Question

1) Discuss the role of NAD+ and FAD in cellular respiration.

2) give the balanced equation for the complete oxidation of one glucose molecule

3) Name 3 stages of cellular respiration. Outline where in the cell each stage occurs

4) In glycolysis, name the starting material, the end product, and the number of ATP and reduced NAD+ formed.

Answer 1

1) The NAD+ and FAD+ are the coenzymes play an essential role in the cellular respiration. During the glucose degradation by the glycolysis and Krebs cycle enzymes, NAD+ and FAD+ store the energy temporarily. The NAD+ and FAD+ are reduced to NADH2 and FADH2 during glucose degradation. The reduced NADH2 and FADH2 donate the electrons to the terminal oxygen by the four electron carriers of electron transport chain which create the proton gradient across the membrane. The proton gradient utilized for the generation of ATP by the ATP synthase complex.

2) Balanced equation for glucose oxidation in aerobic respiration

C6H12O6 + 6O2 → 6CO2 +6H2O + 36 ATP

3) Three stages of cellular respiration

Stage1: occurs in cytosol

Glycolysis: In the cytoplasm of a cell, the glucose is degraded by the glycolysis pathway. One glucose molecule (6 Carbon compound) enters into glycolysis produces two molecules of pyruvate (3 Carbon compound). During the degradation of glucose molecule produces two molecules of NADH and four ATPs but two ATPs are utilized for glycolysis process so the net gain is two ATPs at the end of glycolysis. Finally, only two ATP molecules are produced from degradation of one molecule of glucose by glycolysis pathway.

Stage2: occurs in Mitochondria

Formation of acetyl coenzyme A: The two private molecules produced in glycolysis do not directly enter into the Kreb’s cycle for further degradation. First, they are converted to acetyl coenzyme A by the enzyme called pyruvate dehydrogenase which is degraded by Krebs cycle enzymes. During this conversion, two NADH molecules are generated from two pyruvate molecules and two CO_2.

Stage3: occurs in Mitochondria

Krebs cycle: also called citric acid cycle or tricarboxylic acid cycle. The acetyl coenzyme A combine with one oxaloacetate molecule produces citrate. The citrate molecule degraded and oxaloacetate molecule is regenerated. During

The NADH2 generated in glycolysis & Krebs cycle enters into the electron transport chain oxidized into the NAD+.

Stage4: occurs in Mitochondria

Electron transport chain: it is located in the inner mitochondrial membrane with four protein complexes which carry electrons from the NADH2 and FADH2 to terminal oxygen and produces the NAD+ and ATP. Generation of ATP by the oxidation of NADH2 and FADH2 by electron transport chain is called oxidative phosphorylation. During the aerobic respiration total, 36 ATPs are produced.

4)

Starting material is Glucose and the end product is Pyruvate.

The number of ATP                = 2ATP

Reduced NAD+ formed         = 2 NADH2