A different approach to teaching (aerobic) respiration - A-level Biology

Teaching aerobic respiration is a difficult topic, traditionally,  teachers begin with glycolysis, then link reaction and krebs cycle and then the electron transport chain, I would argue that there is a better way to teach this.

I begin by teaching the structure of adenosine triphosphate, the need for ATP, and the concept of ATP as a currency that connects the source of the energy (which is the food) to where the energy currency is being consumed, in specific processes such as protein synthesis, DNA synthesis and the movement of ions against a concentration gradient.

I focus on the transient nature of the ATP and the disparity between the 5g in the body compared the 80kg turned over per day.

Then discuss the processes which are used to produce the ATP - substrate level phosphorylation and chemiosmosis.

After an explanation of chemiosmosis, I then lead on to the flow of electrons through the electron transport chain (and therefore the creation of the proton gradient between inter membrane space and matrix) which focuses on the electron on the last carrier and that it has to be accepted by oxygen to produce water.

Then you look at where the electron has come from.  

I start with the production of the electron from the breakdown of pyruvate to acetyl and the acceptance of the electron by NAD, (at the same time pyruvate is decarboxylated).  I repeatedly emphasize regeneration of NAD when the electron is passed from NADH to the electron transport chain.

Then you move on to the krebs cycle.

When teaching the Krebs cycle initially focus on the number of carbons and the decarboxylation and the dehydrogenation avoid discussions of the names of the intermediates and just keep the students focused on the big picture, which is the production of a reduced carriers (NAD and FAD).

Use the production of ATP/GTP directly in krebs cycle as an opportunity to recap about substrate level phosphorylation (with an eye on teaching glycolysis later)

Always keep emphasizing the fate of the reduced carriers that the electrons end up on the electron transport chain and then ultimately joining with oxygen to produce water (and this regenerates the electron carriers)

After teaching Link reaction and Krebs cycle, discuss other potential respiratory substrates - amino acids and fats - and where they might enter the Krebs cycle and Link reaction.

Finally look at glycolysis,  emphasise that only glucose enters glycolysis and that the products do not include carbon dioxide and that oxygen is not consumed.

 Emphasize the production of reduced NAD and then use that as a point to discuss as to how the NAD could be regenerated in the absence of oxygen and emphasize that anaerobic respiration is just glycolysis with an alternate way of getting rid of the reduced NAD.

Give it a go and see how you get on !