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Transcript
Chapter 3 Molecules of a cell Quiz 1 • Answer the questions that you got wrong 1. Correct answer 2. Why that is the correct answer 3. Get back half the points you missed *** Q 3 and Q 4 Hypotheses • Tentative, testable statement that proposes a possible outcome/explanation to an event TESTABLE!!!! A tentative relationship is stated, not just a prediction. Predictions are not necessarily testable Prediction vs Hypothesis • Predictions “guess” what will happen • Hypothesis presents a relationship, which explains what will happen • ***Hypotheses do not draw conclusions – Ex: Squirrels are different colors at different locations due to diet differences because this lets them blend into their surroundings. Language of a hypothesis • Contain the dependent and independent variables – If leaf color change is related to temperature , then exposing plants to low temperatures will result in changes in leaf color. • If the reader cannot figure out what you are testing, it is not a hypothesis • Can be in “If- Then” format, but it does not have to be Hypotheses • • • • • • The coral snake’s bright color pattern serves to warn off potential predators. The king snake suffers less predation because it mimics or looks like the coral snake. The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes. Rotting meat produces flies The markings on the winds of flies increase survival of flies by causing spiders to flee If fermentation rate is related to temperature, then increasing the temperature will increase gas production Bonds Type e- Ionic taken/received Covalent shared atoms neutral polar shared atoms partial nonpolar shared atoms neutral shared molecules neutral Hydrogen links? overall charge atoms pos/neg 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 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 Methane, propane, butane, benzene, etc 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 • Chain, branch or ring of C H H H C 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. – C skeleton 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 Ex: 16 isomers of C6H12O4, but only one, d- Glucose, is used in metabolism 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= 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 H OH OH OH Short polymer H H Unlinked monomer Dehydration Dehydration reaction reaction H2O OH OH H H Longer polymer Dehydration Reaction • Removes water – Unlinked monomers have a hydroxyl group (-OH) at one end & a hydrogen (-H) at the other • For each monomer added, 1 molecule water is removed • Held via covalent bonds **2 monomers are contributing to the H20 molecule One monomer looses a hydroxyl group and the other looses a H atom Dehydration Reaction H OH OH OH Short polymer H H Unlinked monomer Dehydration Dehydration reaction reaction H2O OH OH H H Longer polymer Breaking Polymers • Cells break polymers into monomers via a hydrolysis reaction H2O H OH Hydrolysis H OH OH H 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 Hydrolysis Reaction H2O H OH Hydrolysis H OH OH H Enzymes • Catalysts • Macromolecules that increase rate of chemical reactions in cells • Typically proteins Sugar! • Carbohydrates are polymers called saccharides • Monosaccharides contain one monomer (glucose) • Disaccharides contain two monomers (sucrose) • Oligosaccharides contain several monomers • Polysaccharides contain hundreds of monomers Disaccharides • Cells link two single sugars to form disaccharides – Monosaccharides can join to form disaccharides using dehydration reactions • Such as sucrose (table sugar) and maltose (brewing sugar) CH2OH CH2OH O O H H H H OH H H H OH H O OH HO H H 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 Sugar storage • Starch and glycogen store polysaccharides – Starch in plants – Glycogen in animals • Cellulose 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 • Not true polymers, although some are formed via dehydration reactions • Hydrophobic • Energy storage • Solid and liquid states Fats • Triglycerides • Energy storage • Consist of glycerol linked to three fatty acids 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) – Carboxylic acid functional group (polar) Polar and nonpolar character in one molecule: which wins? Hydrocarbon chain dominates • Length of hydrocarbon chain means that nonpolar character dominates – Fatty acids dissolve in nonpolar solvents Saturated vs Unsaturated • Double bonding between C prevents H from bonding to the C skeleton – 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: – Two fatty acids – One phosphate group and small organic molecule • Hydrophilic and Hydrophobic portion – Created water resistant membrane Phospholipids Hydrophilic/Hyrdophobic • Cell membrane is bilayer of phospholipids • Hydrophilic “head” • Hydrophobic “tail” • Steroids Steroids & Waxes – C skeletons contain 4 fused rings – Often hormones – Cholesterol is an example • Waxes form waterproof coating H3C CH3 CH3 HO CH3 CH3 Proteins • Polymer constructed from amino acid monomers • Amino acids contain: – -NH2. – -COOH. – R groups (R varies from one amino acid to another). • Link between amino acids in protein is a peptide bond Proteins Functions of Proteins • Multiple functions – – – – – – – – Enzymes Structural Contractile Defensive Signal Receptor Transport Storage Building Proteins • Built from amino acids (AA) – 20 AA • Amino acids form chain with R groups from side chains – R group determines protein variety 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 Amino Acids • Cells link AA together via dehydration synthesis – Bonds broken via hydrolysis • Bonds between monomers are peptide bonds – 2 bonded AA= dipeptide – > 2 bonded AA= polypeptide Carboxyl group H H H O N H C Peptide bond Amino group C + OH O H N C Dehydration reaction H C H N OH R R Amino acid Amino acid H2O H H O C C R H N C H R Dipeptide O C OH Form determines function • A protein consists of one or more polypeptide chains folded into a unique shape – Unique shape of protein 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 – Coiling or folding of the chain, stabilized by H bonding • 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 Tertiary structure – Overall threedimensional shape of a polypeptide – Globular or fibrous – Interactions between R groups 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 – Results from heat, salt concentration, pH, etc. • Resulting altered shape causes proteins to loose their function Nucleic Acids H • Information-rich polymers of 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 – Nucleic acids such as DNA and RNA serve as the blueprints for proteins and thus control the life of a cell – The monomers of nucleic acids are nucleotides DNA & RNA • DNA consists of two polynucleotides – Twisted around each other in a double helix – Held together by hydrogen bonding • RNA consists of a single polynucleotide strand • There are five types of nitrogenous bases – DNA has A,T,G and C – RNA has A,U,G and C 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