Respiratory substrate yielding maximum number of ATP molecules is glucose. One glucose molecule on aerobic respiration yields 36 ATP molecules.

Respiratory substrate yielding maximum number of ATP molecule is glucose.

Explanation:
Glucose is the preferred respiratory substrate for most cells in the body. It undergoes a series of metabolic reactions within the cell to produce ATP, the energy currency of the cell. The process by which glucose is oxidized to produce ATP is called cellular respiration.

Steps of glucose metabolism:
1. Glycolysis: Glucose is broken down into two molecules of pyruvate in the cytoplasm. This process produces a small amount of ATP and NADH.

2. Pyruvate Decarboxylation: Pyruvate is transported into the mitochondria and converted to Acetyl-CoA. This step generates NADH.

3. Krebs Cycle: Acetyl-CoA enters the Krebs cycle, a series of enzymatic reactions that occur in the mitochondria. During the cycle, Acetyl-CoA is completely oxidized, generating NADH, FADH2, and ATP.

4. Electron Transport Chain (ETC): NADH and FADH2 generated in the previous steps donate their electrons to the ETC, located in the inner mitochondrial membrane. This transfer of electrons produces a proton gradient, which drives ATP synthesis by ATP synthase. This process is known as oxidative phosphorylation.

ATP yield:
The complete oxidation of one glucose molecule through cellular respiration can produce a maximum of 38 ATP molecules. This includes 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and approximately 34 ATP from oxidative phosphorylation.

Comparison with other substrates:
- Ketogenic amino acids: These amino acids can be converted to Acetyl-CoA, but they do not directly enter the Krebs cycle. Therefore, their ATP yield is lower compared to glucose.
- Amylose: Amylose is a form of starch. It is broken down into glucose molecules during digestion, and then the glucose follows the same metabolic pathways as described above.
- Glycogen: Glycogen is the storage form of glucose in animals. It is broken down into glucose molecules when energy is needed. Once again, the glucose follows the same metabolic pathways as described above.

Therefore, glucose is the respiratory substrate that yields the maximum number of ATP molecules because it can undergo complete oxidation through glycolysis, the Krebs cycle, and oxidative phosphorylation.