1. Chapter 5 The Structure and Function of Macromolecules

2. I. Macromolecules Polymer = large molecule made by covalently linking together many monomers Monomers = individual building blocks Classes of polymers: Polysaccharides (carbohydrates) Polypeptides (proteins) Polynucleotides (nucleic acids: DNA & RNA) Other macromolecules - not technically polymers Lipids (fats)

3. The Synthesis and Breakdown of Polymers Condensation reaction – joins two monomers with a covalent bond dehydration reaction (remove a water molecule) Hydrolysis - reverse of the dehydration reaction; break two monomers apart by adding back a water molecule Animation: Polymers Animation: Polymers

4. LE 5-2 Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new bond Dehydration reaction in the synthesis of a polymer Longer polymer Hydrolysis adds a water molecule, breaking a bond Hydrolysis of a polymer

5. The Diversity of Polymers Each cell has thousands of different kinds of macromolecules & macromolecules vary among cells of an organism, within a species, and even more between species An immense variety of polymers can be built from a small set of monomers 1 2 3 HOH

6. II. Carbohydrates ~ fuel and building material Carbohydrates ~ sugars and sugar polymers Monosaccharides = single sugars Polysaccharides = polymers composed of many monosaccharide building blocks Animation: Organic Models

7. Monosaccharide Sugars Monosaccharides: CH 2 O Ex: Glucose C 6 H 12 O 6 Monosaccharide characteristics: 1. Hydroxyl groups (-OH) 2. Carbonyl group (p. 70) Carbonyl group Aldoses (aldehyde) Ketoses (ketone) 3. Linear or rings (in water) Linear or rings 4. Names end in “-ose” Names end in “-ose” # C – triose, pentose, hexose Ex: glucose is a hexose & aldosemonossacharide

8. Disaccharides Disaccharide = dehydration reaction joins two monosaccharides Bond = glycosidic linkage

9. Polysaccharides Polysaccharides = polymers of many monosaccharide sugars The structure and function (storage or structural) of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages Animation: Carbohydrates

10. Storage Polysaccharides Starch = storage polysaccharide of plants α-glucose monomers 1-4 linkages Helical Ex: amylose (unbranched) & amylopectin (branched) Plants store surplus starch as granules within chloroplasts and other plastids

11. LE 5-6a ChloroplastStarch 1 µm Amylose Starch: a plant polysaccharide Amylopectin

12. Glycogen = storage polysaccharide in animals α-glucose 1-4 linkages Helical MORE EXTENSIVE BRANCHING than starch Humans and other vertebrates store glycogen mainly in liver and muscle cells

13. LE 5-6b Mitochondria Glycogen granules 0.5 µm Glycogen Glycogen: an animal polysaccharide

14. Structural Polysaccharides Cellulose = component of plant cell walls Β-glucose 1-4 linkages Straight chains, unbranched Grouped into microfibrils Humans cannot digest cellulose (“fiber”) Some microbes can (symbiosis in herbivores)

15. LE 5-8 Cellulose molecules Cellulose microfibrils in a plant cell wall Cell walls Microfibril Plant cells 0.5 µm  Glucose monomer

17. Chitin = structural polysaccharide found in: exoskeleton of arthropods cell walls of many fungi Glucose monomers with nitrogen appendages

18. III. Lipids Lipids - class of large biological molecules that do not form polymers The unifying feature of lipids: hydrophobic consist mostly of hydrocarbons, which form nonpolar covalent bonds The most biologically important lipids: Fats Phospholipids Steroids Animation: Lipids

19. Fats Fat = triglyceride Glycerol = 3-carbon alcohol 3 Fatty acids = carboxyl group attached to a long carbon skeleton Joined by an Ester Linkage

20. LE 5-11b Ester linkage Fat molecule (triacylglycerol or triglyceride)

21. Fatty acids can vary in : length (# carbons) number and locations of double bonds Saturated fatty acids = no double bonds (max # H); solid fats Unsaturated fatty acids = one or more double bonds; liquid oils The major function of fats is energy storage and protection (adipose)

22. Phospholipids Phospholipid = two fatty acids and a phosphate group are attached to glycerol Solubility: Hydrophilic Head = charged phosphate group Hydrophobic Tails = the two fatty acids

23. Phospholipids In water, they form a bilayer hydrophobic tails pointing toward the interior Similar to arrangement found in cell membranes

24. Steroids Steroids = lipids with four fused carbon rings Ex: Cholesterol ~ a component in animal cell membranes Precursor for steroid hormones

25. IV. Nucleic Acids Nucleic acids = polymers called polynucleotides Monomers are nucleotides Nucleotide = a nitrogenous base, a pentose sugar, and a phosphate group Nucleoside = portion of a nucleotide w/out phosphate group Nucleotide

26. Nitrogenous Bases Nitrogenous bases: Attached to 1 st C of sugar Two classes: Pyrimidines = 1 ring  Cytosine (C), Thymine (T), Uracil (U) Purines = 2 rings fused  Adenine (A), Guanine (G)  Base Pairing: A – T (or U) and C – G

27. Pentose Sugar & Phosphate  Deoxyribose (DNA) or Ribose (RNA)  Phosphate – attached to 5’ C of sugar

28. Types of Polynucleotides 2 types of nucleic acids: Deoxyribonucleic acid (DNA) Unit of inheritance = gene Provides own directions for replication Ribonucleic acid (RNA) DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis DNA  RNA  protein Phosphodiester linkage between nucleotides between –OH group on the 3´ C of one nucleotide and the phosphate on 5´ C on the next

29. LE 5-25 NUCLEUS DNA CYTOPLASM mRNA Ribosome Amino acids Synthesis of mRNA in the nucleus Movement of mRNA into cytoplasm via nuclear pore Synthesis of protein Polypeptide Animation: Nucleic Acids Functions

30. Polynucleotides (Nucleic Acids) DNA Genetic code Deoxyribose sugar Helical & double* stranded (antiparallel) Hydrogen bonds – hold 2 strands together RNA Ribose sugar Single* stranded Uracil instead of Thymine (bases) *usually Animation: DNA & RNA Structure

32. DNA and Evolution The linear sequences of nucleotides in DNA molecules are passed from parents to offspring Two closely related species are more similar in DNA than are more distantly related species Molecular biology can be used to assess evolutionary kinship

33. V. Proteins Proteins - more than 50% of dry mass of cells Functions include: Enzymes Structural Storage Transport Hormonal (cellular communication) Receptor Contractile (movement) Defensive Animation: Protein Functions Proteins in mouse cells

35. Enzyme - protein that acts as a catalyst, speeding up chemical reactions

36. Polypeptides Polypeptides = polymers of amino acids Protein = one or more polypeptides Monomers = Amino Acids ~ an asymmetric carbon with: carboxyl group Amino group H atom R group (different side chains)

37. Amino Acids 20 different amino acids Chemistry of side chain (R-group) determine characteristics Nonpolar ~ hydrophobic Polar ~ hydrophilic Acidic (-) ~ hydrophilic Basic (+) ~ hydrophilic

38. Amino Acid Polymers Amino acids are linked by peptide bonds to make a polypeptide chain Conformation = the unique 3-D shape determined by the sequence of amino acids A protein’s conformation determines its function

39. Four Levels of Protein Structure Primary ~ sequence of amino acids Primary A gene codes for each sequence Secondary ~ repeated coils (α-helix) and/or folds (β-pleated sheets) in the polypeptide chain Secondary Due to H-bonding along backbone Tertiary ~ irregular folding Tertiary Due to side chain (R-group) interactions Ex: hydrophobic; disulfide bridges; H-bonds, ionic Quaternary ~ 2 or more polypeptide chains interact to make a functional protein Quaternary Ex: collagen and hemoglobin Animation: Protein Structure

40. Sickle-Cell Disease A slight change in primary structure can affect a protein’s conformation and ability to function Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

41. LE 5-21b Primary structure Secondary and tertiary structures 1 2 3 Normal hemoglobin Val His Leu 4 Thr 5 Pro 6 Glu 7 Primary structure Secondary and tertiary structures 1 2 3 Sickle-cell hemoglobin Val His Leu 4 Thr 5 Pro 6 ValGlu 7 Quaternary structure Normal hemoglobin (top view)         Function Molecules do not associate with one another; each carries oxygen. Quaternary structure Sickle-cell hemoglobin Function Molecules interact with one another to crystallize into a fiber; capacity to carry oxygen is greatly reduced. Exposed hydrophobic region  subunit

42. What Determines Protein Conformation? Physical and chemical conditions can affect conformation Alternations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel, or denature, and become biologically inactive Denaturation = loss of a protein’s native conformation due to disrupted secondary, tertiary and quaternary structure PRIMARY STRUCTURE IS STILL INTACT can fold into correct conformation in right environment

43. LE 5-22 Denaturation Renaturation Denatured proteinNormal protein

45. LE 5-4 Linear and ring forms Abbreviated ring structure

46. LE 5-17a Isoleucine (Ile) Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro) Leucine (Leu) Valine (Val) Alanine (Ala) Nonpolar Glycine (Gly)

47. LE 5-17b Asparagine (Asn) Glutamine (Gln)Threonine (Thr) Polar Serine (Ser) Cysteine (Cys) Tyrosine (Tyr)

48. LE 5-17c Electrically charged Aspartic acid (Asp) Acidic Basic Glutamic acid (Glu) Lysine (Lys)Arginine (Arg) Histidine (His)

49. LE 5-20a Amino acid subunits Carboxyl end Amino end

50. LE 5-20b Amino acid subunits  pleated sheet  helix

51. LE 5-20d Hydrophobic interactions and van der Waals interactions Polypeptide backbone Disulfide bridge Ionic bond Hydrogen bond

52. LE 5-20e  Chains  Chains Hemoglobin Iron Heme Collagen Polypeptide chain Polypeptide chain