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Chapter 5 The Structure and Function of Macromolecules

Chapter 5 The Structure and Function of Macromolecules. 3 themes are emphasized Hierarchy of structural levels Emergent properties Form fits function. Polymers. Monomers- units that comprise a polymer

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Chapter 5 The Structure and Function of Macromolecules

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  1. Chapter 5The Structure and Function of Macromolecules 3 themes are emphasized Hierarchy of structural levels Emergent properties Form fits function

  2. Polymers • Monomers- units that comprise a polymer • Polymer- long molecule consisting of many similar or identical building blocks linked by covalent bonds

  3. Polymer formation • Condensation reaction- linking of monomers through the loss of a water molecule (dehydration reaction)

  4. Polymer formation • One molecules provides the hydroxyl group (-OH) and the other the hydrogen (-H). • Requires energy and enzymes

  5. Polymer disassembly • Hydrolysis- dissemble polymers • Water is added to break a bond • Ex: digestion- food polymers broken down by enzymes

  6. Classes of Polymers • Carbohydrates • Lipids • Proteins • Nucleic Acids • Other

  7. Carbohydrates • Monomers called monosaccharides • Cellular use: energy, energy storage, structure • (C, 2H, O)n • Monosaccharides, disaccharides, and polysaccharides

  8. Monosaccharides • Glucose • Aldehydes and ketones • Linear and ring forms

  9. Disaccharides • 2 monosaccharides, sucrose = glucose+fructose • Joined by a condensation synthesis called a glycosidic linkage.

  10. Polysaccharides • Several hundred or more monosaccharides • Energy storage: starch and glycogen • Structural: cellulose and chitin

  11. Starch • Storage of polysaccaharides in plants, made up glucose monomers • Provides a way to store surplus glucose, energy can be withdrawn by hydrolysis • Humans have enzymes that can hydrolyze plant starch. High sources of starch found in potatoes, grains (wheat, corn, rice).

  12. Glycogen • Used by animals to store glucose. • More extensively branched than plant starch. • Stored mainly in liver and muscle cells. Humans can only store enough energy for about a day.

  13. Cellulose • Polysaccharide used by plants from structure. • Similar to starch except in the location of the glucose bond: • Starch- alpha linkage, helical shape • Cellulose- beta linkage, straight shape • Opposing hydroxyl groups bond with other strands, creating strong fibers.

  14. Why don’t humans eat grass?

  15. Chitin • structural polysaccharide used by arthropods (insects, spiders, crustaceans) to build their exoskeleton • Also used by fungi rather than cellulose for their cell walls. • Similar to cellulose except has a nitrogen appendage to the glucose.

  16. Lipids • Fats • Not polymers but Large molecules, composed of smaller molecules, assembled by dehydration reactions • Not soluble in water. C-H bonds are non polar

  17. Triglycerides • Fat molecule = Triacylglycerol (or triglyceride) • Triacyglycerol= Glycerol + 3 fatty acids • Linked by ester linkage (condensation reaction) • Oils and fats

  18. Animal fat vs. Plant and Fish fat • Saturated fat vs unsaturated fat • Animal fat- usually saturated- solid at room temperature • Plant and fish fat- usually unsaturated- liquid at room temperature

  19. Fat- what is it good for? • Fat- stores energy • 1 gram of fat stores 2x energy as starch • Stored in adipose cells • Cushions vital organs • Provide insulation

  20. Phospholipids • 2 fatty acids + phosphate group + glycerol

  21. Phospholipids • Various molecules attach to the phosphate group  • Tails are hydrophobic • Heads are hydrophilic • What do they do in water?

  22. Phospholipids • When added to water- they self assemble so that they shield their hydrophobic tails • Micelle- phospholipid droplet, phosphate heads on the outside, tails are restricted to the water-free interior • Phospholipid bilayer- major component of cell membranes

  23. Steroids • Four interlocking carbon rings • Regulatory molecules- sex hormones • Cholesterol-precursor of many steroids • Cholesterol is a component of cell membranes • Cholesterol can contribute to atherosclerosis

  24. Proteins • Monomers called amino acids • 20 different amino acids • Joined by peptide linkage • Chains of amino acids- polypeptide • Function as support, storage, transport, signaling, defense, movement, and catalysts • C, H, O, N, S • Make up 50% of cellular DRY weight

  25. Tens of thousands different types in humans • Enzymes- regulate metabolism, accelerate chemical reactions

  26. Amino Acid Structure • Contains 3 functional groups • Amino, carboxyl and R groups • Polar, nonpolar, charged and uncharged

  27. Amino acid linkage • Peptide bond- covalent bond catalyzed by a dehydration reaction

  28. Amino end: N-terminus Carboxyl end: C-terminus

  29. “Polypeptide” vs “Protein” • Protein- one or more polypeptides twisted, folded, and coiled.

  30. Four Levels of Protein Organization • Primary- sequence of amino acids

  31. Sequence determines function • 20 different amino acids • Lysozyme- protein that helps fight bacteria • 129 amino acids long • 20129 possible combinations • Sickle cell disease is caused by one protein substitution in the structure of hemoglobin.

  32. Four Levels of Protein Organization • Primary- sequence of amino acids • Secondary- coils or folds

  33. Secondary- coils and folds • Result from hydrogen bonding on the backbone of the chain (not the R groups) • Oxygen and nitrogen are electronegative with partial negative charges. • Hydrogen molecules attached to Nitrogen have partial positive charges.

  34. Secondary coil • Alpha helix- delicate coil held together by hydrogen bonding between every fourth amino acid

  35. Secondary Fold • Beta pleated sheet- two or more parallel chains. Held together by hydrogen bonds of the backbone.

  36. Four Levels of Protein Organization • Primary- sequence of amino acids • Secondary- coils or folds • Tertiary- R group interaction

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