Edexcel A2 Biology SNAB 6BI04 ~ 6BIO5 June 2016

For glycolysis you're producing two reduced NAD because there are two 3 carbon molecules.

in my notes from class NAD gets reduced to produce NADH + H+ in the krebs cycle and in the CGP text book during oxidative phosphorylation reduced NAD releases 2 hydrogen atoms to produce two electrons.

Not sure if this helped whatsoever cause i'm starting to confuse myself but if you look in the CGP textbook for the oxid. phos. you can see reduced NAD releases two hydrogen atoms

Hi, 2 hydrogens reduce one NAD and 1 H20 molecule will be made from 1 NADH (as it releases to 2 H).

Hope that helps.

I had a question about redox reactions. In the book it says that reduction occurs when electrons or hydrogen atoms are added, or when oxygen is removed. Why does removing oxygen cause reduction?

Oxidation is the loss of electrons OR adding oxygen so, reduction happens when oxygen is removed

Also, for the structure of a mitochondrion, how should I draw the outer membrane? I've seen it drawn different ways on the internet. I've attached two images and I'm never sure which is the right drawing.

First one - definitely .... there are only 2 membranes in the mitochondrion. Outer membrane is single membrane and inner membrane is the one that is folded into cristae. Have seen this commented in Examiner's report

It says that in the book as well, but I get confused with oxygen and its role in redox reactions. I know that oxidation is the loss of electrons. But oxygen has electrons too so when oxygen is added, don't electrons get added too? So if those electrons are added, why is it still described as oxidation, which should be the loss of electrons?

I know the book says oxidation occurs when oxygen is added and I accept that because I've seen it in other places as well. I just want to understand why adding oxygen is described as oxidation, and removing oxygen is described as reduction.

I'm sorry if it's a really stupid question. I just can't get my head around it.

Reduction and oxidation are defined in different ways. It can be in terms of oxygen, hydrogen and electron transfer.
-When a compound gains oxygen it is oxidised, when it looses oxygen it is reduced
-When a compound gains hydrogen it is reduced, when it looses hydrogen it is oxidised.
-When a compound gains electrons it is reduced,when it looses electrons it is oxidised.
When a compound gains oxygen, it is oxidised because it is referring to the first definition, (eventhough oxygen has electrons the overall oxidation state of the compound will become more positive as the whole compound will loose more electrons then it will gain). This is getting more into the chemistry side of things tho.
Hope this helps

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Do we need to learn about the enzymes involved in glycolysis? I know there's phosphofructokinase do we need to learn the others.

Can someone send me a link to the pre release please ?