Log In | Register

Key Idea: Plants use sugar molecules to make a variety of larger carbon-containing molecules that become part of their body structures.

Students are expected to know that:

  1. Growth, repair, and replacement of body structures (such as stems, leaves, roots, flowers, fruits, seeds, and the cells of which they are made) involves using sugar molecules to make a variety of larger carbon-containing molecules that become part of the plant’s body structures.
  2. Growth of plants and animals requires the addition of molecules made up of linked carbon atoms to their body structures, and this is the only way that body structures can grow. An increase in size associated with taking up water is not considered to be growth.
  3. The sugar molecules used to make these larger carbon-containing molecules are already inside the plant.
  4. The processes by which sugar molecules are used to make carbohydrates, proteins, and fats involve chemical reactions in which atoms of the sugar molecules are rearranged to form molecules of carbohydrates, fats, and proteins.
  5. Other kinds of atoms from dissolved minerals in the soil (such as nitrogen, and sulfur) are also used and incorporated into the molecules that become part of the plant’s body structures, but in much smaller amounts than the carbon atoms from the sugars. Students should know that the incorporation of minerals into body structures does not produce observable growth.


  1. Items do not assess students’ knowledge of the chemical or structural formulas of carbohydrates, proteins, or fats or the processes by which they are made.
  2. The idea that simple sugars are the “building blocks” of complex carbohydrates, that amino acids are the building blocks of proteins, and that fatty acids are the building blocks of fats is covered in Benchmark 6C/M2, not this key idea.
  3. The idea that water is a major component of cells is part of Benchmark 5C/M4, not this key idea.
  4. The idea that carbon, because of its small size and four available bonding electrons can join to several other carbon atoms in chains and rings to form large and complex molecules is part of Benchmark 5C/H8, not this key idea.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Knowledge Being Assessed Pre-Test Post-Test Select This Item for My Item Bank


The minerals plants take in from the soil make up a very small amount of the new mass of the growing plant.




Aside from water, plant body structures are made up mostly of carbohydrate molecules.




Plants use glucose to build larger molecules (polymers) that make body structures (and water molecules)



Frequency of selecting a misconception

ID Number

Student Misconception

Pre-Test Post-Test


Plants make sugars from minerals (Tamir, 1989) or minerals and water (AAAS pilot data 2006).




Cells are not made up of atoms (Herrmann-Abell & DeBoer, 2008).




Minerals are food for plants (Horizon, n.d.; Vaz et al., 1997).



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.