Structure and Function of Large Biological Molecules

1. Structure and Function of Large Biological Molecules

2. Macromolecules • 4 main types: carbohydrates, lipids, proteins, nucleic acids • Large molecules typically made of smaller subunits • Carbs, Nucleic acids, proteins = Polymers – built from monomers

3. Synthesizing and Decomposing Macromolecules: Both processes use enzymes! • Dehydration Synthesis: “adding” monomers together to form a polymer. • Removal of an H2O molecule covalently bonds the monomers. • Hydrolysis: Breaking down of polymers into smaller subunits using water. • The H bonding to one monomer and the OH bonding to the other.

4. Carbohydrates Sugars and sugar chains – the fuel and building materials of life

5. Monosaccharides: Simple Sugars Sugar units have empirical formula: CH2O C chains range from 3-7 Enantiomers – different sugars! 5-6 C typically are aromatic!

6. Glucose is Life • C1 and C5 bond to form ring • Glucose is a primary cellular fuel source for respiration • Glucose is also used as a building block for many other macromolecules • Can be stored for later use as di- and polysaccharides • 2 forms of the rings α and β http://pslc.ws/macrog/kidsmac/toon_glu.htm

7. α-glucose and β-glucose

8. Disaccharides Through Dehydration Synthesis • 2 monosaccharides bonded • Glycosidic linkage formed by dehydration synthesis • Disaccharides: maltose, sucrose, lactose • Linkages are named by the carbons that bond • Maltose is a 1-4 glycosidic linkage • Sucrose is a 1-2 glycosidic linkage

9. Types of Glycosidic Linkages 1–4glycosidiclinkage Maltose 1–2glycosidiclinkage Sucrose

10. Polysaccharides – huge chains of monosaccharides • Each monomer is added through dehydration synthesis • Huge chains are good for storage and even structure • Function of the poly- determined by type of linkage and sugar monomers

11. Storage Polysaccharides • Plants create starch for storage • Glucose monomers = stored energy • Stored in plastids • Formed by 1-4 glycosidic linkages

13. Storage Polysaccharides • Animals synthesize glycogen • Glucose monomers – high branched • Stored in liver and muscle

14. Structural Polysaccharides Cellulose – major component of cell walls Most abundant organic molecule on earth Glucose monomers – different linkages! Different forms of glucose but same 1-4 linkage!

15. Cellulose: Tough Cell Walls… Why? • Cellulose is straight chains and never branched • Form parallel chains • Different enzymes to digest! • Fiber  • Chitin = exoskeletons

16. Lipids Hydrophobic, diverse molecules

17. Lipid Basics: Hydrophobic energy chains Lipids are diverse in function but similar in their hydrophobicity Typically have large regions that are hydrocarbon chains

18. Building Blocks of Fats • Fatty acid chains • Glycerol

19. Triacylglycerol (TAGs) AKA Triglycerides Ester linkage! Dehydration Synthesis! x3

20. Saturated and Unsaturated Fats Naturally occurring fatty acids have cis double bonds

22. Cis vs Trans Fats

24. Figure 5.12 Choline Hydrophilic head Phosphate Glycerol Fatty acids Hydrophobic tails Hydrophilichead Hydrophobictails (a) Structural formula (b) Space-filling model (c) Phospholipid symbol

25. Figure 5.13 WATER Hydrophilichead Hydrophobictail WATER

26. Steroids • Steroids have 4 carbon ring structures • Can be hormones or cholesterol

27. Proteins Multiple units, multiple uses

28. Functions of Protein • Proteins account for ~50% of the dry mass of most cells • Proteins act as catalysts, play roles in defense, storage, transport, and cellular communication • Greatest diversity in structure and function

29. Figure 5.15-a Enzymatic proteins Defensive proteins Function: Protection against disease Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysisof bonds in food molecules. Example: Antibodies inactivate and help destroyviruses and bacteria. Antibodies Enzyme Virus Bacterium Storage proteins Transport proteins Function: Storage of amino acids Function: Transport of substances Examples: Hemoglobin, the iron-containing protein ofvertebrate blood, transports oxygen from the lungs toother parts of the body. Other proteins transportmolecules across cell membranes. Examples: Casein, the protein of milk, is the majorsource of amino acids for baby mammals. Plants havestorage proteins in their seeds. Ovalbumin is theprotein of egg white, used as an amino acid sourcefor the developing embryo. Transportprotein Amino acidsfor embryo Ovalbumin Cell membrane

30. Figure 5.15-b Hormonal proteins Receptor proteins Function: Response of cell to chemical stimuli Function: Coordination of an organism’s activities Example: Receptors built into the membrane of anerve cell detect signaling molecules released byother nerve cells. Example: Insulin, a hormone secreted by thepancreas, causes other tissues to take up glucose,thus regulating blood sugar concentration Receptorprotein Signalingmolecules Insulinsecreted Highblood sugar Normalblood sugar Structural proteins Contractile and motor proteins Function: Support Function: Movement Examples: Motor proteins are responsible for theundulations of cilia and flagella. Actin and myosinproteins are responsible for the contraction ofmuscles. Examples: Keratin is the protein of hair, horns,feathers, and other skin appendages. Insects andspiders use silk fibers to make their cocoons and webs,respectively. Collagen and elastin proteins provide afibrous framework in animal connective tissues. Actin Myosin Collagen Muscle tissue Connectivetissue 100 m 60 m

31. Protein Building Blocks - Peptides • All proteins are made of 20 different amino acids • Amino end • Carboxyl end • R = functional group αCARBON

32. Proteins are Polypeptides • Polymers of peptides are made through the formation of peptide bond • Carboxyl end of one AA bonds to the amino end of adjacent AA • Dehydration reaction to form peptide bond • N terminus (+) and C terminus (-)

33. Nonpolar side chains; hydrophobic Side chain(R group) Figure 5.16 Isoleucine (Ile or I) Glycine(Gly or G) Leucine(Leu or L) Alanine(Ala or A) Valine(Val or V) Methionine(Met or M) Phenylalanine(Phe or F) Tryptophan(Trp or W) Proline(Pro or P) Polar side chains; hydrophilic Threonine(Thr or T) Serine(Ser or S) Cysteine(Cys or C) Tyrosine(Tyr or Y) Asparagine(Asn or N) Glutamine(Gln or Q) Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid(Asp or D) Glutamic acid(Glu or E) Histidine(His or H) Lysine(Lys or K) Arginine(Arg or R)

34. Figure 5.16a Nonpolar side chains; hydrophobic Side chain Isoleucine(Ile or I) Valine(Val or V) Alanine(Ala or A) Glycine(Gly or G) Leucine(Leu or L) Methionine(Met or M) Phenylalanine(Phe or F) Tryptophan(Trp or W) Proline(Pro or P)

35. Polar side chains; hydrophilic Figure 5.16b Threonine(Thr or T) Serine(Ser or S) Cysteine(Cys or C) Tyrosine(Tyr or Y) Asparagine(Asn or N) Glutamine(Gln or Q)

36. Figure 5.16c Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Glutamic acid(Glu or E) Histidine(His or H) Aspartic acid(Asp or D) Lysine(Lys or K) Arginine(Arg or R)

37. Figure 5.17 Dehydration synthesis Peptide bond New peptidebond forming Side chains Side chains vary in their charge, polarity, length Back-bone Peptidebond Carboxyl end(C-terminus) Amino end(N-terminus)

38. Protein – Structure Dictates Function • 3D structure of each protein is unique • Structure dictates function • Structure is determined due to 4 levels of folding • Most fundamental level of folding is sequence of AA

39. Figure 5.19 Antibody protein Protein from flu virus

41. Primary Structure AA Sequence Sequence of AA Read in order from N to C Dictates secondary, tertiary, quaternary levels

42. Secondary Structure • Regions of a peptide chain that are coiled or folded into patterns • Regulated by H bonding of atoms in the peptide backbone • α-Helix • β-sheets

44. Tertiary Structure Overall shape of a protein Stabilized by R groups and how they interact Hydrophobic Interactions Disulfide Bridges

45. Quaternary Structure The interaction of multiple polypeptide chains Forms a functional protein Separate peptide chains

46. Chaperonins: Protein Folders

48. Protein Structure in a Cell • Folding is spontaneous • Other proteins aid in this process • Denaturation – unraveling/misfolding of a protein

49. Nucleic Acids Blueprints of life

50. Nucleotides • Monomers of nucleotides • 2 types: DNA and RNA • Deoxyribonucleic acid • Ribonucleic acid