In a eukaryotic cell, the process of cellular respiration can metabolize one molecule of glucose into 30 to 32 ATP. The process of glycolysis only produces two ATP, while all the rest are produced during the electron transport chain.

30 moles of ATP are produced from 1 mole of glucose through the Krebs cycle.

2 mol

In eukaryotic cells, the theoretical maximum yield of ATP generated per glucose is 36 to 38, depending on how the 2 NADH generated in the cytoplasm during glycolysis enter the mitochondria and whether the resulting yield is 2 or 3 ATP per NADH.

The total quantity of ATP in the human body is about 0.2 moles. The majority of ATP is recycled from ADP by the aforementioned processes. Thus, at any given time, the total amount of ATP + ADP remains fairly constant.

Web Link. 2.5 ATP/NADH and 1.5 ATP/FADH2 are produced in the electron transport chain. Some resources will say 3 ATP/NADH and 2 ATP/FADH2, but these values are generally less accepted now.

Why do eukaryotes generate only about 36 ATP per glucose in aerobic respiration but prokaryotes may generate about 38 ATP? A) eukaryotes have a less efficient electron transport system. eukaryotes do not transport as much hydrogen across the mitochondrial membrane as prokaryotes do across the cytoplasmic membrane.

Why is the total count about 36 or 38 ATP molecules rather than a specific number? Since phosphorylation and the redox reactions aren’t directly coupled to each other, the ratio of the number of NADH molecules to the number of ATP molecules is not a whole number.

According to some newer sources, the ATP yield during aerobic respiration is not 36–38, but only about 30–32 ATP molecules / 1 molecule of glucose, because: ATP : NADH+H+ and ATP : FADH2 ratios during the oxidative phosphorylation appear to be not 3 and 2, but 2.5 and 1.5 respectively.

The three stages of aerobic cellular respiration are glycolysis (an anaerobic process), the Krebs cycle, and oxidative phosphorylation….Aerobic vs anaerobic respiration.

There are two main types of anaerobic respiration, alcoholic fermentation and lactic acid fermentation.

2 molecules

Higher respiration rate is seen in floral vegetative bud, germinating seedlings, young leaves, etc.

In anaerobic respiration, oxygen is not consumed and carbon dioxide is released. This gives the RQ quotient to be infinite. This is explained by the equation RQ= CO2 divided by O2 = 20 = Infinity.

2 ATP

Respiratory quotients of some substances

Malic acid :- 1.4 is the RQ value of the malic acid that is an organic acid . The RQ value of organic acid is usually more than the unity because organic acids contain high amounts of oxygen and low amounts of carbon and hydrogen .

C2H2O4

Fats and proteins contain a smaller number of oxygen atoms than carbon atoms in their molecules. When fats are used as a substrate in respiration, the RQ is less than 1 because the amount of oxygen utilised is always higher than the amount of carbon dioxide released.

At the state of rest the RER, completely known as the respiratory exchange ratio, is actually the same as RQ or respiratory quotient. The RQ is a metabolic exchange of gas ratio that is equal to CO2 production over oxygen uptake (CO2/O2).

Respiratory quotient (RQ) or respiratory ratio can be defined as the ratio of the volume of CO2 evolved to the volume of O2 consumed during respiration. However, it is always less than one for fats as fats consume more oxygen for respiration than carbohydrates.

An RER near 0.7 indicates that fat is the predominant fuel source, a value of 1.0 is indicative of carbohydrate being the predominant fuel source, and a value between 0.7 and 1.0 suggests a mix of both fat and carbohydrate. …

As the intensity of the exercise increases and carbohydrates become the dominant or primary fuel, the respiratory quotient and the RER increase to between 0.9 and 1.0. Because RER reproducibly increases during exercise, it is considered a parameter that can document maximal effort.

The major determinants of resting RER included muscle glycogen content, training volume, proportion of type 1 fibers, [FFA] and [lactate], and %dietary fat intake (adjusted r(2) = 0.59, P < 0.001). Except for muscle fiber composition, these variables also predicted RER at 25, 50, and 70% W(peak) to different extents.

Respiratory Exchange Ratio

A maximal exercise respiratory exchange ratio (RERmax) ≥1.10 is commonly used as a criterion to determine if a “true” maximal oxygen uptake (VO2max) has been attained during maximal-effort exercise testing.