CK-12 Physical Science Concepts - For Middle School

http://www.ck12.org Chapter 3. Chemical Interactions

Classes of Biochemical Compounds

Although there are millions of biochemical compounds, all of them can be grouped into just four main classes:
carbohydrates, proteins, lipids, and nucleic acids. The classes are summarized in theTable3.8.

TABLE3.8:Classes of Biochemical Compounds

Class Elements Examples Functions

Carbohydrates carbon

hydrogen

oxygen

sugars

starches

cellulose

provide energy to cells

store energy in plants

makes up the cell walls of

plants

Proteins carbon

hydrogen

oxygen

nitrogen

sulfur

enzymes

hormones

speed up biochemical re-

actions

regulate life processes

Lipids carbon

hydrogen

oxygen

fats

oils

store energy in animals

store energy in plants

Nucleic acids carbon

hydrogen

oxygen

nitrogen

phosphorus

DNA

RNA

stores genetic information

in cells

helps cells make proteins

Q:In which class of biochemical compounds would you place glucose?

A:Glucose is a sugar in the class carbohydrates. Like other carbohydrates, it contains only carbon, hydrogen, and
oxygen. It provides energy to the cells of living things.

Q:Look back at the chemical formula for titin. In which class of biochemical compounds should it be placed?

A:Titin is a protein. You can tell because it contains sulfur, and proteins are the only biochemical compounds that
contain this element.

Summary

• Biochemical compounds are carbon-based compounds that are found in living things. The similarity in
  biochemical compounds between living things provides evidence for the evolution of species from common
  ancestors.


• All biochemical molecules contain hydrogen and oxygen as well as carbon. They may also contain nitrogen,
  phosphorus, and/or sulfur. Almost all biochemical compounds are polymers.


• Most biochemical molecules are macromolecules, meaning that they are very large. Some contain thousands
  of monomer molecules.


• Although there are millions of biochemical compounds, all of them can be grouped into just four classes:
  carbohydrates, proteins, lipids, and nucleic acids.

Vocabulary

• biochemical compound: Any carbon-based compound found in living things (carbohydrate, protein, lipid, or
  nucleic acid).