Question

which is a difference between proteins and carbohydrates and fats?
proteins are macromolecules; carbohydrates and fats are not.
proteins are composed of monomers; carbohydrates and fats are not.
carbohydrates and fats contain carbon, hydrogen, and oxygen; proteins do not.
excess carbohydrates and fats are stored; excess proteins are not.

Explanation:

• All three (proteins, carbohydrates, fats) are macromolecules composed of monomers. Proteins have amino - acid monomers, carbohydrates have monosaccharide monomers, and fats have glycerol and fatty - acid "monomers" (though fats are not true polymers like proteins and polysaccharides).
• Proteins do contain carbon, hydrogen, and oxygen (in addition to nitrogen and sometimes sulfur).
• Excess carbohydrates are stored as glycogen (in animals) or starch (in plants), excess fats are stored in adipose tissue. But excess proteins are not stored as protein. The body breaks down excess amino - acids (from proteins) through deamination, and the nitrogen is excreted (e.g., as urea in humans), and the carbon - containing skeletons can be used for energy production or converted to carbohydrates or fats.

Answer:

Excess carbohydrates and fats are stored; excess proteins are not.