1. Aim: What is the primary structure of proteins ?

2. What are basic characteristics of proteins ? A) Proteins make up 50 % of the cells weight. B) Proteins functions include: –1. Structural support –2. Storage (of amino acids) –3. Transport (e.g., hemoglobin) –4. Signaling (chemical messengers)

3. What are basic characteristics of proteins ? Proteins functions include: –5. Cellular response to chemical stimuli (receptor proteins) –6. Movement (contractile proteins) –7. Defense against foreign substances and disease-causing organisms (antibodies) –8. Catalysis of biochemical reactions (enzymes)

4. What are basic characteristics of proteins ? C. Proteins are polymers made up of organic monomers called amino acids.

5. What are amino acids ? 1. Amino acids are the building blocks of proteins and enzymes. 2. The basic structure of amino acids includes an amine group, a carboxyl acid group, a central carbon and one of 20 replacement groups.

6. What are amino acids ? 3. There are 20 different replacement groups that fit in the ‘R’ position. –- 9 are nonpolar (hydrophobic, water- insoluble) except glycine –- 6 are polar (hydrophilic, water-soluble) –- 5 are ionic (hydrophilic, water-soluble)

7. Examples of amino acids One group of amino acids has hydrophobic R groups.

8. Examples of amino acids Another group of amino acids has polar R groups, making them hydrophilic.

9. Examples of amino acids The last group of amino acids includes those with functional groups that are charged (ionized) at cellular pH. (The pH of the cell’s cytoplasm is slightly acidic which helps to ionize amino acids.) –Some R groups are bases, others are acids.

10. What are dipeptides ? Dipeptides = larger compounds produced by the dehydration synthesis (condensation) of two amino acids

11. What are dipeptides ? Amino acids are joined together when a dehydration reaction removes a hydroxyl group from the carboxyl end of one amino acid and a hydrogen from the amino group of another. –The resulting covalent bond is called a peptide bond.

12. What are polypeptides ? Polypeptides = may contain 500 + amino acids held together by peptide bonds. All polymers are produced by dehydration synthesis and broken apart by hydrolysis. Enzymes (organic catalysts) are needed for this process to occur.

13. What are proteins ? Proteins are made up of two or more polypeptide chains. These polypeptide chains may be held together by: hydrogen bonds (hemoglobin) hydrogen bonds and disulfide bonds (insulin) Disulfide bonds are covalent bonds that occur when 2 cysteine amino acids come in close contact with one another and the proper enzymes are present to link them together.

14. What are proteins ?