Bio Exam 1 Lecture 1 9 Elements cannot be broken down into simpler substance combinations of elements in different proportions smallest part of a compound retaining its properties smallest unit of an element retaining its properties Atoms Compounds Molecules Atoms of each element have a characteristic number of protons The number of protons equals the number of electrons in an uncharged atom Atomic mass Atomic number sum of protons and neutrons protons and electrons Isotope 2 atoms of an element that differ in number of neutrons Same chemical prop erties but different physical properties Electrons occupy shells electrons in lower shells have less energy Each shell had orbitals and each orbital can hold 2 electrons The first shell has one orbital and can hold only 2 electrons the next 2 shells have 4 orbitals and can hold a maximum of 8 electrons Valence the number of electrons to gain or lose Atoms attempt to gain or lose electrons until outer shell has 8 paired electrons Atoms stabilize by sharing electrons Covalent bond Non polar covalent bond equal sharing of electrons between 2 identical atoms Polar covalent bond one atom has the electrons more often electronegativity when an electron is stolen NaCl s covalent bond between H and N O or F covalent 70 100 ionic 10 20 Hydrogen 4 5 van der walls O H and N H covalent bonds are polar with oxygen and nitrogen holding a partial negative charge and the hydrogen having a partial positive charge C C and C H cova lent bonds are nonpolar H H C H C C O O difference O H N H Ionic bonds Hydrogen bond Bond Strength 1 2 Molecular Weight Mole Molarity Solvent Solute sum of atomic weights of atoms in a molecule amount of compound equal to molecular weight in grams moles of solute dissolved in a liter of solution M m L the dissolving substance the substance being dissolved Killo 1000 milli 10 3 micro 10 6 Equilibrium when there is no net change in the concentrations of reactants and products A B C D Keq CD AB Water hydrogen bonds to other water molecules polar covalently Ice expands upon freezing hydrogen bonds are stable ice formation warms the water and is less dense measures the total kinetic energy Water is both cohesive sticks to itself and adhesive sticks to something else Heat Temperature Specific heat change 1 degree C measure of heat intensity C amount of heat needed to lose or gain for the temperature to Water has specific heat because of hydrogen bond ability High specific heat of water minimizes temperature fluctuation Evaporative cooling control when water evaporates the liquid is cooled temperature Hydrophilic Hydrophobic Ionic substances dissociate when they dissolve in water and hydrophobic sub water loving dissolves in water polar covalent or ionic water hating does not dissolve non polar covalent sances in general become coated with water molecules interactions of partial charges when dissolved or in contact with water dissolve in water yeilding H and an anion donates protons dissolves and produces hydroxyl ion accepts protons Acid HCL H Cl Base NaOH Na OH pH scale measure of dissolved H concentration neutral when H OH pH log H Strong Acid Strong Base Weak acids and bases do not dissociate completely they are buffers minimize pH change gain or lose electrons depending on pH Buffers pH 7 HCl pH 7 NaOH Carbon has a valence of 4 and participates in covalent bonds with H N and O These covalent bonds are largely nonpolar H has one electron to share N has 3 and O has 2 Organic molecules have a carbon skeleton C can bond to itself by either a single or double bond and have H O N and a few other atoms attached to C Isomers Structural isomers Geometric isomers same chemical formula but different structures and properties differ in the covalent arrangement of the same atoms the same atoms and bonds but different arrangement around the double bond cis on the same side of the bond trans on the opposite side Enantiomers differ in arrangement of 4 groups around a C Hydroxyl OH polar hydrogen bond with water Carbonyl C sugars Carboxyl OH C O acidic Amino NH2 base Sulfhydryl SH react forming covalent bonds stabilizes lose H Phosphate O negative charge double bond on one O high energy O P O O Methyl CH3 non reactive non polar Biological macromolecules are built by condensation dehydration reactions and broken down by hydrolysis single CH2O linear or cyclic Carbs sugars contain a carbonyl group aldehyde or ketone monosaccharide disaccharide polysaccharide Carbs contain 1 or more asymmetric carbons and so can exist as enantiomers double formed from 2 monosaccharides by dehydration polymers mono joined by glycosidic bonds Glucose is a 6 C monosaccharide sucrose is a disaccharide composed of glu Glucose forms 2 important polysaccharides Starch glycogen and Cellulose Starch is used for energy storage and celluose is used in plants to build cell Starch is composed of 1 4 linked a glucoses with occasional 1 6 linked side cose and fructose walls chains Cellulose is composed of multiple chains of 1 4 linked B glucoses different glu cose enantiomer than found in starch and the individual chains are hydrogen bonded together which makes cellulose highly resistant to dehydration hydrolysis Fats glycerol and fatty acids glycerol is a 3 C alcohol with hydroxyl group on each C Fatty acid is carboxyl attached to C skeleton 1 fatty acid attached to each OH in glycerol with an ester bond 2 fatty acids and phosphate group attached to glycerol lipids with 4 C C rings Phospholipids Steroids Saturated fats Unsaturated fats double bonds 3 fatty acids stack together solid butter 1 or more unsaturated fatty acids plants and fish liquid oil All lipids are hydrophobic but phospholipids have a double character by having a charged polar head group and a long hydrophobic tail Cell membranes are composed of phospholipid bilayers in which the hydrophobic tails of the phospholipids cluster together on the inside of the bilayer and the hy drophilic heads with the charged phosphate group project outward where they can in teract with water Proteins are polymers of amino acids Each kind has a unique amino acid com position different order in which the amino acids are strung together cells contain thousands of different kinds of proteins and each has a specific cellular function Amino acids are linked together by peptide bonds to make polypeptides carboxyl and amino groups are joined together by dehydration into a C N bond sequence of amino acid chain looks like one line Proteins
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