What must be removed from an amino acid before its carbon skeleton can enter the pathways of glucose catabolism?

1. Excess amino acids, or amino acids released in starvation, are shunted into glucose catabolism. 2. Each amino acid must have its amino group removed prior to entry. 3. That amino group is converted into ammonia. 4. Amino acids carry no phosphate group to remove, so that option is impossible from the outset. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.6 Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways_