Question

Given the conversion factor that 7.3 kcals are required to produce 1 mole of ATP. How many moles of ATP would be created in the human body with the metabolism of 1 mole of glucose?

32

686

94

73

Answer 1

Ans 32

Cellular respiration can be broken down into 5 steps, and all of them - except for the first one - occur inside mitochondria.

1. Glycolysis
Converts 1 molecule of glucose into 2 molecules of pyruate.

Glycolysis consists of two phases: the energy investment phase (consumes 2 ATP to get things started) and the energy capture (or energy recovery) phase (produces 4 ATP). Consuming 2 and producing 4 means there are 2 net ATP produced.

In the process, glycolysis reduces 2 NAD+ to 2 NADH.

Main products: 2 pyruvates, 2 net ATP, and 2 NADH.

2. Link reaction
Converts the 2 pyruvates into 2 acetyl CoA.

Main products: 2 acetyl CoA and 2 NADH

3. Citric acid cycle

For each turn (2 turns per staring glucose), combines a 4-carbon molecule called oxaloacetate with a 2-carbon acetyl group from acetyl CoA to produce the 6-carbon molecule citrate (which is just citric acid, with acidic protons removed). In further processes, the oxaloacetate is reformed, ready to accept another acetyl group to begin a new turn of the cycle.

Per turn, the citric acid cycle produces 3 NADH and 1 FADH2 (and releases 2 CO2, which arose from decarboxylations). Since the cycle turns twice per starting glucose, the final output is

Main products: 6 NADH and 2 FADH2 +2 ATP/GTP(and 4 CO2 released)

4. Electron transport
Uses energy from electrons donated by NADH and FADH2 to produce an electrochemical gradient across the inner mitochondrial membrane.

In previous steps, per starting glucose, 10 NADH and 2 FADH2 were produced. These donate their electrons to the electron transport chain.

high-energy electrons are passed between the respiratory complexes of the respiratory chain in the membrane until they are received by the terminal electron acceptor, oxygen; this forms water.

Since oxygen is the electron transport chain’s terminal electron acceptor, it is aerobic respiration that occurs in mitochondria.

5. Chemiosmosis
Uses the PMF (proton motive force) of the electrochemical gradient to produce about 28 ATP.

Main products: About 28 ATP

The last two steps can be combined into a process called oxidative phosphorylation.

New estimates: 2.5 ATP / NADH and 1.5 ATP / FADH2, gives 28 ATP
(10 NADH )* (2.5 ATP / NADH) = 25 ATP
(2 FADH2) * (1.5 ATP / FADH2) = 3 ATP

Adding those 28 ATP with the 2 net ATP produced in glycolysis and the 2 ATP produced in the citric acid cycle, results in a grand total of about 32 ATP per glucose.