Upon oxidation of 1 molecule of pyruvic acid in mitochondrial respiration the mole-cules of ATP generated are

Options

A. 38
B. 30
C. 8
D. 15

Answer

To determine the number of ATP molecules generated from the oxidation of one molecule of pyruvic acid during mitochondrial respiration, we can follow these steps:

### Step 1: Understand Glycolysis
- Glycolysis is the first step in cellular respiration, where one molecule of glucose (which is broken down into two molecules of pyruvic acid) generates:
- 2 ATP (net gain)
- 2 NADH

**Hint:** Remember that glycolysis occurs in the cytoplasm and produces pyruvate along with ATP and NADH.

### Step 2: Oxidative Decarboxylation
- Each pyruvic acid molecule undergoes oxidative decarboxylation to form acetyl CoA. This process also produces:
- 1 NADH per pyruvic acid molecule.

**Hint:** Focus on the conversion of pyruvic acid to acetyl CoA and the production of NADH during this step.

### Step 3: Krebs Cycle (Citric Acid Cycle)
- Each acetyl CoA enters the Krebs cycle. For each turn of the Krebs cycle (which processes one acetyl CoA), the following is produced:
- 1 ATP
- 3 NADH
- 1 FADH2

Since one glucose molecule produces two pyruvic acid molecules, the Krebs cycle will turn twice (once for each acetyl CoA):
- Therefore, from two acetyl CoA, we get:
- 2 ATP
- 6 NADH
- 2 FADH2

**Hint:** Remember that each glucose molecule leads to two cycles of the Krebs cycle due to the two pyruvate molecules produced.

### Step 4: Calculate ATP from NADH and FADH2
- Each NADH can generate approximately 3 ATP, and each FADH2 can generate approximately 2 ATP during oxidative phosphorylation:
- From 6 NADH: 6 x 3 = 18 ATP
- From 2 FADH2: 2 x 2 = 4 ATP

**Hint:** Use the conversion rates of NADH and FADH2 to ATP to calculate total ATP yield.

### Step 5: Total ATP Calculation
- Now, we can sum up all the ATP produced:
- From glycolysis: 2 ATP
- From oxidative decarboxylation: 1 NADH = 3 ATP
- From Krebs cycle: 2 ATP + 18 ATP (from NADH) + 4 ATP (from FADH2) = 24 ATP

Total ATP from one glucose molecule (which produces two pyruvic acid molecules):
- 2 (from glycolysis) + 3 (from oxidative decarboxylation) + 24 (from Krebs cycle) = 29 ATP

Since we are calculating for one molecule of pyruvic acid:
- Total ATP = 29 ATP / 2 = 14.5 ATP, which is typically rounded to 15 ATP.

### Final Answer
Thus, the total number of ATP molecules generated upon oxidation of one molecule of pyruvic acid in mitochondrial respiration is **15 ATP**.