Week 2 of Notes
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This 6 page Class Notes was uploaded by Danielle Francy on Tuesday March 1, 2016. The Class Notes belongs to Bio 190 at Towson University taught by Joseph Velenovsky in Fall 2015. Since its upload, it has received 30 views. For similar materials see Intro Biology for Health Professions in Biology at Towson University.
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Date Created: 03/01/16
Week Two of Notes : Unit 2 Atoms Unreactive atoms: He, Ne Reactive atoms: H, C, N **If outermost electron shell is filled, it will not form bonds. Electrons and Molecules: ● Electrons account for the chemical activity of atoms ● The further an electron is from the nucleus, the greater the energy ● In electron shells, the quantity is based on the atomic number ● The number of electrons in the outer shell determines chemical properties ● Unpaired electrons in the valence shell tend to be reactive ● Complete valence shell elements are chemically inert ● Two atoms with incomplete valence shells will either share, donate, or receive electrons completing valence shells. Covalent bonds: ● Strongest chemical bond, two atoms share one or more pairs of valence shell electrons ● Two or more atoms held together by covalent bonds form a molecule ● Atoms within a molecule are constantly trying to take the electrons they share ● ***An atom’s attraction for shared electrons is calelectronegativity ● The more electronegativity, the more strongly electrons are pulled Electronegativity and Electrons: ● ***hen you give away an electron, you have a positive charge ● Molecules composed of atoms with very different electronegative values ● Oxygen and nitrogen are very electronegative ● In water, oxygen attracts the shared electrons much more than the lesser electronegative hydrogen ● Electrons spend more time near the oxygen atom than the hydrogen atoms ● Unequal sharing of electrons results in polar covalent bond ● Hydrogen is partially positive and oxygen is partially negative due to the unequal sharing of electrons Electrons and Ionic Compounds: ● Atoms can strip an electron or electrons from other atoms ● Difference in electronegativity between sodium and chlorine is large ● Sodium donates electron to chlorine resulting in sodium and chloride formation ● ***Two ions with opposite charges attract and form ionic bond ● Ionic compounds are neutral Hydrogen Bonds: ● Weak, but just as important as covalent bonds ● Most large molecules are held together by weak bonds. These bonds are generally eaily breakable and able to be formed ● Partial charges and water ● Hydrogen bonding in water ● Hydrogen bonds in protein shape and function Chemical Reactions: ● The formation of water is a chemical reaction Properties of Water: ● Cohesion: tendency of molecules of the same composition to stick togetherhydrogen bonding ● Adhesion: ability to cling or stick to other substances (also found in cell walls of plants) ● Water has a high resistance to temperature change, hydrogen bonds must be disrupted, water can absorb a large amount of heat ● Ice is less dense than water ● ***Solution, solvent, solute, aqueous solution ● Solution: a liquid mixture in which the minor component(the solute) is equally distributed within the major component(the solvent). ● Aqueous solution: A solution in which the solvent is water Donations: ● An acid donates ● Carboxyl group acts as an acid which donates an ionized hydrogen ion ● Carboxylic acids, acetic acids ● Amino groups act as bases ● Aminesaccepts ● Phosphate groups, ATP ***Aldehyde, carbon is on the end….Ketone, carbon is in the middle Macromolecules: 1. Carbohydrates 2. Proteins 3. Nucleic Acids ***Lipids areNOT macromolecules ● Monomers and polymers ● Dehydration reaction lose a water molecule ● Hydrolysis add water Dehydration Synthesis: ● Removal of OH from one amino acid and H from the other amino acid, releasing one H2O molecule ● Allows direct covalent linkage between two amino acids ● Water is taken out (dehydration) as a larger molecule is made (synthesis) ● ***Dehydration synthesis to make a polypeptide chain is translation ● The covalent bond between two amino acids(monomers) in a polypeptide (polymer)=peptide bond(amino bond) Protein Hydrolysis: ● Enzyme is required ● loss of primary structure Hydrophilic: Water loving Hydrophobic: Repels with water Enzymes speed up a chemical reaction. Structures of Proteins: Primary Structure: ● Linear chain of amino acids held together in a specific sequence by covalent(“peptide”) bonds(polypeptide) ● Folding occurs spontaneously ● Changes in primary structure may affect the ability of the protein to fold ● ***Upon denaturation, this level of structure is still intact. Secondary Structure: ● Distribution of alpha helices and beta pleated strands along a protein chain ● Spatial arrangement of amino acid residues that are nearby in the sequence/local regions of the polypeptide chains ● Regular coils(helices) and folds(pleated sheets) with connecting segments; Hbond ● Alpha helix and beta pleated sheet are backbones ● Both held together by hydrogen bonding ● ***Amino acids are not involved ● Most globular proteins are made of beta pleated sheets ● Most fibrous proteins are made of alpha helix Tertiary Structure: ● Secondary structure folded into 3D shape ● ***3D structure determines function ● Globular ● Interactions between R groups ● Hydrogen bonding polar side chains; ionic bonding with charged ● Refers to the spatial arrangement of amino acid residues that are a far apart in the sequence and to the pattern of disulfide bonds ○ Hydrophobic side chains are buried in the interior and it’s polar, charged chains are on the surface. Quaternary Structure: ● Refers to the spatial arrangement of subunits and the nature of their interactions ● Functional protein consisting of two or more individual polypeptide chains to assemble into multisubunit structures. ● Two or more polypeptide chains makes one macromolecule ● 4 subunits make up a protein Shorter explanation of the structures: Primary Order of amino acids formed by dehydration synthesis which forms covalent bonds Secondary Alpha helix and Beta pleated sheet along a protein chain. Form is twisted. Hydrogen bonding. TertiaryFolding due to hydrophobic/hydrophilic chains. Hydrophobic side chains are on the inside. Polar, charged chains are on the surface. Quaternary Finally considered proteins. Two or more polypeptides interacting. Protein Denaturation: ● No enzyme required ● loss of quaternary, tertiary, and secondary structures ● Polar amino acids dissolve very well in water; aqueous ● Nonpolar amino acids dissolve very well in membranes ● in response to change from heat, pH, or salt Heat: ● Heat breaks hydrogen bonds Salt: ● Na+ ● Cl pH: ● H+ add acid ● OH How do Rgroups vary? ● Size: a single hydrogen to a long chain or a bulky ring structure ● Charge: positive, negative, or neutral ● Polarity: ○ Partial charge on an atom ○ Result in unequal sharing of electrons (polar covalent bond) ○ example: hydroxyl group (OH) Collagen: ● Fibrous three helical polypeptides; triple helix ● Connective tissue, bone, tendons, and ligaments make up 40% of protein in the body ● Not involved with Alzheimer’s or Parkinson’s Carbohydrates: ● Glucose aldose (top)(C=O) ● Fructose ketose (middle)(C=O) ● complex sugarsdisaccharides ● Polysaccharides ● Six carbons, pentose, hexoses ● Linear to ring structure ● break glucose down ● carbon skeletons (points on ring structure) used to make amino acids, fatty acids ● disaccharides, polysaccharides ***Two glucose makes maltose ***Glucose and fructose make sucrose Starch: ● Polysaccharide ● Storage molecule ● Amylase breaks down starch ● Plant storage polysaccharide that can be eaten by humans and other animals Glycogen: ● How animals and humans store ● Granules in the liver and muscle cells ● Need to have access to glucose for a lot of functions ● Storage molecule ● Glucose monomers ● In liver and muscle cells because it is easily accessible
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