A polymer is a large molecule that forms when many smaller molecules are linked together by covalent bonds.

1. Couplers that interlock connect one railroad car to another. Many cars can be joined together to form a train, because there are couplers on both ends of a car.

2. A polymer is a large molecule that forms when many smaller molecules are linked together by covalent bonds. • The smaller molecules that join together to form a polymer are monomers. • In some polymers, there is only one type of monomer. Other polymers have two or more kinds of monomers.

3. What is one way that polymers can be classified? Polymers can be classified as natural polymers or synthetic polymers.

4. Many important types of biological molecules are natural polymers. Organisms produce these polymers in their cells. Synthetic polymers are developed by chemists in research laboratories and manufactured in factories. Both types of polymers have industrial uses. Silk and cotton fabrics are woven from natural polymer fibers, while polar fleece is made from a synthetic polymer.

5. Synthetic Polymers What are three examples of synthetic polymers? Rubber, nylon, and polyethylene are three examples of compounds that can be synthesized.

6. Synthetic Polymers Rubber • The sap collected from rubber trees in tropical regions contains rubber. • Chemists produced a synthetic rubber, using hydrocarbons from petroleum. • Natural rubber and synthetic rubbers contain different monomers and have different properties.

7. Synthetic Polymers Nylon • Research to make artificial silk led to nylon, which has properties not found in natural polymers. • Nylon fibers are very strong, durable, and shiny. • Nylon is used in parachutes, windbreakers, fishing line, carpets, and ropes.

8. Synthetic Polymers Polyethylene Polyethylene forms when ethene (or ethylene) molecules link head to tail. The number of carbon atoms in a polyethylene chain affects the properties of the polymer. The more carbon atoms in the chain, the harder the polymer is.

9. Synthetic Polymers A Rubber is used to manufacture tires. B Nylon fibers are strong and do not wear out easily. C Hard plastic shapes can be made from a polyethylene polymer.

10. Natural Polymers What are four types of polymers that organisms can produce? Four types of polymers produced in plant and animal cells are starches, cellulose, nucleic acids, and proteins.

11. Natural Polymers Starches Simple sugars have the formula C6H12O6. They can exist as straight chains or rings. Fructose and glucose can react to form sucrose (table sugar). Glucose monomers join to form starches as shown below.

12. Natural Polymers Simple sugars, slightly more complex sugars such as sucrose, and polymers built from sugar monomers are all classified as carbohydrates. Typically, a starch contains hundreds of glucose monomers. Plants store starches for food and to build stems, seeds, and roots.

13. Natural Polymers All the foods shown contain starch, which is a polymer of the simple sugar glucose.

14. Natural Polymers Cellulose • The carbohydrate cellulose is the main component of cotton and wood. • Cellulose molecules contain 3000 or more glucose monomers. • Cellulose gives strength to plant stems and tree trunks.

15. Natural Polymers Nucleic Acids Nucleic acids are large nitrogen-containing polymers found mainly in the nuclei of cells. There are two types of nucleic acid, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids in each cell of a plant or animal store information about its structures and functions.

16. Natural Polymers The monomers in a nucleic acid are nucleotides. • A DNA nucleotide has three parts: a phosphate group, deoxyribose sugar, and an organic base. • When two strands of DNA line up, pairs of bases are arranged like the rungs of a ladder.

17. Natural Polymers The strands in DNA are held together by strong intermolecular attractions between hydrogen atoms on one strand and nitrogen or oxygen atoms on the other strand. • The strands twist around each other in a structure called a double helix. • The order of the base pairs in a strand is a code that stores information that is used to produce proteins.

18. Natural Polymers

19. Natural Polymers Proteins Organic acids contain a –COOH group, and organic bases contains an –NH2 group. An amino acid is a compound that contains both carboxyl and amino functional groups in the same molecule.

20. Natural Polymers There are about 20 amino acids that your body needs to function. They include glycine and phenylalanine.

21. Natural Polymers Your cells use amino acids as the monomers for constructing protein polymers. • A protein is a polymer in which at least 100 amino acid monomers are linked through bonds between an amino group and a carboxyl group. • The instructions for making proteins are stored in DNA. • Your body may contain as many as 300,000 different proteins.

22. Natural Polymers These foods are all good protein sources.

23. Assessment Questions • A synthetic polymer that can be formed into strong fibers suitable for making cloth and rope is • silk. • high-density polyethylene. • natural rubber. • nylon.

24. Assessment Questions • A synthetic polymer that can be formed into strong fibers suitable for making cloth and rope is • silk. • high-density polyethylene. • natural rubber. • nylon.ANS: D

25. Assessment Questions • The strong natural fiber, cellulose, is a polymer made of long chains of what type of molecule? • amino acid • organic bases • hydrocarbons • sugar

26. Assessment Questions • The strong natural fiber, cellulose, is a polymer made of long chains of what type of molecule? • amino acid • organic bases • hydrocarbons • sugar ANS: D

27. Assessment Questions • A large molecule that forms when many smaller molecules are linked together by covalent bonds is a monomer. TrueFalse

28. Assessment Questions • A large molecule that forms when many smaller molecules are linked together by covalent bonds is a monomer. TrueFalse ANS: F, polymer