Describe a receptor molecule ​

receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems

Explanation:

a protein which binds to a specific molecule. The molecule it binds is known as the ligand. A ligand may be any molecule, from inorganic minerals to organism-created proteins, hormones, and neurotransmitters.

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.

c.           is the correct answer