Amino acids are organic molecules that contain an amine functional group —NH 2 , a carboxylic acid functional group —COOH , and a side chain that is specific to each individual amino acid. Most living things build proteins from the same 20 different amino acids. Amino acids connect by the formation of a peptide bond, which is a covalent bond formed between two amino acids when the carboxylic acid group of one amino acid reacts with the amine group of the other amino acid.
The formation of the bond results in the production of a molecule of water in general, reactions that result in the production of water when two other molecules combine are referred to as condensation reactions.
The resulting bond—between the carbonyl group carbon atom and the amine nitrogen atom is called a peptide link or peptide bond. Since each of the original amino acids has an unreacted group one has an unreacted amine and the other an unreacted carboxylic acid , more peptide bonds can form to other amino acids, extending the structure Figure 4.
A chain of connected amino acids is called a polypeptide. Proteins contain at least one long polypeptide chain. Figure 4. This condensation reaction forms a dipeptide from two amino acids and leads to the formation of water.
Figure 5. A computer rendering shows the three-dimensional structure of the enzyme phenylalanine hydroxylase. In the disease phenylketonuria, a defect in the shape of phenylalanine hydroxylase causes it to lose its function in breaking down phenylalanine. Enzymes are large biological molecules, mostly composed of proteins, which are responsible for the thousands of metabolic processes that occur in living organisms.
Enzymes are highly specific catalysts; they speed up the rates of certain reactions. Enzymes function by lowering the activation energy of the reaction they are catalyzing, which can dramatically increase the rate of the reaction. Most reactions catalyzed by enzymes have rates that are millions of times faster than the noncatalyzed version.
Like all catalysts, enzymes are not consumed during the reactions that they catalyze. Enzymes do differ from other catalysts in how specific they are for their substrates the molecules that an enzyme will convert into a different product. Each enzyme is only capable of speeding up one or a few very specific reactions or types of reactions.
Since the function of enzymes is so specific, the lack or malfunctioning of an enzyme can lead to serious health consequences. One disease that is the result of an enzyme malfunction is phenylketonuria. In this disease, the enzyme that catalyzes the first step in the degradation of the amino acid phenylalanine is not functional Figure 5. Untreated, this can lead to an accumulation of phenylalanine, which can lead to intellectual disabilities.
Kevlar Figure 6 is a synthetic polymer made from two monomers 1,4-phenylene-diamine and terephthaloyl chloride Kevlar is a registered trademark of DuPont. Kevlar is typically spun into ropes or fibers. The material has a high tensile strength-to-weight ratio it is about 5 times stronger than an equal weight of steel , making it useful for many applications from bicycle tires to sails to body armor. The material owes much of its strength to hydrogen bonds between polymer chains refer back to the chapter on intermolecular interactions.
There is additional strength derived from the interaction between the unhybridized p orbitals in the six-membered rings, called aromatic stacking. Figure 7. The diagram shows the polymer structure of Kevlar, with hydrogen bonds between polymer chains represented by dotted lines. Kevlar may be best known as a component of body armor, combat helmets, and face masks.
Kevlar is also used to protect armored fighting vehicles and aircraft carriers. Civilian applications include protective gear for emergency service personnel such as body armor for police officers and heat-resistant clothing for fire fighters. Kevlar based clothing is considerably lighter and thinner than equivalent gear made from other materials Figure 8. Figure 8.
Kevlar is also used to make b canoes and c marine mooring lines. In addition to its better-known uses, Kevlar is also often used in cryogenics for its very low thermal conductivity along with its high strength. The table here summarizes the structures discussed in this chapter:. The addition of nitrogen into an organic framework leads to two families of molecules.
Compounds containing a nitrogen atom bonded in a hydrocarbon framework are classified as amines. Compounds that have a nitrogen atom bonded to one side of a carbonyl group are classified as amides. Amines are a basic functional group. Amines and carboxylic acids can combine in a condensation reaction to form amides. Trimethyl amine: trigonal pyramidal, sp 3 ; trimethyl ammonium ion: tetrahedral, sp 3. Skip to main content. Module Organic Chemistry. Search for:. Amines and Amides Learning Outcomes Describe the structure and properties of an amine Describe the structure and properties of an amide.
DNA in Forensics and Paternity The genetic material for all living things is a polymer of four different molecules, which are themselves a combination of three subunits. Watch this video animation of how DNA is packaged for a visual lesson in its structure. Addictive Alkaloids Since ancient times, plants have been used for medicinal purposes.
The plant produces these substances, collectively called secondary plant compounds, as chemical defenses against the numerous pests that attempt to feed on the plant: In these diagrams, as is common in representing structures of large organic compounds, carbon atoms in the rings and the hydrogen atoms bonded to them have been omitted for clarity.
Proteins and Enzymes Proteins are large biological molecules made up of long chains of smaller molecules called amino acids. Kevlar Kevlar Figure 6 is a synthetic polymer made from two monomers 1,4-phenylene-diamine and terephthaloyl chloride Kevlar is a registered trademark of DuPont. Figure 6. This illustration shows the formula for polymeric Kevlar.
Key Concepts and Summary The addition of nitrogen into an organic framework leads to two families of molecules. What is the hybridization of the nitrogen atom in trimethyl amine and in the trimethyl ammonium ion?
What are the geometries and hybridizations about the nitrogen atoms in pyridine and in the pyridinium ion? Write two complete balanced equations for the following reaction, one using condensed formulas and one using Lewis structures.
Methyl amine is added to a solution of HCl. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. Read more about how to correctly acknowledge RSC content. Fetching data from CrossRef. This may take some time to load. Loading related content. Jump to main content. Jump to site search. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page.
Issue 27, From the journal: Physical Chemistry Chemical Physics. This article is Open Access. Please wait while we load your content Something went wrong. Try again? Cited by.
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