You asked part 1

Since Charlotte asked about the proton pumps, I thought I’d go into a bit more detail.

The pumps are referred to as complexes, given Roman numerals I, II, III and IV. Complex I is really an enzyme, called NADH dehydrogenase (why is it called a complex? There are 45 separate polypetide chains). 2 electrons are passed onto a substance called ubiquinone (or just Q), which is reduced to ubiquinol (QH2). This is lipid soluble, and moves easily through the membrane. 4 protons are pumped through the membrane.

Complex II (aka succinate dehydrogenase)  gives additional electrons to Q, which is then passed to Complex III (aka cytochrome bc complex). Here the electrons are passed on to another molecule, cytochrome C. 6 protons in total are translocated (moved across the membrane) at this point. Finally cytochrome C (whgich is a water soluble, integral protein membrane) electrons on to Complex IV, where the electrons are removed and used in reducing oxygen to water. Cytochrome C is inhibited by cyanide – a poison which will stop aerobic respiration.

Here’s a nice summary from wikipedia:

In eukaryotes, NADH is the most important electron donor. The associated electron transport chain is

NADHComplex IQComplex IIIcytochrome cComplex IVO2 where Complexes I, III and IV are proton pumps, while Q and cytochrome c are mobile electron carriers. The electron acceptor is molecular oxygen.

Remember, you will be tested on what is in the specification, but reading further in your subject will always help.


If you want to get ahead, read a book.

If you are interested in science (and since you are doing at least one A level in science, I presume you are), then you really need to start looking beyond what you have to do as a part of the course and read around your subject. This doesn’t have to mean looking at textbooks; popular science books are very good at informing and entertaining. There is also a rich tradition of fiction that has its roots in science (you think it’s an accident that physicists all like Star Trek?). While TV and fiction cannot replace understanding and knowledge when it comes to exams, get reading over the summer. Ask for a book for Christmas (yes, it is legal, you’re allowed!). Visit the LRC, the you’ll find many of these books there for free. Apart from the possibility of being asked about your wider understanding of a subject in a university interview, it’s worth it to broaden your mind.

Some suggestions:
A Short History of Nearly Everything, Bill Bryson

An entertaining guide to most of the big ideas of science; biology, chemistry and physics. Gives the background to discoveries, including some interesting biographical information of scientists.

The Selfish Gene, Richard Dawkins

Getting old now, this book is still a classic in how it introduced genetic ideas to a wider audience. Dawkins’ other books are worth a look, such as Climbing Mount Improbable and  The Greatest Show on Earth.

Genome, Matt Ridley

Looks at the human genome through the idea of looking at one gene per chromosome. A good outline of this exciting area of biology. Some other good stuff by Matt Ridley as well.

Power, sex, suicide:mitochondria and the meaning of life, Nick Lane

You know you want to read a book with a title like that.

Not clear?

Keep it simple people…

Despite what you may think, the stuff we’ve covered so far in respiration is actually pretty straightforward. Just as we found out that our original formula for respiration (glucose + oxygen…) is hiding a wealth of sub-reactions that aren’t shown, the simple pathways of glycolysis and Krebs cycle have many steps that don’t need to concern us. If you want to look at them in more depth then fire away. Anyone considering following a biochemical course may wish to poke around further.

It is one of the areas of A2 that can be remembered by rote, however we have spent time trying to get an overview that will make understanding it a lot easier. Even so, you will forget most of this over the summer break, so anything you are not sure on now is the time to find out.

A few links that may be of help.

Cellular respiration flash

Glycolysis animation

The Student Room questions on glycolysis

Animation Krebs cycle

Another Krebs cycle

Youtube is also pretty good for videos, have a look if you can spare the time between looking at clips of dogs falling over and things that are ‘the funniest thing EVER’, which of course, they never are.