Question

At the start of the year, a team of people decides to start a weight-loss journey. They decided to eat mostly high-protein, low-carbohydrate foods such as meat, cheese, and eggs. The amino acids in these protein-rich diets, such as alanine, glycine, and serine, can be converted to pyruvate by deamination (removal of the amino group). Using your knowledge of cellular respiration, how many ATP, NADH, and FADH2 molecules will be generated from one molecule of alanine during the reactions of pyruvate oxidation and the citric acid cycle?

Answer 1

After deamination of alanine the two molecules of pyruvate is released, which contains lots of energy. Before going into cytric acid cycle, the pyruvate molecules undergo modification by removal of carboxyl group for the attachment with coenzyme A (CoA). This process of attachment is known as pyruvate oxidation.

  

COA-SH CO. 000 to Pyruvate NAD NADH 00-COA Acetyl coa

Step 1: The presence of carboxyl group is cut off from the pyruvate and this cutoff is released as Co2 molecule. The process leaves two molecules of carbon.

Step 2: The availability of two carbon molecule in step 1 is then oxidized. During this, a electron which are lost are used up by NAD +. This NAD+ with electron forms NADH.

Step 3: The two carbon molecule which was oxidized is acetyl group. This acetyl group is attached with CoA (Coenzyme A). THis CoA is an organic one which is formed from B5 vitamin. The attachment of acetyl group with CoA forms acetyl CoA, which is also known as carrier molecule. The name carrier molecule because it carry or transfer acetyl group to "citric acid cycle".

At the end of pyruvate oxidation process the two NADH are generated from NAD+.

Cytric Acid Cycle: It is also known as krab cycle and carboxylic cycle.

Acetyl CoA oo-CoA Six-carbon molecule formed from acetyl COA + oxaloacetate O 0000 Citrate Four-carbon acceptor molecule (regenerated in each cycle) 3oooo Oxaloacetate One carbon lost as со NAD+ NADHK NADHI + NAD+ ooooo 1 NADT second carbon lost as Coz 0060 Reduced electron carrier similar to NADH AD FAD G GDP, 2 Energy - carrying 2 molecule equivalent to ATP

If one acetyl CoA molecule undergo one turn of cytric acid cycle then the number of molecules are as follows:

• 3 molecules of NADH
• 1 molecule of FADH2
• 1 molecule of ATP or GTP

But during the deamination of alanine the two molecule of pyruvate is formed. These two pyruvate molecules undergo pyruvate oxidation process and form 2 molecule of acetyl CoA. So one molecule of Acetyl CoA form 3 molecule of NADH, 1 molecule of FADH2 and 1 molecule of ATP by the single turn of cytric acid. Moreover, If the cycle repeats again then the amount of molecules will be increases by double. Means there will be 6 molecules of NADH, 2 moleccules of FADH and molecules of ATP.