The respiratory quotient, also known as the respiratory ratio (RQ), is defined as the volume of carbon dioxide released over the volume of oxygen absorbed during respiration.
Respiratory substrates are the organic nutrients oxidized at the time of respiration.
At the time of cellular respiration, oxidation of organic nutrients occurs to obtain energy (ATP). The order of preference of organic nutrients as respiratory substrates is – carbohydrates, lipid, and proteins.
Carbohydrates, lipids, proteins, and organic acids act as respiratory substrates.
So, yes organic acids are respiratory substrates.
Their R.Q. is more than 1.
The most common organic acids are carboxylic acids, lactic acid, etc.