Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 3 Molecules of a cell Molecules 2 types – Organic – Inorganic Organic- generally C based Inorganic- generally non-C based ** Exceptions include CO2, CO, CN, etc C-H H H • Hydrocarbons – Compounds composed of only C and H Methane, propane, butane, benzene, etc H C C H H H H H C C C H H H Ethane H Propane Carbon skeletons vary in length. H C H H H H H H C C C C H H H H H H H H H C C H H C H H Butane Isobutane Skeletons may be unbranched or branched. H H H C C C H H H H C • Chain, branch or ring of C – C skeleton H H H H H H H H C C C C H H H 1-Butene 2-Butene Skeletons may have double bonds, which can vary in location. H H H H C H H H C C C C C H H H C H H C H C H H Cyclohexane C H C C H Benzene Skeletons may be arranged in rings. H Isomers Compounds with the same formula different structures – Different shapes = unique properties Functional Groups • Determine the properties of organic compounds • Polar – O and N exert a “strong pull” on shared electrons – Hydrophilic Functional Groups • • • • • • Hydroxyl- OH Carbonyl- C=O Carboxyl- COOH Amino- NH2 Phosphate- OPO32Methyl- CH3 Biological Molecules 4 primary classes 1. 2. 3. 4. Carbohydrates Lipids Proteins Nucleic acids These molecules are large (dozens to millions of C) = macromolecules 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 Making Polymers • Cells link monomers to form polymers via a dehydration reaction 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+ Breaking Polymers • Cells break polymers into monomers via a hydrolysis reaction 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 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 OH H OH HO H H H H H OH O OH OH H Glucose OH Glucose H2O CH2OH CH2OH O O H H OH H HO H H H O OH OH H OH H Maltose H H OH • • • • Monosaccharides- one monomer (glucose) Disaccharides- two monomers (sucrose) Oligosaccharides- several monomers Polysaccharides- hundreds of monomers Sugar uses • Starch and glycogen: Nutritional Store chemical energy – Starch in plants – Glycogen in animals 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 Sugar Storage Glucose monomer STARCH Starch granules in potato tuber cells O O O O O O O Glycogen granules in muscle tissue O O O O GLYCOGEN O O O O O O O O O O O O Cellulose fibrils in a plant cell wall CELLULOSE O Cellulose molecules O O OO O OH OO OO O OH O OO OO Figure 3.7 O O O O O O O O Lipids • No true monomer – some are formed via dehydration reactions • Fats, Steroids, Phospholipids • Energy storage, membrane function • Hydrophobic 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 C C OH OH H C H OH Glycerol HO C O H2O CH2 CH2 CH2 CH2 CH2 Fatty acid CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 H H H H C C C O O O C O C O C H O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH3 CH CH2 CH2 CH2 CH2 CH2 CH2 CH3 Figure 3.8C Figure 3.8B Fatty Acids • Simple lipids containing 2 parts – Long hydrocarbon chain (non-polar, hydrophobic) – Carboxylic acid functional group (polar, hydrophilic) 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 Kinky • Double bonds kink the structure • Kinks reduce packing density • Lower packing density decreases melting point 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 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. Trans Fats • Naturally occurring unsaturated fats are cis: hydrocarbon chain is kinked. • Trans fats are straight. 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. 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 Phospholipids Hydrophilic/Hyrdophobic • Cell membrane is bilayer of phospholipids • Hydrophilic “head” • Hydrophobic “tail” Waxes • Long fatty acid tails bonded to long-chain alcohols or carbon rings – Tightly packed – Water-repelling Steroids • Rigid backbone of 4 C rings and no fatty acid tail – Present in all eukaryote cell membranes – Often hormones – Cholesterol is an example Waxes • Long fatty acid tails bonded to long-chain alcohols or carbon rings – Tightly packed – Form waterproof coating 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 Amino Acids • Specific properties based on its structure H H H O N H C H C CH2 O N OH C H O C N OH H CH CH3 H OH CH2 CH2 OH C OH Serine (Ser) Hydrophobic O Aspartic acid (Asp) Hydrophilic Figure 3.12B C H CH3 Leucine (Leu) C Functions of Proteins Enzymes Structural Contractile Defensive Signal Receptor Transport Storage **Significant in the plasma membrane Form determines function • One or more polypeptide chains folded into a unique shape – Unique shape determines the function Groove Groove 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 Gly Thr Primary structure Gly Val Lys Ala Glu Phe His Val Ser Lys Val Leu Asp Ala Val Amino acids Pro Arg Gly Ser 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 &Hydrogen pleated sheets Amino acids bond O H C N C C C N H C O N H N O Secondary structure C H O C C O H O C N H C O C N O H O C N H C O H CC O C C N H N R H N H C O H C C N N O C CN H C H C N CC N C H H CC N O H C C N H O C O C C N H C O O O C R N H N C C N H C H CC O H C C O O H N C N C C O CN C H O C H Alpha helix Figure 3.14B Pleated sheet H C N C O N C Levels of Protein Structure • Tertiary – Overall threedimensional shape of a polypeptide – Globular or fibrous Tertiary structure Polypeptide (single subunit of transthyretin) Levels of Protein Structure • Quaternary structure – Results from the association of two or more Polypeptide chain polypeptide chains Quaternary structure Transthyretin, with four identical polypeptide subunits Collagen 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 Prions • Prions result from misfolded proteins • Infectious proteins – Can cause other proteins to misfold Enzymes • Catalysts – Increase rate of chemical reactions in cells Nucleic Acids H • Monomer= nucleotides H N N N H OH O P N O CH2 Nitrogenous base (A) O O Phosphate group H H H H OH Sugar N H H – Storage and transmission of genetic information – Two types of nucleic acids • DNA and RNA • OPO32• CH3 added to DNA affects expression 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 C C T G G A T C G A T T A Base pair G T A A T A C T DNA & RNA • Five types of nitrogenous bases – Purines and Pyrimidines – DNA = A,T,G and C – RNA = A,U,G and C 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