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LegendX
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#701
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#701
AAnyone know why for question jan 2011 2bii, I can't say that because male 7 is rhesus negative so if the allele was present on the X chromosome it would get expressed therefore it cannot be on the X chromosome? Anyone?
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Nessie133
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#702
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(Original post by krane)
Which occurs in each stage? Is it substrate level for the first three and then oxidative phosphorylation in the electron transport chain on the membrane?
Substrate-level= glycolysis + krebs cycle

Oxidative= ETC

Photo=light-dependent reaction of photosynthesis
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Starlight94
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#703
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#703
I can never answer the anaerobic respiration questions?
What exactly do we have to know?
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SusieShire
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#704
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#704
So scared about this exam tomorrow. Desperately need a good A in this to get an A overall, got 72 UMS (B) last time. I've done all the past papers again, getting A*s each time like I did in January... So I'm just going to run through all my notes one last time and hope for the best. This exam is such a lottery when it comes to the mark scheme, I feel I must trust in good luck now. :crossedf:
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Tikara
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#705
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#705
(Original post by jonnyb123)
so what is the point in nitrification if the plants can make proteins with ammonia?

Okay slightly weird when I quote you it says something different...I was quoting this:

No, and the mark scheme is specific about this

nitrogen fixing bacteria convert nitrogen gas to ammonia, which is then used by the plant to make amino acids to make proteins.

(they aren't so picky about whether you say ammonium ions or ammonia though!)
yeah, I edited it because I slightly misunderstood what you said when I read your post again :P

But there I was talking about mutualistic nitrogen fixing bacteria, here the bacteria are directly fixed to the roots in nodules so the plants gain the ammonium ions and they are made into amino acids there and then in exchange for carbohydrates to the bacteria.

Plants can only uptake nitrates directly from the soil via active transport.

Also, not all plants are leguminous

(I actually think they can uptake ammonium ions also but prefer nitrates but AQA doesn't say anything about this so it's best to assume they can't)
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hollywils
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#706
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#706
Can anyone please tell me the advantages and disadvantages of using inorganic artificial fertiliser?!


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krane
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#707
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#707
(Original post by Nessie133)
Substrate-level= glycolysis + krebs cycle

Oxidative= ETC

Photo=light-dependent reaction of photosynthesis
Thanks, but why exactly is ETC oxidative? Because doesn't it involve direct linking of ADP and phosphate ion from energy released when electrons move down the chain? I've never understood this.
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Starlight94
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#708
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#708
Ideal paper:

Hardy weinburg
Mark, release, recapture
Eutrophocation
Photosynthesis
Aerobic Respiration
Carbon cycle and nitrogen cycle I find confusing, always forget the points but would be okay if it came up

No:
Succession (so hard to word the answers)
Directional/stabilising selection (again, hard to word)
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Scienceisgood
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#709
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I just hope nothing on anaerobic respiration comes up tomorrow.
The one thing I don't know. =(
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krane
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(Original post by SusieShire)
So scared about this exam tomorrow. Desperately need a good A in this to get an A overall, got 72 UMS (B) last time. I've done all the past papers again, getting A*s each time like I did in January... So I'm just going to run through all my notes one last time and hope for the best. This exam is such a lottery when it comes to the mark scheme, I feel I must trust in good luck now. :crossedf:
Same! I got 72 and could do with highering it so I don't have to get as much in unit 5 to get an A :/ didn't help that the grade boundaries were so close together in January, 4 more marks and it would have been an A :mad:
Feel like I've neglected this one though, was focusing on maths this morning, done nowhere near as much as I did in January so can't see how I can do any better!
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flyylikejetz
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(Original post by LegendX)
AAnyone know why for question jan 2011 2bii, I can't say that because male 7 is rhesus negative so if the allele was present on the X chromosome it would get expressed therefore it cannot be on the X chromosome? Anyone?
Its more about where the male gets the allele on the X chromosome from
Males only get it from their mothers, so if you have 2 a mother who is homozygous recessive, if it was carried on the X chromosome the male would express the recessive allele but 3 is rhesus positive and doesn't express this thus it can't be on the x chromosome
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rommy123
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#712
(Original post by Scienceisgood)
I just hope nothing on anaerobic respiration comes up tomorrow.
The one thing I don't know. =(
mee too!!
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krane
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(Original post by Scienceisgood)
I just hope nothing on anaerobic respiration comes up tomorrow.
The one thing I don't know. =(
There's not much on it we need to know is there? Just that only glycolysis can occur, so 2ATP from here.
Plants - Pyruvate (lose CO2) > ethanal (NADH-NAD) > ethanol
Animals - pyruvate (NADH to NAD) > lactate - removed by blood to liver, converted to glycogen when oxygen available, causes cramp if it accumulates.

What else do we need to know?
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ActaNonVerba
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#714
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#714
Why does question 7 even exist .. just did jan 2013 got 50 today (got 49 in January) and got 3/15 on question 7.. Any tips on tackling question 7?
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cheesypuff
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#715
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#715
Do we need to know about photosystems and how they work??
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Tikara
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#716
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#716
(Original post by cheesypuff)
Do we need to know about photosystems and how they work??
no we don't - they just accept chlorophyll absorbs light energy, to excite electrons etc.
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billybobs
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#717
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(Original post by cheesypuff)
Do we need to know about photosystems and how they work??
No
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Scienceisgood
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#718
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#718
Question guys;

After going through June 2012 paper, it says no NADPH produced during electron transport chain, I thought NAD was reduced, not NADP?

Name:  Question.PNG
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EDIT:
Said Jan 13 by mistake.
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Scienceisgood
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(Original post by cheesypuff)
Do we need to know about photosystems and how they work??
Maybe for the unit 5 essay (for an extra couple of marks for things outside the spec)
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jennyruneckles
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#720
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#720
HELP!!! I have been doing the june 11 past paper and don't understand why the answer would be 4?


6 Sea otters were close to extinction at the start of the 20th century. Following a ban
on hunting sea otters, the sizes of their populations began to increase. Scientists
studied the frequencies of two alleles of a gene in one population of sea otters.
The dominant allele, T, codes for an enzyme. The other allele, t, is recessive and
does not produce a functional enzyme.
In a population of sea otters, the allele frequency for the recessive allele, t, was found
to be 0.2.
6 (a) (i) Use the Hardy-Weinberg equation to calculate the percentage of homozygous
recessive sea otters in this population. Show your working.
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