1. Proteins – Monomer: Amino acids – Polymer: Polypeptide (aka protein) – Key Elements: C, H, N, “R” (R varies) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Proteins are: a)Hydrophobic b)Hydrophilic c)Could be either d)Not sure

2. Protein Functions Proteins are >50% of the dry mass of most cells – Structural support – Storage – Transport – Cellular communications – Movement – Defense against foreign substances – ALL enzymes are proteins – chemical reactions wouldn’t occur in our cells without proteins! Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Proteins have many diverse functions; they are the most functionally diverse type of macromolecules 1. Structural support (e.g. silk of spider webs) 2. Storage of energy & nitrogen (e.g. egg albumin) 3. Transport of substances within organisms (e.g. hemoglobin) or across membranes (e.g. aquaporins) 4. Signaling: long-distance (e.g. insulin) or short-distance; gene-regulatory proteins; receptor proteins Functions of Proteins: Examples

4. Proteins have many diverse functions; they are the most functionally diverse type of macromolecules 5. Defense against invading pathogens (e.g. antibodies in immune system) Antibody proteinProtein from flu virus 6. Movement (e.g. muscle proteins) ATP Actin and Myosin

5. Fig. 8.16 Enzymes speed up chemical reactions 7. Metabolic catalysts (enzymes)

6. Beans and other legumes Corn (maize) and other grains Lysine Essential amino acids Tryptophan Isoleucine Leucine Phenylalanine Threonine Valine Methionine Fig. 41.2 So, a diet of only wheat bread and corn would not be sufficient.

7. Peptide bond is C-N bond between neighboring amino acids formed by removal of H 2 O (dehydration synthesis). Since amino acids in proteins are bonded together by peptide bonds, proteins are also called polypeptides. Peptide bond Peptide bond Side chains Backbone Fig. 5.18

8. LevelsLevels of protein structure Fig. 5.21 Primary Structure Secondary Structure Tertiary Structure  pleated sheet Examples of amino acid subunits  helix Quaternary Structure imagecent.com; alison.knitsmiths.us; bigtopshirtshop.com

9. Exact sequence of amino acids is called the primary structure of a protein. Fig. 5.21 Amino acid subunits 25 20 15 10 5 1 Primary Structure

10. Levels of protein structure Fig. 5.21 Primary Structure Secondary Structure Tertiary Structure  pleated sheet Examples of amino acid subunits  helix Quaternary Structure

11. Fig. 5.21 SecondarySecondary Structure  pleated sheet  helix Secondary structure: Helix or pleated sheet.

12. Pleated sheet protein often used for structural purposes Spider’s abdominal glands secrete silk fibers made of structural protein with  pleated sheets. Fig. 5.21

13. Levels of protein structure Fig. 5.21 Primary Structure Secondary Structure Tertiary Structure  pleated sheet Examples of amino acid subunits  helix Quaternary Structure

14. Polypeptide backbone TertiaryTertiary structure results from various kinds of interactions between atoms of the side chains (R groups). Fig. 5.21

15. Levels of protein structure Fig. 5.21 Primary Structure Secondary Structure Tertiary Structure  pleated sheet Examples of amino acid subunits  helix Quaternary Structure

16. Polypeptide chain  Chains Heme Iron  Chains Collagen Hemoglobin Fig. 5.21 Quarternary Quarternary structure is the interaction of different subunits.

17. Changes in primary structure can have a profound effect on protein function. Primary structure Secondary and tertiary structures Function Quaternary structure Molecules do not associate with one another; each carries oxygen. Normal hemoglobin (top view)  subunit Normal hemoglobin 7 65 432 1     GluValHis Leu ThrPro Glu Fig. 5.22

18. Primary structure Secondary and tertiary structures Function Quaternary structure Molecules do Not stick to each other; each carries oxygen Normal hemoglobin  subunit Normal hemoglobin 7 65 432 1     GluValHis Leu ThrPro Glu Molecules crystallize into fiber; capacity to carry oxygen greatly reduced Sickle-cell hemoglobin Sickle-cell hemoglobin 765 4 3 2 1     Val HisLeuThrProGlu Fig. 5.22 Exposed hydrophobic region

19. Nonpolar R groups: hydrophobic Glycine Alanine ValineLeucine Isoleucine Fig. 5.17 Amino acid R (rest) groups Arginine Histidine Aspartic acid Glutamic acid Lysine Electrically Charged R groups: hydrophilic

20. Primary structure Secondary and tertiary structures Function Quaternary structure Molecules do Not stick to each other; each carries oxygen Normal hemoglobin  subunit Normal hemoglobin 7 65 432 1     GluValHis Leu ThrPro Glu Molecules crystallize into fiber; capacity to carry oxygen greatly reduced Sickle-cell hemoglobin Sickle-cell hemoglobin 765 4 3 2 1     Val HisLeuThrProGlu Fig. 5.22 Exposed hydrophobic region

21. Normal red blood cells are full of individual hemoglobin molecules, each carrying oxygen. Fibers of abnormal hemoglobin deform red blood cells into sickle shape. 10 µm Fig. 5.22

22. The Genetics of Sickle Cell Anemia Sickle cell anemia is a recessive disorder. AA (homozygous dominant) don’t have symptoms. aa (homozygous recessive) have severe symptoms, including: Low body oxygen levels Severe pain Swelling of hands and feet Frequent infections (spleen) Delayed growth/development Vision problems What about heterozygotes (Aa)? Usually lack negative effects, but high stress situations can trigger symptoms Healthyyounow.com

23. Why hasn’t natural selection eliminated sickle cell anemia? Some clues: 1 in 10 African Americans is a carrier for sickle cell anemia Rates of sickle cell anemia are also higher in people with Mediterranean, Middle Eastern, and Indian ancestry

24. Individuals with two copies of the altered gene suffer many complications (pain, infections, stroke, etc.), but are resistant to malaria. Individuals with one copy suffer few complications and are also resistant. Sickle-cell disease inheritance. http://en.wikipedia.org/wiki/Sickle-cell_disease 0–2.5% Distribution of malaria caused by Plasmodium falciparum (a parasitic unicellular eukaryote) Frequencies of the sickle-cell allele 2.5–5.0% 7.5–10.0% 5.0–7.5% >12.5% 10.0–12.5% Fig. 23.17 “Heterozygote Advantage”

25. Nonpolar R groups: hydrophobic Glycine Alanine ValineLeucine Isoleucine Fig. 5.17 Amino acid R (rest) groups Arginine Histidine Aspartic acid Glutamic acid Lysine Electrically Charged R groups: hydrophilic

26. Today’s Exit Ticket The bonds creating the primary structure of a protein are called 1)___________ and form between a 2)___ atom in one amino acid and a 3)____ atom in another amino acid. The bonds creating the secondary structure of a protein are called 4)__________ and form between 5)___________. The bonds creating the tertiary structure of a protein can be covalent, ionic, or hydrogen bonds, and form between 6)_______________. 7) Describe the quaternary structure of a protein.