A Cycle Known as TCA
(To the tune of "God Rest Ye Merry Gentlemen")
Copyright 2008 Tari Tan

Our fats and carbs get broken down
To acetyl CoA
Oxaloacetate combines
In cycles TCA

The product of reaction one
Oh, citrate is its name

Iso-citrate, the product that ensues
Atoms got moved
Isocitrate is the product of step two

An oxidation soon occurs
Reducing NAD
An alpha-ketoglutarate
Resulting from step three

From here we could make glutamate
That is, if there’s a need

Don’t forget that we lost a CO₂
Yes it is true
In reaction three we lost a CO₂

So what’s the point of all these steps?
Well, let me tell you, friend
We use electron carriers
In working towards our end

Of synthesizing ATP
(A metabolic trend)

Oxidize, and then oxidize some more
Here in step four
Ketoglutarate gets oxidized some more

The enzyme with cofactors five
Including TPP
Lipoate, FAD, CoA
And also NAD

A succinyl that’s on CoA
Is what gets made, you see

This reaction occurs so fav’rably
Don’t you agree?
It’s a good reaction energetically

With four more steps, we’re halfway there
So let me summarize
When CoA’s lost we see that G-
T-P is synthesized

The succinate that is produced
Will soon get oxidized

FAD goes to FADH₂
What did we do?
We made fumarate and FADH₂

Add water ‘cross the double bond
And malate we create
With one last NAD we can
Then dehydrogenate

To give a final product of
Oxaloacetate

It’s removed, and this lowers Delta G
Oh yes, indeed
It’s through pulling that this last step can proceed

MORE