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3.36: Biochemical Compound Classification

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The opening image is a model of an important chemical compound. Without it, living things would not have the energy they need to survive. Compared with most other compounds in living things, molecules of this compound are small and simple. In the model, the gray circles represent carbon atoms, the red circles represent oxygen atoms, and the black circles represent hydrogen atoms.

Q: What is the chemical formula for this compound, and what is its name?

A: The chemical formula is C 6 H 12 O 6 , and the name of the compound is glucose. In this article you’ll learn more about glucose and other compounds that are essential to life.

Introduction to Biochemical Compounds

Glucose is an example of a biochemical compound. The prefix bio- comes from the Greek word that means “life.” A biochemical compound is any carbon-based compound that is found in living things. Biochemical compounds make up the cells and tissues of living things. They are also involved in all life processes, including making and using food for energy. Given their diversity of functions, it’s not surprising that there are millions of different biochemical compounds.

Q: Plants make food in the process of photosynthesis. What biochemical compound is synthesized in photosynthesis?

A: Glucose is synthesized in photosynthesis.

Virtually all living things use glucose for energy, but glucose is just one of many examples of biochemical compounds that are found in most or all living things. In fact the similarity in biochemical compounds between living things provides some of the best evidence for the evolution of species from common ancestors. A classic example is the biochemical compound called cytochrome c. It is found in all living organisms because it performs essential life functions. Only slight variations in the molecule exist between closely related species. The molecule is identical in humans and their closest relatives, the chimpanzees. And even between humans and the single-celled tetrahymena in the picture below, the cytochrome c molecule is nearly 50 percent the same.

Structure of Biochemical Molecules

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. Polymers are large molecules that consist of many smaller, repeating molecules, called monomers. Glucose is a monomer of biochemical compounds called starches. In starches and all other biochemical polymers, monomers are joined together by covalent bonds, in which atoms share pairs of valence electrons.

Size of Biochemical Molecules

Most biochemical molecules are macromolecules. The prefix macro- means “large,” and many biochemical molecules are very large indeed. They may contain thousands of monomer molecules. The largest known biochemical molecule is called titin. It plays an important role in muscle contraction. The human form of the molecule contains more than 34,000 monomers. Its chemical formula is C 169723 H 270464 N 45688 O 52243 S 912 . Its chemical name contains almost 190,000 letters, and it has been called the longest word in any language. Its chemical name is read rapidly in the video at the following URL—and the video lasts more than 8 minutes!

http://www.youtube.com/watch?v=Fx0kMizIioI

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 the Table below . For a video introduction to the classes, go to this URL: http://www.youtube.com/watch?v=_CXeG5qe8sc

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 reactions 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).

Practice

Choose one of the classes of biochemical compounds and do a Web quest to learn more about it. You may want to start with one of the following URLs. Make a list of the main points you discover as you work through your Web quest.

http://en.wikipedia.org/wiki/Carbohydrate

http://en.wikipedia.org/wiki/Protein

http://en.wikipedia.org/wiki/Lipid

http://en.wikipedia.org/wiki/Nucleic_acid

Review

  1. What is a biochemical compound?
  2. Give a general description of a biochemical molecule.
  3. List the four classes of biochemical compounds.
  4. Which classes of biochemical compounds store energy in living things?
  5. Which classes of biochemical compounds contain oxygen?

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Difficulty Level:

At Grade

Grades:

7 , 8

Date Created:

Nov 14, 2012

Last Modified:

Sep 05, 2014
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