Ashley SefretJanuary 29, 2013BSCI105 – Class Notes MONDAY WEDNESDAY GSS BSCI 105 7-8pm BPS 1228CHEMICAL PRINCIPALS – lecture 2 1/29/13 - What is an element? o Substance that cannot be broken down into other chemical substanceso Compounds are substances that contain 2 or more elements in a fixed ratio (ex H2O)o There are 92 naturally occurring elementso 96% of human body weight consists of only 4 elements (oxygen 65%, carbon 18.5%, hydrogen 9.5%, nitrogen 3.3%) o 7 other elements make up almost all the resto Only 5 or 6 in the human body- Elements are made up of Atomso Nucleus: one or more protons and one or more neutronso Electrons: charge: -1o Number of electrons = number of protonso Number of neutrons is not necessarily = to that of the number of protons/electrons- Electrons are predominantly found in orbitalso Orbitals hold electrons: First orbital: 2 Second orbital: 8 Third orbital: 8o Outermost orbital is called valence shell – an atom is stable when the valenceshell has a full complement of electronso May be filled by: Electrons of the same atom (ex Argon) Electrons shared with another atom (covalent bond) Electrons abstracted from another atom (one atom will take an electronfrom another atom giving the first a negative charge) (ionic bond) LOOK IN NOTES AT DIAGRAM 1 - Polar vs Nonpolar Bondso Atoms differ in their affinity for electrons aka electronegativity (the greater the electronegativity, the greater the desire to pick up more electrons)o Electronegativity is an atoms desire to attract electronso In a water molecule, the Oxygen will have a partial negative charge bc its more electronegativeo Two atoms with different affinities form a covalent bond, the electrons in the bond will be shared equally and it becomes a polar covalent bondo When electrons are equally shared and their affinities are roughly equal, bondsare nonpolar covalent bondso Periodic table: electronegativity increases as you go up and as you go right - Nonpolar, Polar, and Ionic BondsDifference in electronegativity andbond strengthBond examples0-0.5 strong Non polar: C-H0.6-2 weaker Polar: O-H, N-HMore than 2 weakest Ionic: NaCl- Hydrogen Bonds: Hydrogen Atom Shared by 2 electronegative atomso Hydrogen bond between water H2O and Ammonia NH3 when water has a partial positive charge and ammonia has a partial negative charge when it shares a proton- Water’s Hydrogen Bonding Network: one water molecule with covalent bonds between the hydrogens and oxygen forms a hydrogen bond with the hydrogen of another water molecule LOOK AT DIAGRAM 2- Formation of Ions from Water Molecules: DIAGRAM 3: o Acids: have the ability to release protons + o Bases: have the ability to absorb protons – - pH Scale indicates Acidityo pH=-log10 [H+]o in pure water [H+]=10^-7M. pH=7o Higher the pH the greater the basicityo Lower the pH the greater the acidity o pH of acidic solutions is less than 7o pH of basic solutions is greater than 7- Bufferso Help solutions maintain pHo Buffers contain salts that contain either a weak acid or a weak baseo Ex phosphate, bicarbonate, TUMS neutralize the acid in your stomachChemical Structures of Biological Molecules – lecture 3 1/31/13 - Most biomolecules have a carbon skeleton – look at diagram 4o Structure defines function - Functional Groups are the Reactive Parts of Biological Moleculeso Estradiol and Testosterone are steroidso Different structure and different functional groups determine different biological propertieso Hydroxyl Structure: –OH or HO– Alcohols; names usually end in –ol Diagram 5 Polar bc oxygen is more electronegative Can form hydrogen bonds w water molecules, helping dissolve organinc compounds like sugaro Carbonyl Diagram 6 Ketones if the carbonyl group is within a carbon skeleton Aldehydes if the carbonyl group is at the end of the skeleton (connectsto a hydrogen) Ketone and aldehyde are found in sugars, giving rise to 2 major groups of sugars: ketoses and aldoseso Carboxyl Diagram 7 Carboxylic acids, or organic acids Acts as a acid; can donate a proton (H+) bc the covalent bond betweenoxygen and hydrogen is so polar Found in cells in the ionized formo Amino Diagram 8 Amines Acts as a base Pick up a proton (H+) Can be nonionized or ionized (positively charged) Found in cells in the ionized form with a charge of 1+o Sulfhydryl Diagram 9 Thioles Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein Cross linking of cysteines in hair protiens maintains curliness or straightnesso Phosphate Diagram 10 Organic phosphates Contributes negative charge to the molecule of which it is a part (2- when at the end of a molecule; 1- when within a chain of phosphates) Have potential to react w water, releasing energyo Methyl Diagram 11 Methylated compounds Addition of a methyl group- Biopolymers are synthesized in dehydration reactionso Diagram 12o When a polymer connects with a monomer, a water molecule is released and amacromolecule is created- Biopolymers are broken down in hydrolytic reactionso When a macromolecule breaks down, hydrolysis adds a water molecule- Carbohydrates: Structure, Synthesis, and Breakdowno Primary source of metabolic energy (ex starch)o Chemical formula: (CH2O)no Monomer: monosaccharideo Dimer: disaccharideo Polymer: polysaccharideo Names end in –ose except for glycogeno Many isomers (isomers have the same chemical formula, different 3D conformations)- Families of Carbohydrates: o Aldose (Aldehyde Sugar) – c=o at end of moleculeo Ketose (Ketone Sugar) – c=o in middle of moleculeo Carbonyl groups: C doublebonded O o Trioses – 3-carbon sugars (C3H6O3) Dihydroxyacetone (ketose) Glyceraldeyde (aldose)o Hexoses – 6-carbon sugars (C6H12O6) Linear and ring forms becomes abbreviated ring structures, cyclic by forming aldehyde bond Ex: Glucose and Galactose [aldoses] (even tho same structure, OH is on diff sides, so hteyre diff); and Fructose (Ketone) Look at figure 5.4 in textbook- You link together monosaccharides to make disaccharides (polymerizing) thru a dehydration reactiono Glucose + glucose = maltose and an H2O molecule; maltose is the two glucose molecules connected by a glycosidic linkage -O-o Glucose (aldose) + Fructose (ketose) = sucrose and an H2O molecule- Storage carbohydrates: o Starch – a plant polysaccharide, found in
View Full Document
Unlocking...