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AQA BIOL4 ~ 11th June 2013 ~ A2 Biology

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Reply 820

master y

Original post by Starlight94

In the krebs cycle is it reduced NAD or just NAD that's produced? ahh last minture stress

reduced NAD

Reply 821

master y

Original post by stoppy123

Reduced NAD, they accept the hydrogens from the carbon compounds.

What would you say about conservation methods?

Reply 822

kdk

can someone explain question 7-e JAN 13 paper.
I don't get what ms says ; less effect on the environment ; concentrated due to evaporation; pesticide diluted in water;
How are the concentrations in the question related to these answers?? ( .001and 10 rather than .1 and 1.6 mg dm-3)
THanks :smile:

Reply 823

Starlight94

Original post by stoppy123

Reduced NAD, they accept the hydrogens from the carbon compounds.

Thanks, is it reduces FAD too?

Reply 824

Starlight94

Got a feeling we're going to get one of those pedigree charts, they're the worst things ever

Reply 825

Learner_108

Original post by kdk

I know they're not related, it's just one of the ways examiners make sure you don't get 75/75.

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Reply 826

stoppy123

Original post by Starlight94

Thanks, is it reduces FAD too?

Yup

Reply 827

hollywils

Original post by Starlight94

Got a feeling we're going to get one of those pedigree charts, they're the worst things ever

What is one of those?!?!?

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Reply 828

stoppy123

Original post by master y

What would you say about conservation methods?

Depends on what context. So for example:

"The government wants to protect Deep-sea bass as it is a vital part of a precious eco-system. State and explain how these deep-sea bass could be conserved"

You would say, you would put a fishing quote on these deep-sea bass, meaning that only a fixed amount of the deep-sea bass can be caught per year, so it leaves enough deep-sea bass in the sea for the eco-system to survive.

If the question was talking about a more severe case where an animal was endangered, you would say you could put it in captivity and rebuild it's numbers and then release them into the wild etc.

Reply 829

laser174572

Original post by hollywils

Please can you tell me some examples of conservation management?!?!?

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The example in the book is moorland and the red grouse and hen harriers on page 109/110, have a read through that. In general conservation techniques include controlled grazing, controlled burning of vegetation, removal of invasive species such as digging up trees and culling (not mentioned in the textbook but is a valid technique)

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Reply 830

stoppy123

Original post by hollywils

What is one of those?!?!?

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Reply 831

hollywils

Original post by stoppy123

Oh yeah! Thanks :smile:

Hope we don't get one of those.. They are awful

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Reply 832

Tikara

Original post by kdk

A lower concentration will have less effect on other organisms in the water
As it's a 16 day period the test is over, the concentration will go up due to evaporation (less water in the same volume)
The fourth point is referencing that they may need a more concentrate as the tadpoles are in water and it will get diluted when sprayed.

this question is annoying as it seems illogical, but remember it's all done in a controlled aquarium. The large range of concentrations is just to do with finding out the best concentration, and the first two marking points are for saying why such a low concentration may be useful and the third and fourth are saying how a high concentration may also be good.

I guarantee there will be a stupid question like this tomorrow -.- but thats aqa

(edited 10 years ago)

Reply 833

stoppy123

Original post by hollywils

Oh yeah! Thanks :smile:

Hope we don't get one of those.. They are awful

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It can be quite tricky to decipher them at times!

Reply 834

rac1

Really quickly can someone just describe bare minimum of Glycolysis, Link reaction, Krebs and ETC

PLEASE :smile:

Reply 835

kdk

anyone has end of the of unit 4 questions mark scheme?? thanks :smile:

Reply 836

kdk

Original post by kdk

anyone has end of the of unit 4 questions mark scheme?? thanks :smile:

Please

Reply 837

Tikara

Original post by kdk

anyone has end of the of unit 4 questions mark scheme?? thanks :smile:

http://www.thestudentroom.co.uk/showpost.php?p=42756888&postcount=64

Reply 838

HenriettaB

I have a really urgent question!

In the AQA Nelson Thornes book it says that in the Krebs cycle that citrate (the 6 carbon molecule) is recycled back into oxaloacetate (the 4 carbon molecule) by
1 ATP being formed by ADP + Pi (phosphorylation)
2 CO2
1 NAD reduced to reduced NAD
1 FAD reduced to reduced FAD

BUT in the AQA CGP textbook it says that there's a 5 carbon intermediate molecule (I don't think we have to know that) but that to recycle the citrate back to the oxaloaceate it by
1 ATP being formed by ADP + Pi (phosphorylation)
2 CO2
3 NAD reduced to reduced NAD
1 FAD reduced to reduced FAD

Is it 3NAD or 2NAD?! Help! Thanks (:

Reply 839

stoppy123

Original post by rac1

Really quickly can someone just describe bare minimum of Glycolysis, Link reaction, Krebs and ETC

PLEASE :smile:

Glycolysis

Glucose is phosphorylated by 2 ATP molecules, this makes 2x triose phosphate molecules, it is then converted into 2x pyruvate producing 4ATP and 2 Reduced NAD at the time.

Link reaction

Pyruvate is decarboxylated and is dehydrogenated to produce 1 co2 and 1 reduced NAD, the product of this (acetate) is then reacted with co-enzyme a to form acetyl coenzyme a.

Krebs cycle

The acetyl coenzyme A is reacted with a 4 carbon coumpound to produce a 6 carbon compound, this 6 carbon compound is then decarboxylated and dehydrogenated to produce a 5 carbon compound and 1 NADH and 1 CO2. This 5C compound is then dehydrogenated thrice and decarboxylated once and loses a phosphate group and then creates a 4 carbon compound which is then used at the start.

Altogether: 2 CO2, 1ATP, 3 NADH, 1 FADH.

Electron transport chain:

Hydrogen atoms are carried on reduced co-enzymes, these hydrogen atoms are then split into hydrogen ions and electrons. These electrons go along electron carriers and release energy at each carrier, this energy is then used to pump the hydrogen ions up a concentration gradient into the intermembrane space, this is continually done until the hydrogen ions fall down the gradient, via ATP synthase to create ATP, these hydrogen ions and electrons are then reacted with oxygen to create water.