An example of a hydrophobic group is the non-polar methane molecule.
This carboxyl group ionizes to release hydrogen ions (H+) from the COOH group resulting in the negatively charged COO- group; this contributes to the hydrophilic nature of whatever molecule it is found on.
Other functional groups, such as the carbonyl group, have a partially negatively charged oxygen atom that may form hydrogen bonds with water molecules, again making the molecule more hydrophilic.
Hydrogen bonds between functional groups (within the same molecule or between different molecules) are important to the function of many macromolecules and help them to fold properly and maintain the appropriate shape needed to function correctly.
Functional groups are groups of molecules that attached to carbon skeletons and give that molecule its specific identity or function.
Acetyl CoA is a molecule that is further converted to oxaloacetate, which enters the citric acid cycle (Krebs cycle).
A carboxyl group is removed from pyruvate, releasing a molecule of carbon dioxide into the surrounding medium.
This step proceeds twice for every molecule of glucose metabolized (remember: there are two pyruvate molecules produced at the end of glycolysis); thus, two of the six carbons will have been removed at the end of both of these steps.
The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl CoA.
This molecule of acetyl CoA is then further converted to be used in the next pathway of metabolism, the citric acid cycle.