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Chapter 3

Chapter 3. Molecules of a cell. Molecules. 2 types Organic Inorganic Organic- generally C based Inorganic- generally non-C based ** Exceptions include CO 2 , CO, CN, etc. C-H. Hydrocarbons Compounds composed of only C and H Methane, propane, butane, benzene, etc

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Chapter 3

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  1. Chapter 3 Molecules of a cell

  2. Molecules 2 types • Organic • Inorganic Organic- generally C based Inorganic- generally non-C based ** Exceptions include CO2, CO, CN, etc

  3. C-H • Hydrocarbons • Compounds composed of only C and H • Methane, propane, butane, benzene, etc • Chain, branch or ring of C • C skeleton

  4. Isomers • Compounds with the same formula different structures • Different shapes = unique properties

  5. Functional Groups Determine the properties of organic compounds Polar O and N exert a “strong pull” on shared electrons Hydrophilic

  6. Functional Groups Hydroxyl- OH Carbonyl- C=O Carboxyl- COOH Amino- NH2 Phosphate- OPO32- Methyl- CH3

  7. Biological Molecules 4 primary classes Carbohydrates Lipids Proteins Nucleic acids These molecules are large (dozens to millions of C) = macromolecules

  8. Polymers & Monomers Cells make large molecules by joining together smaller molecules into chains Chains are called polymers Individual molecules are monomers Monomers connect into polymers ***Mono=1 Poly=many Meros= part

  9. Making Polymers Cells link monomers to form polymers via a dehydration reaction

  10. Dehydration Reaction Removes H-O-H For each monomer added, 1 molecule water is removed Held via covalent bonds **2 monomers are contributing to the H20 molecule One monomer looses an OH and the other looses a H+

  11. Breaking Polymers Cells break polymers into monomers via a hydrolysis reaction

  12. Hydrolysis Reaction Breaks covalent bond between monomers by adding water A OH- joins to one monomer and a H joins to an adjacent monomer For each monomer removed, 1 molecule water is added

  13. Sugar! Carbohydrates Monomer is monosaccharide OH & C=O Link two sugars into disaccharide Ex: sucrose (table sugar) and maltose (brewing sugar) CH2OH CH2OH O O H H H H H H OH H OH H O OH H HO OH H OH H OH Glucose Glucose H2O CH2OH CH2OH O O H H H H H H OH OH H H O OH HO H OH H OH Maltose

  14. Monosaccharides- one monomer (glucose) • Disaccharides- two monomers (sucrose) • Oligosaccharides- several monomers • Polysaccharides- hundreds of monomers

  15. Sugar uses Starch and glycogen: Nutritional Store chemical energy Starch in plants Glycogen in animals

  16. Structural Sugar • Cellulose: Structural • Forms the cell walls of plants • Digestible by some animals, but not humans • Chitin forms exoskeletons of insects and crustaceans and cell walls in fungi

  17. Sugar Storage Glucose monomer STARCH Starch granules in potato tuber cells O O O O O O O O O O O Glycogen granules in muscle tissue GLYCOGEN O O O O O O O O O O O O O Cellulose fibrils in a plant cell wall CELLULOSE O O OH Cellulose molecules O O O O O OH O O O O O O O O O O O O O O O O Figure 3.7

  18. Lipids No true monomer some are formed via dehydration reactions Fats, Steroids, Phospholipids Energy storage, membrane function Hydrophobic

  19. Fats Solid and liquid states Consist of glycerol linked to three fatty acids Termed Triacylglycerol Hydrophobic Fatty acid has COOH Glycerol has OH group H H H H H H H H C C H C H H C C C O O O OH OH OH C C C O O O Glycerol HO CH2 CH2 CH2 C O H2O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 Fatty acid CH2 CH2 CH CH2 CH2 CH2 CH2 CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH3 CH3 CH3 Figure 3.8C Figure 3.8B

  20. Fatty Acids Simple lipids containing 2 parts Long hydrocarbon chain (non-polar, hydrophobic) Carboxylic acid functional group (polar, hydrophilic)

  21. Saturated & Unsaturated Double bonding between C prevents H from bonding Fatty acids with double bonds are unsaturated Fatty acids without double bonds are saturated Saturated/unsaturated refers to whether or not the C chains contain the maximum number of H possible

  22. Kinky Double bonds kink the structure Kinks reduce packing density Lower packing density decreases melting point

  23. Saturation and melting point Saturated fatty acids have melting points above 25ºC Liquid at room temp As number of double bonds increases, melting point decreases More likely to be solid at room temp

  24. Hydrogenation Highly unsaturated fats can be very soft and are hydrogenated (saturated) to make them more butter-like. Addition of hydrogen to C=C double bond. Some of the cis bonds are converted to trans.

  25. Trans Fats Naturally occurring unsaturated fats are cis: hydrocarbon chain is kinked. Trans fats are straight.

  26. Buyer Beware Trans fats are straighter than cis fats and the product is stiffer. Trans fats pose a health risk – are not broken down readily.

  27. Phospholipids Significant component of cell membranes Contain a glycerol backbone: Glycerol with two fatty acids Also bonded with P group and another small, polar group Amphipathic properties significant for cell membranes Created water resistant membrane

  28. Phospholipids

  29. Hydrophilic/Hyrdophobic Cell membrane is bilayer of phospholipids Hydrophilic “head” Hydrophobic “tail”

  30. Waxes • Long fatty acid tails bonded to long-chain alcohols or carbon rings • Tightly packed • Water-repelling

  31. Steroids • Rigid backbone of 4 C rings and no fatty acid tail • Present in all eukaryote cell membranes • Often hormones • Cholesterol is an example

  32. Waxes Long fatty acid tails bonded to long-chain alcohols or carbon rings Tightly packed Form waterproof coating

  33. Proteins Monomer= Amino Acids Unique sequence of AA (20 AA in total) Link between amino acids in protein is a peptide bond COOH & NH2 functional groups

  34. Amino Acids Specific properties based on its structure H H H H H H O O O N C C N C C N C C OH OH H H H OH CH2 CH2 CH2 CH OH C CH3 CH3 OH O Leucine (Leu) Serine (Ser) Aspartic acid (Asp) Hydrophobic Hydrophilic Figure 3.12B

  35. Functions of Proteins Enzymes Structural Contractile Defensive Signal Receptor Transport Storage **Significant in the plasma membrane

  36. Form determines function One or more polypeptide chains folded into a unique shape Unique shape determines the function Groove Groove

  37. Levels of Protein Structure Primary Unique sequence of AA forming the polypeptide chain Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Cys Val Lys Phe Ala Glu His Gly Val Ser Lys Primary structure Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids

  38. Levels of Protein Structure Secondary Conformation of portions of the polypeptide chain Conformation- 3-d arrangement of atoms in a molecule (spatial organization) Alpha helix & pleated sheets Hydrogen bond O H H O C C C N N H C O C C C R N C C N H H H O N C C O C C C N O H H C N C N O H C H C H C N N C N O C O N H N C H O O C R C C O C O H H H C C O C N H O N C C C N C H Secondary structure C C O O H N C C O N H C C H H N H N O O N C C N C O C H N H N C C H O C O C C N H C C C N O H C O Alpha helix Pleated sheet Amino acids Figure 3.14B

  39. Levels of Protein Structure Tertiary Overall three-dimensional shape of a polypeptide Globular or fibrous Tertiary structure Polypeptide (single subunit of transthyretin)

  40. Levels of Protein Structure Quaternary structure Results from the association of two or more polypeptide chains Polypeptide chain Quaternary structure Transthyretin, with four identical polypeptide subunits Collagen

  41. When shape fails Denaturation Polypeptide chains unravel, unfold and disorganize Results from heat, salt concentration, pH, etc. Resulting altered shape causes proteins to loose their function

  42. Prions • Prions result from misfolded proteins • Infectious proteins • Can cause other proteins to misfold

  43. Enzymes Catalysts Increase rate of chemical reactions in cells

  44. Nucleic Acids Monomer= nucleotides Storage and transmission of genetic information Two types of nucleic acids DNA and RNA OPO32- CH3added to DNA affects expression H H N N N H OH N H N O P O CH2 Nitrogenous base (A) O O H H Phosphate group H H H OH Sugar

  45. DNA & RNA DNA consists of two polynucleotides twisted around each other in a double helix Held together by hydrogen bonding RNA typically consists of a single polynucleotide strand C A T C G C G A T C G A T A T Base pair G C T A A T A T

  46. DNA & RNA • Five types of nitrogenous bases • Purines and Pyrimidines • DNA = A,T,G and C • RNA = A,U,G and C

  47. Videos • Protein structure • http://www.youtube.com/watch?v=lijQ3a8yUYQ • Carbs • http://www.youtube.com/watch?v=_qf_r5EVP6U&feature=related • http://www.youtube.com/user/greatpacificmedia#p/u/50/_qf_r5EVP6U • Phospholipids • http://www.youtube.com/watch?v=7k2KAfRsZ4Q

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