Final answer:
Carbohydrates are converted into glucose approximately 1-2 hours after a meal. Proteins are unable to be converted into glucose.
Step-by-step explanation:
The approximate time period for the conversion of carbohydrates into glucose after a meal can vary depending on the individual and the specific meal. However, generally, it takes about 1-2 hours for carbohydrates to be converted into glucose and enter the bloodstream.
Regarding the second question, the macromolecule that is unable to be converted into glucose by the human body is proteins. Proteins are broken down into amino acids during digestion, which are used for various functions in the body, but they cannot be converted into glucose.