General ---------Biology----------------------------------------------------- ------------------Online-------------------------------------- Ch. 9 Cellular Respiration: Harvesting Chemical Energy

The pathway is illustrated in your text, Fig. 9.11, page 157.  Look at the pathway and answer the following questions.  Notice that the enzymes that catalyze each step are not listed as they were in glycolysis.  I assume the editors figured there was already a lot of information in the Figure. 

At what steps are carbon dioxide molecules given off? 3 & 4
How many ATP are produced? one
How many NADH* are produced? four
At what steps is NAD+ reduced to NADH? 3, 4, 8
At what step is ADP phosphorylated? 5
Write an input-output formula for Step 1. 

Acetyl CoA   +   Oxaloacetate

enzyme ? ---------------------------

Citate   +   CoA-SH

What does the enzyme at Step 2 do to Citrate to produce Isocitrate? Adds and removes a water molecule as rearranges the atoms.
At Step 4, how many carbons are in the substrate molecule, alpha-Ketoglutarate? 5
At Step 4, how many carbons are in the product molecule, Succinyl CoA? 4
What happened to the missing carbon? Released as carbon dioxide and ultimately exhaled
 

*Notice the FADH at step 6.  FADH is similar to NADH and serves a similar function.  For these questions, assume that FADH is NADH.

It is called a cycle because the starting substrate (oxaloacetate) is the same chemical as the final product.