Proteins are polymers of amino acids. There are approximately twenty different types of amino acids. Proteins can vary in length from two amino acids to a chain of millions of amino acids (polypeptide). 

 Two amino acids synthesized together = dipeptide 

 Three amino acids synthesized together = tripeptide 

 Four to billions amino acids synthesized together = polypeptides or protein 

 Examples of protein are hair, claws of reptiles, birds and mammals, egg albumin, gelatin, etc. 

 In order to understand proteins let us examine the general structure of amino acids. 

three amino acids 

Amino Acid Structure: Amino acids consist of a carbon skeleton consisting of one carbon with three attached groups. Carboxyl group - this in the functional group studies earlier. -(-COOH) The carboxyl group will be on one end of the amino acid molecules and will provide the -OH group to form water during condensation synthesis of amino acids to form protein. Identify this group in the figure above. Amine group - this is the functional group studied earlier. (-NH ) The amino group will be on the opposite end of the amino acid as the carboxyl group and will provide the -H group to form water during the condensation of synthesis of amino acids to form protein. Identify this group in the figure above.  "R" group - this group may be any of the twenty different groups of atoms which provide the protein with its characteristics. This group in the figure above is located in the boxes. Your text will show a few of these twenty different types.  These groups vary is structure, thus there are twenty different types of amino acids. 

amino acids 

The above figure contains the structural formula for three amino acids. Fine the amino group, carboxyl group and the "R" group. The "R" group is outlined in white. In nature their are approximately twenty different types of amino acids based on the "R" groups. These "R" groups produce the chemical properties of the amino acids and the proteins which they makeup. 

 17. In your notes draw a figure showing the general structural formula of an amino acid. 

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Amino acids are hooked together to forming covalent bonds between the amino acid monomers. This is accomplished as discussed earlier by condensation synthesis. Let us review condensation synthesis: During the process of condensation synthesis one water molecule between each monomer will be removed. Each monomer contributes part of the water molecule that is released; one monomer loses a hydroxyl group (OH), and the other loses a hydrogen (H). Both monomers, having each lost a covalent partner, now bond covalently with each other. This time the OH is removed from the carboxyl group of one amino acid and the H is removed from the amino group of a second acid amino acid. Trace the events described above using the figure below. 

  Note:  The "R" groups are indicated  by "R1, R2, etc". They are not drawn out. 

 18. How many water molecules will be formed when four amino acids condense to form a protein molecules? 

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In your notes using structural formulas write a reaction hooking three amino acids together during a synthesis condensation reaction. 

 Note that the bond which forms during the synthesis of two or more amino acids contains a C-N-C bond since water is cleaved between an amino group and an organic acid group. This bond is called a peptide bond. It exists only in proteins. Locate the two peptide bonds in the protein molecule below. 

 19. How many peptide bonds does a tripeptide contain? Press here to check your answer. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

  
Not only do different protein contain different lengths of amino acids, but the amino acids can be arranged in any order. Therefore their is almost an infinite number of proteins. 

 The precise sequence of amino acids in a protein is called its primary structure. 

 20.  What is the primary structure of the following protein? 

 ser-gly-gly-glut-arg-thre 

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21. Protein can also be hydrolyzed. If you had eggs for breakfast this morning the protein of the egg albumin (egg white) is in your large intestine. This protein is now being hydrolyzed (digested) into what products? 

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Nucleic Acids: DNA/RNA 
Read the pages in the text indicated by A-10 and reexamine behavior objectives 27. Nucleic acids are macromolecules which contain the elements carbon, hydrogen, oxygen, nitrogen and phosphorus. Like protein and starch these are linear polymers. The monomers which are covalently bonded are called nucleotides. Examine the figures of nucleotides and nucleic acids which are found in your readings. Nucleotides are made of the following parts: 

 five carbon sugar - ribose or deoxyribose - these sugars are present in the form of a five sided ring. 

 phosphate- this is the functional group discussed earlier 

 nitrogen-containing base - there are five different types of bases found in nucleic acids 

 Examine the figure below and locate each of the nucleotide parts. 

nucleotide 

 These nucleotide can be hooked together by condensation synthesis forming a polymer of nucleic acids. When these monomers link by condensation synthesis the phosphate group links to the sugar group forming a long polymer of P-S-P-S-P-S-P-S with the nitrogenous base sticking above the polymer. 

 There are two type of nucleic acids DNA and RNA. Chemical differences between these two nucleic acids will be discussed in miniunit Delta. 

 DNA- macromolecules are used for gene expression and the control of all cellular activities by directing protein synthesis. The structure and function of this molecule will be studied in miniunit Delta. 

 RNA - macromolecules are used to aid the DNA molecules during gene expression. They are also act as messengers and transfer molecules during protein synthesis. 

 Nucleic acids can also be hydrolyzed. 

 22. The hydrolysis of nucleic acids form: 

 
          a) amino acids 
          b) fatty acids 
          c) fructose 
          d) nucleotides 

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This is the end of miniunit Alpha. You may now go back to the Miniunit Alpha Lessons Page and take the practice test. 
 

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