The breakdown of carbohydrates into glucose. Glucose use to obtain energy (ATP) for the human cellular respiration by the steps glycolysis, acetyl CoA and kreb cycle. In glycolysis, ATP is use to generate greater ATP called the ATP debt. Fat (lipid) and protein (amino acid) also can give human energy call gluconeogenesis but only when critical condition only.
Yes, it is a weak acid called the citric acid
Bones teeth and maybe scull
I think It Would Be Monday Be It's The Day Before Tuesday