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Lipids

Lipids. A. Classified based on solubility (like dissolves like). 1. insoluble in polar solvents. 2. soluble in nonpolar solvents. 3. lipids are hydrophobic. B. Triglycerides (fats and oils). 1. contain fatty acids. a. -COOH functional group at end of a carbon chain.

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Lipids

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  1. Lipids A. Classified based on solubility (like dissolves like) 1. insoluble in polar solvents 2. soluble in nonpolar solvents 3. lipids are hydrophobic

  2. B. Triglycerides (fats and oils) 1. contain fatty acids a. -COOH functional group at end of a carbon chain b. always have an even number of carbons c. can be saturated (with H) d. can be unsaturated have C=C double bonds polyunsaturated

  3. B. Triglycerides (cont.) 2. contain glycerol a. is a 3-carbon alcohol b. has 3 -OH functional groups

  4. C. Triglyceride synthesis 1. -COOH groups react with -OH groups form covalent bonds

  5. 2. fats: solid at room temperature usually saturated 3. oils: liquid at room temperature mostly unsaturated from plants

  6. 4. the greater the unsaturation, the lower the melting point (more likely to be liquid at room temp.)

  7. D. Phospholipids 1. one fatty acid replaced with a -PO4 functional group 2. has both hydrophobic and hydrophilic portions (amphiphilic/amphipathic)

  8. E. Steroids 1. all have basic structure of 4 rings of carbon 2. differences are in functional groups and their locations 3. cholesterol is the precursor for animal steroids

  9. Protein A. Polymer of amino acids 1. 20 naturally occurring amino acids - eight of these are “essential” in humans

  10. 2. three components a. amino group b. carboxyl group c. R group accounts for the 20 different amino acids

  11. B. Amino acids are linked together by peptide bonds. Polymers > 100 amino acids long may be considered proteins

  12. C. Size glucose (carb) = C6H12O6 hemoglobin = C2952H4664O832N812S8Fe4

  13. Figure 3.14A–D Protein structure (layer 1) Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala His Glu Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids

  14. Figure 3.14A–D Protein structure (layer 2) Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala His Glu Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids Hydrogen bond O H H O C C C N N H C O C C C R C N N C H H H O N C O C C C C N O H C H C N N O H C C H H C C N N O N O C N H C N H O O C R C C C O H O H H C C O C C N H O N C C N C C H O C O H N C C O N H H C C H N O H N O N C C C N O C H N H N C C H O O C C C N C C H C N O H C O Alpha helix Pleated sheet

  15. Figure 3.14A–D Protein structure (layer 3) Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala His Glu Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids Hydrogen bond O H H O C C C N N H C O C C C R C N N C H H H O N C O C C C C N O H C H C N N O H C C H H C C N N O N O C N H C N H O O C R C C C O H O H H C C O C C N H O N C C N C C H O C O H N C C O N H C H C H N O H N O N C C C N O C H N H N C C H O O C C C N C C H C N O H C O Alpha helix Pleated sheet Polypeptide (single subunit of transthyretin) most tertiary structures are either globular or fibrous

  16. Figure 3.14A–D Protein structure (layer 4) Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala His Glu Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids Hydrogen bond O H H O C C C N N H C O C C C R C N N C H H H O N C O C C C C N O C H H C N O N H C C H H C C N N O N O C N H C N H O O C R C C C O H O H H C C O C C N H O N C C C N C H O C O H N C C O N H C H C H N O H N O N C C C N O C H N H N C C H O O C C C N C C H C N O H C O Alpha helix Pleated sheet Polypeptide (single subunit of transthyretin) Transthyretin, with four identical polypeptide subunits

  17. examples having quaternary structure: hemoglobin, collagen

  18. Biological Functions of Proteins • Enzymes (globular) • Structural molecules (fibrous) Also: • Regulatory molecules (hormones and transmitters) • Transport (hemoglobin) • Protection (keratin, antibodies) • Movement (muscle fibers)

  19. A given type of protein will have a unique amino acid sequence. - like different combinations of letters create different words A protein typically has only a single function in nature. - an antibody can’t do the job of a muscle fiber (etc).

  20. Shape of a protein determines which molecules can bind to it. The 3-D shape of a protein determines its function. Change shape  Change function

  21. Protein Denaturation • Unfolding of proteins due to chemicals, changes in pH, and/or increased temperature

  22. Protein Denaturation • Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes • - think of an egg white

  23. Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala His Glu Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Hydrolysis “Breakdown” to individual amino acids Breakage of peptide bonds

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