Log In | Register

Key Idea: To build body structures, multicellular organisms use monomers (e.g., amino acids, glucose) to make polymers (e.g., proteins, carbohydrate polymers) that make up their body structures. An input of energy is required for these chemical reactions to occur.

Students are expected to know that:

  1. To build body structures for growth and repair, plants use glucose monomers to make carbohydrate polymers and water molecules. Carbohydrate polymers can also be stored in seeds for their offspring.
  2. Plants and some other organisms can use glucose molecules and a source of nitrogen atoms to make amino acids monomers.
  3. Plants can use the amino acids monomers to build protein polymers that can be used immediately or stored (in seeds) for their offspring.
  4. Organisms that eat plants can use carbohydrate and protein polymers as a source of glucose and amino acid monomers needed to build their body structures.
  5. The large carbon-based molecules (polymers) that make up animal body structures are made up of the same types of small carbon-based molecules (monomers) as the food an animal eats but differ in the specific monomer composition and arrangement. Hence, they are different molecules.
  6. These molecules, mainly protein, carbohydrate, and fat polymers, are broken down in the digestive system into smaller carbon-based molecules (monomers) such as amino acids, glucose, and fatty acids, during chemical reactions with water molecules.
  7. Within body cells, the monomers can react with one another to form polymer molecules that become part of the animal’s body. Water molecules are also produced during polymer formation.
  8. When organisms grow or repair, they increase in mass. Atoms are conserved when organisms grow: The increase in measured mass comes from the incorporation of atoms from molecules that were originally outside of the organism’s body.
  9. Energy is required to form proteins and water from amino acids.
  10. Energy is required to form carbohydrate polymers and water from glucose molecules.


  1. Students are not expected to know that protein digestion does not release sufficient energy for ATP synthesis and that the energy released during digestion is all transferred to the surroundings as heat.
  2. Students are not expected to know that protein synthesis requires much more energy than is released during protein digestion or that the reason is because cells need to correctly sequence the amino acids, which requires synthesis and maintenance of ribosomes.
Frequency of selecting a misconception

ID Number

Student Misconception

Pre-Test Post-Test


Food is turned into energy and is used up in the process (Smith & Anderson, 1986).




Organisms grow by cell division, but the cells do not themselves increase in size or mass (AAAS Project 2061, n.d.).




Energy can be changed into matter or atoms.




The carbohydrates, fats, and proteins from the food people eat are used by the body unchanged; they are not broken down into smaller molecules (AAAS Project 2061, n.d.).




Food is simply converted into waste materials and eliminated from the body (Smith & Anderson, 1986).



Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.