!
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HopefulPharm
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#1593
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#1593
So no one can help me?
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pepeeglesfield
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#1594
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#1594
(Original post by HopefulPharm)
Hi. I have a quick question. Any help will be much appreciated!!

From my (summarised) understanding of an action potential..

Stimulus > Na+ channels open and diffuse into axon - depolarisation
threshold - more Na+ channels open and even more Na+ ions diffuse in.
Action potential is reached.
Na+ channels close and K+ channels open - K+ ions leave axon
If too many K+ leave - hyper polarisation caused by overshoot
Heres where im slightly confused:
If K+ ions are leaving, why is it called REpolarisation?
When the membrane was polarised K+ ions moved IN making the axon more neg than outside. But not its the opposite?? So I dont understand how the resting potential is restored
ok well well just so you know (incase you didn't already) both potassium and sodium are both positively charged. They call it positive and negative as it is all relative, due to sodium potassium pump, there is more sodium out than potassium in, so they call the inside negatively charged and out side positively charged.

ok, so, normally sodium are out but in the case of an action potential---membrane made permeable to sodium, hence there is an influx of sodium ions, along with the potassium ions ALREADY in there, so the charge of the Na and the K build up, past threshold, up to 40mV where then the K gates open, sodium close, so the sodium can't in effect escape, but the K can and by the process of diffusion they leave (from high conc to low conc) so this reduces the potential back down in to the minuses (but this is not normal for the axon membrane to have Na in and K out)----now, the K gates are slow to respond so they do not close in time hence there is a temporary overshoot.....once closed, its back down to the sodium potassium pump to restore normality in the axon, bringing back in the K from the outside and 'booting' out the Na ions which it doesn't want! thus resting potential is restored!
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pepeeglesfield
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(Original post by HopefulPharm)
So no one can help me?
I've responded, hope it helps ^^^^
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HopefulPharm
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#1596
(Original post by pepeeglesfield)
ok well well just so you know (incase you didn't already) both potassium and sodium are both positively charged. They call it positive and negative as it is all relative, due to sodium potassium pump, there is more sodium out than potassium in, so they call the inside negatively charged and out side positively charged.

ok, so, normally sodium are out but in the case of an action potential---membrane made permeable to sodium, hence there is an influx of sodium ions, along with the potassium ions ALREADY in there, so the charge of the Na and the K build up, past threshold, up to 40mV where then the K gates open, sodium close, so the sodium can't in effect escape, but the K can and by the process of diffusion they leave (from high conc to low conc) so this reduces the potential back down in to the minuses (but this is not normal for the axon membrane to have Na in and K out)----now, the K gates are slow to respond so they do not close in time hence there is a temporary overshoot.....once closed, its back down to the sodium potassium pump to restore normality in the axon, bringing back in the K from the outside and 'booting' out the Na ions which it doesn't want! thus resting potential is restored!
Thanks yeah I know its all relative.

I think I understand now. Thanks.
Only thing I wasnt really sure about is why the textbook seems to say its repolarised BEFORE the K+ ions move out. It never really mentioned the last bit that you did but I think it makes sense now
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HopefulPharm
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#1597
Oh its funny how me forgetting to read one little line made so so confused 'The gates on the potassium ion channels now close and the activities of the sodium-potassium pumps once again cause sodium ions to be pumped out and potassium ions in.' That would explain how its repolarised
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ahmmm
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#1598
did anyones college give them model answers for essays? :confused:
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mariposaa
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#1599
(Original post by JoshL123)
Hi everyone. Just wondering, when we refer to Transcriptional factors, for this specification, are we to assume that they all function as activators or also as repressors. I came across a question n the june'10 paper of oestrogen. The description they provide in the mark scheme is of oestrogen functioning as an activator, though there are no clues in the question to suggest that all it functions is as an activator. Thank you!
I would assume that when oestrogen acts as a transcriptional factor it is an activator because it activates transcription, rather than the other roles of oestrogen such as in the oestrous cycle where oestrogen acts as a hormone (and so not an activator per se). Not sure if I answered your question?
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starfish232
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#1600
Could someone please tell what topics i could discuss in the essay ' heat and many different substances are transferred within the body and beween the body and the environment. Explain how surface area is linked to this tranfer'

All I've got is:

The importance of sa:volume ratio is regards to transfer and reference to ficks law
Gas exchange of Insects and fish and humans
Photosynthesis (adaptation regarding surface area that increase photosynthesis)


Also can thermoregulation be included but since there's transfer of heat energy but i'm unsure as how to talk about surface area since i've just learnt about the process of thermoregulation
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