Unit 1  Terms:  Chemistry is the study of matter, it’s chemical and physical properties, the chemical and physical  changes it undergoes, and the energy changes that accompany those process.   Matter is anything that has mass and occupies space  Energy is the ability to do work to accomplish some change.   Notes:  States of matter:  Solids: particles are tightest together Not compressible, has a fixed volume and shape of  its own  Liquid: particles of a liquid are less tightly packed, not compressible, assumes the shape,  but not the volume of its container  Gas: particles are very separate highly compressible, assumes both the shape and the  volume of its container  The Scientific Process: Observation, Formulation of a question, Pattern recognition, developing  theories, experimentation, and summarizing information.   Chemical vs Physical:  A physical change produces a recognizable difference in the appearance of a substance without  causing any change it its composition or identity. This would be like water freezing to ice. It has  changed to a solid, but it’s still H2O. A chemical change is when a change in the chemical make-  up of the molecule takes place. An example of this would be when photosynthesis takes place in  a plant.  Parts of an Atom  An atom is the smallest building block of life, but it can be divided into a smaller portion. In  contains a positively charged proton in the nucleus (the nucleus is the center of the atom), the  neutrally charged neutron also in the nucleus, and then positively charged electrons outside of  the nucleus.     Electron Shells (and the periodic table)  Electronic configuration describes the arrangement of electrons in atoms. The periodic table is  helpful because it tells us a lot about the electronic configuration of atoms. Valance electrons are  the outermost electrons in an atom. The number of valance electrons in an atom corresponds to  the number of the group in which the atom is found on the periodic table. So for instance,  Sodium has one valence electron because it is in group 1. The first electron energy level is level  1, and it can hold two valance electrons. The next is energy level 2, and it holds 8 valence  electrons. The next is level three, and it holds 8 valance electrons. Etc etc. The periodic law gives  us two main rules:  Rule 1: The number of valence electrons in an atom equals the group (column) number for all  representative elements.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 1 of 26  Purchaser: jeng490@gwmail.gwu.edu Rule 2: The energy level (n=1,2, etc.) in which the valence electrons are located corresponds to  the period (row) in which the element may be found.   Related to this is the octet rule. This rule suggest that every element “wants” it’s valance energy  shell to be full, and it will try to “take” or “share” an electron from other atoms to get that full  valance shell. You should also know that it will take the path of least resistance to get there. (So  if it has a choice between gaining one electron, or losing seven, the atom will try to gain one)  When an atom takes an electron, there is a negative charge to that atom; when an atom losses an  electron, it has a positive charge. There is an attraction between these two atoms, and they bond  ionically.  Covalent bonding is a little more complicated. Let’s look at an example: Let’s look at  hydrogen. This has one valence electron. But in nature, you never find just one hydrogen atom.  Instead you find H2. So in the previous strategy we saw that one could steal it from the other.  But there is no reason that one would steal the electron from the other hydrogen. The better  solution is that the two hydrogen atoms “share” the electron. This is called covalent bonding. We  write this as a line. Like this H—H.  Element, Compounds and mixtures:  A pure substance only has one component, i.e water. It is made up of H20 molecules and nothing  else. An element is a pure substance that cannot be changed into a simpler form of matter by a  chemical reaction. To stick with the water example, hydrogen and oxygen are elements. A  compound is a substance resulting from the combination of two or more elements in a definite,  reproducible way. With the water again, H2O is a compound. A mixture is is a combination of  two or more pure substances in which each substance retains its own identity. (For those of you  with Friday on your brain, it is like Rum and Coke. You put them in the same cup and stir it up,  but it’s still Rum and Coke.)  A mixture can either be homogeneous which has a uniform mixture, or a heterogeneous mixture  which is non uniform. A homogeneous example is the rum in coke, which can also be called a  solution. Rocks in a sandbox are not a uniform mixture, and the mixture is therefore  heterogeneous.     Periodic Table:  How to read:  The atomic number is equal to the number of protons in the atom. The atomic mass is the  number of protons plus the number of neutrons.  Take a look at the following  a  zxc    The A is the mass number (which is the number of electrons plus the number of protons), the Z is  the atomic number (which is the number of protons in an atom), and the C is the charge of the  atom.  You can figure out the number of neutrons in an atom by subtracting the mass number minus the  number of electrons (This only works when the positive and negative charges cancel out).    History:  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 2 of 26  Purchaser: jeng490@gwmail.gwu.edu Dmitri Mendeleev made the periodic table. He came up with the periodic law that states: “The  elements if arranged according to their atomic weights show a distinct (periodicity (regular  variation) of their properties.” Chemical and physical properties of the elements correlate with  the electronic structure of the atom that makes up these elements. He ordered the elements in  order of increasing atomic numbers. A period is a horizontal row of elements in the periodic  table. Groups, or families, are columns of elements in the periodic table.   A metal is a substance whose atoms tend to lose electrons during chemical changes forming  positive ions. A nonmetal on the other hand, is a substance whose atoms may gain electrons,  forming negative ions. There is a boundary on the periodic table that is not metals or nonmetals.  These are called metalloids.   Trends in Atomic size  1. The energy level in which the valance electrons are found increases as we go down a  group on the periodic table. Therefore the size of atoms should increase from top to  bottom.  2. Atomic size decreases from left to right in the periodic table.   Positive ions are smaller than the parent atom. This is because they have more protons than  electrons; therefore the pull from the protons is now more effective in drawing the electrons in.   Negative ions are larger than the parent atom for the exact opposite reasons.     The energy required to remove an electron from an isolated atom is the ionization energy. (The  magnitude of this number tells us the ease of forming positive ions.) In other words, a large  ionization energy indicates that the atom becomes more stable as it becomes a positive ion.  The  magnitude of the ionization energy should correlate with the strength of the attractive force  between the nucleus and the outermost electron.   Periodic Trends for Ionization Energy  1) As we read down a group, the ionization energy decreases (this is because the size of the  atom is increasing, and thus the last electron is farther away from the positive pull of the  protons)  2) Reading across the period, the ionization energy increases (this is because the size of the  atom is decreasing, and thus the last electron is closes to the positive pull of the protons)    Electron affinity is the energy released when a single electron is added to an isolated atom. (In  other words, it is the measure of the ease of forming negative ions). A large electron affinity  indicates that the atom becomes more stable as it becomes a negative ion.    Formal Charge:  The Formal Charge of Molecule=The number of electrons the molecules starts with, minus the  number of bonds the molecule has, minus the number of unshared electrons    Resonance:  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 3 of 26  Purchaser: jeng490@gwmail.gwu.edu This is the idea that no single Lewis Dot Diagram can say exactly how a molecule looks because  it is always moving. Therefore we represent it like this:       Drawing Molecules (Straight from the Class Notes because this can be confusing):  I) Shape  a. Simplest Case  i. The concept is two points make a line, and so two atoms also would form  in a line.  1. H—H   ii. Diatomic Molecules are linear  b. Molecular Shape (Not that Simple)  i. VSEPR (Valance Shell Electron Pair Repulsion)  1. Valance Shell Electrons (We are only working with the valance  electrons)  2. Electron Pair: Electrons operate in pairs (or groups of pairs when it  comes to covalent bonding)  3. Repulsion  a. The idea that because electrons are all negative, they are  repelled away from each other and want to move as far  away as possible from the other electrons.   i. So if we have two bonds (or set of bonds) they  would be in a line, because they 180 degrees is as  far from each other as it gets. See below   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 4 of 26  Purchaser: jeng490@gwmail.gwu.edu   ii. With three bonds (or sets of bonds) the farthest they  can get from each other is in what we call a trigonal  planar model. In this shape, the electrons are 120  degrees away from each other    iii. It gets a little tricky when we have four bonds. In  real life, molecules are 3D. Now they do not stay on  one plane. Now they form a tetrahedral    iv. In our Lewis Dot diagrams it is important to point  out that it is shown in the picture below. The one  the is shaded darkly, is the one that is supposedly  coming out of the picture to you, and the other  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 5 of 26  Purchaser: jeng490@gwmail.gwu.edu lighter shaded one, is the one that is going away  from the picture.                   I) Unshared Electrons? (Shape Continued)   a. Electron pairs (lone pairs) also repel.   b. Example: NH3    c. NH3 has 3 bonds and 1 lone pair  i. They have eight all together in this Lewis diagram  1. Hydrogen has 1 valence electron  2. Nitrogen has 5 valance electrons  ii. They should all have full octets, which they do.   d. These are all at about 109.5 degrees (107.8)  e. The shape, though is named after the locations of atoms  i. Trigonal Pyramidal (See Picture )    f. Example: H20    i. Valence Electrons  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 6 of 26  Purchaser: jeng490@gwmail.gwu.edu 1. Hydrogen has 1 valence electron  2. Oxygen has 8 valence electrons  3. You can see in the lewis diagram that everyone has a full octet  ii. We name the shape not on where the electrons are, but rather where the  atoms are. So we get this:    iii. It’s called bent angular.   g. Another Example  i. O3     ii. This has 2 sets of bonds, and 1 lone pair   iii. As you can see you have many electrons, but you only have 3 atoms, so  once again you get bent angular.    iv. Electronegativity: a tug of war.   1. Ionic bonding is when you have two things that have very different  electronegativity and one element just overpowers the other, and it  takes an electron from the other element.   2. When you have Covalent bonding, this is when you have equal  electronegativity, and there is a “Stalemate” between the two  elements, then the electrons are shared between the two.   a. What if we had two atoms with different  electromagnativities, but not a drastic difference? This is  what happens in Polar Covalent.   b. That means that there is a more negative charge towards be  due to the negativity of the electrons  i. This is why we call it Polar covalent  h. Polar Bonds, Polar molecules  i. In Some molecules, the bonds are non-polar, so the molecule is non polar.  An examples is H2.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 7 of 26  Purchaser: jeng490@gwmail.gwu.edu   ii. Sometimes you have polar bonds, but they cancel out, so the molecule is  non-polar. An example is CO2    iii. In some molecules, polar bonds add up, so the molecule is polar  1. In H20, you have two dipoles, which do not cancel each other out.   2. In the picture below, the black arrow plus the black arrow equals  the red arrow.     Naming Molecules    It is also important to be able to write the correct formula when given the compound name. To  do this, we must be able to predict the charge of monatomic ions and remember the charge and  formula of polyatomic ions. Equally important, the relative number of positive and negative ions  in the unit must result in a net (compound) charge of zero. The compounds are electrically  neutral.   The steps for naming covalent compounds follow:  1) The names of the elements are written in the order in which they appear in the formula.  2) A prefix (which you can find in the table below) indicating the number of each kind of  atom found in the unit is placed before the name of the element.  3) If only one atom of a particular kind is present in the molecule, the prefix mono is usually  omitted from the first element  4) The stem of the name of the last element is used with eh suffix –ide.   5) The final vowel in a prefix is often dropped before a vowel in the stem name.    Prefix Number of Atoms  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 8 of 26  Purchaser: jeng490@gwmail.gwu.edu Mono 1  Di 2  Tri 3  Tetra 4  Penta 5  Hexa 6  Hepta 7  Oct 8  Nona 9  Deca 10      For instance, let’s look at how we would name N20. We would first put the prefix Di in front of  Nitrogen because there are two elements there. Then we would add –ide to the end of Oxygen.  Therefore this makes this molecule dinitrogyn Oxide.     We would name NO2, Nitrogyn Dioxide.     Unit 2: Organic Chemistry  Organic means the chemistry of carbon and its compounds. Carbon gets its own section of  chemistry because it forms covalent bonds that are strong even in long chains. They have four  bonds with single, double, and triple bonds, which gives these chains lots of variety. A  hydrocarbon contains only hydrogen and carbon. The simplest hydrocarbon molecule that is  possible is CH4.  This is part of a related group of compounds called alkanes, hydrocarbons that  contain only single bonds.    But before jumping in too far, one needs to know about line angle drawings.   1) There’s something called a line-angle drawings  a. These are useful because they are more simple  i. Rules  1. Every vertex represents a carbon  2. Since every carbon makes four bonds, we infer hydrogens to add  up to four.  (Stay with me, it gets clear)  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 9 of 26  Purchaser: jeng490@gwmail.gwu.edu 3. So when we see this, our brain should do some filling in. Below is  like a kind of a snapshot of what our brain should do.    a. Above is just three ways of showing the same thing.  b. The image below should offer some more examples.     c. Yeah that last one is tricky as hell. Basically because we have one bond, and then a  triple bond, there has to be a carbon, because one bond can’t just be bonded to three  bonds because there has to be an atom to hold those bonds together  Functional Groups:   Functional groups are groups of atoms that give a family of organic compounds its characteristic  chemical and physical properties. The professor has said we don’t need to memorize these, but  we should be familiar with them.    CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 10 of 26  Purchaser: jeng490@gwmail.gwu.edu     An Alkyl group is derived from an alkane by removing a hydrogen atom. The methyl group for  example, is derived from methane and the ethyl group from ethane.     Here are guidelines on how to go about naming different functional groups:  1. Naming Alkanes  d. Prefix for # of C’s, plus “ane”  e. But sometimes you have a branch coming out of your molecule.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 11 of 26  Purchaser: jeng490@gwmail.gwu.edu i. So here’s how you go about it. So you name the branch as prefix + “yl” and say  where it is. (Like if it is on the second carbon, then you put a two in front of it. )    1. If there are two ways of putting the number on it, you go with the  smallest number.   2. The last one is tricky for the exact same reason. BEWARE.  THEY GET TRICKY.       Alkenes-one or more carbon double bond  4. So this is the simplest Alkene   a. Alkenes have NO ROTATION. So is not the same as    b. Naming Alkenes  c. Prefix + “ene”  d. Identify where the double bond is.  i. So you put a number where the double bond is. Like  is 1-butene  e. Branches like alkanes  i.  is 3-methyl-1-penten   ii. See the branch is named the same away that alkynes were.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 12 of 26  Purchaser: jeng490@gwmail.gwu.edu b. Alkynes   i. They are hydrocarbons with triple bonds.   1. This means the bonds are 180 degrees   ii. Prefix + “yne”   c. Aromatics  i. Things like Benzene  1. This is the Lewis Structure of Benzene    2. But because we have alternating double and sing bonds. There is  resonance, so we can draw it like this    3. But to make it easier, we symbolize it like this.   ii. Aromatics are very stable because of their ring like structure.   2) Isomers   a. Ex:  i. How would you draw a Lewis structure for C4H10? So you draw this:    ii. Well yes, but you could also draw this:   iii. Both are correctly drawn. But they are not the same molecule.   b. Isomers are made of the same pieces, but they are connected differently  c. Isomers will share some properties, but differ in other  i. Probably same weight, but not the same burning points.    3) Chiral vs Achiral  a. Mirror images are sometimes the same, but not always  i. Chiral: When the mirror image is NOT the same as the original  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 13 of 26  Purchaser: jeng490@gwmail.gwu.edu   1. This one is not. You can’t get these two to match up just so.   2. If you have four different groups attached to a carbon tetrahedral,  they will always be chircal.   ii. Achiral: when the mirror image is the same as the original     1. Both of these are methane. It’s exactly the same.   b. Ex:   i. These two molecules are not the same. We know this because we know  that spearmint and caraway taste very different to the human tongue.   4) Conclusion of Today’s Lesson (which has been oddly slow)  a. To know how a molecule will interact with the body, you have to know what the  atoms are, how they are connected, and how the mirror images effect the body.     Unit 3: Polymers  What the hell is a polymer? : Polymers are large molecules consisting of a long chain of chains  of atoms covalently bonded together. A polymer molecule can contain thousands of atoms and  have a molar mass of over a million grams. Given their size, polymers are referred to as  macromolecules, that is, molecules of high molecular mass that have characteristic properties  because of their large size. Monomers are the small molecules used to synthesize the larger  polymeric chain. Each monomer is analogous to a link of the chain. In every day use, we call  many polymers plastics, either way, plastic or polymer, we are talking about a large molecule  that has been synthesized from smaller ones.   Polyethylene: A closer Look  Polyethylene has a wide variety of uses. For example, it is found in plastic milk jugs, detergent  containers, baggies, and packing materials. Yet, as we have seen in the previous section, all  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 14 of 26  Purchaser: jeng490@gwmail.gwu.edu polyethylene is made from the same starting material: H2C=CH2. How can this one monomer  form polymers that can be used in so many different ways?   The hydrogen bond in H2C=CH2 is not a covalent bond. Rather it Is an intermolecular attractive  force, that is, an attraction between two molecules resulting from the interactions of the electron  clouds and nuclei. These attractive forces are different from the covalent bonds that exist within  each molecule.   Each atom in the long polymeric chain contains its own electrons. But these electrons can be  attracted to the atoms on neighboring molecular chains, and the magnitude of the attraction  between strands of polyethylene is a direct result of the large number of atoms involved. The  intermolecular forces holding polyethylene together are called dispersion forces. These forces are  attractions between molecules that result from a distortion of the electron cloud that causes an  uneven distribution of the negative charge  A reaction you should know:  i. Condensation Reactions    1. If you were to take these two functional groups, you could make this, but a small  molecule is removed  2. So when two molecules get together to make one molecule, and water is a byproduct,  that is a condensation reaction    I) Intermolecular Interactions  a. There are different states of matter. Like in water, there is ice, water, and steam.  These are only physical transformations. But what is different, is how the atoms  are acting between each other  b. Facts:  i. Bonding happens within a molecule   ii. Intermolecular interactions are the forces between molecules  iii. The stronger the interaction, the more the molecules stick together  iv. Intermolecular interactions lead to thing (FILL IN)  c. Forces  i. Van der Waals (London) forces  a. The weakest force  b. Occurs between anything with electrons (therefore all  atoms/molecules)  c. More electrons=strong force   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 15 of 26  Purchaser: jeng490@gwmail.gwu.edu 2. So let’s look at this atom. What if all the molecules looked like  this?     a. Then you would have a little dipole (that is when one part  of the atom is more positive, and the other side is more  negative.)  3. But because electrons move all the time, so the dipole is going to  be constantly moving around. But wait! What if there were two  Neon atoms that looked like this?    a. Well there would be a slight attractive force between the  two.   b. In this case, there would be a repulsion force between the  two.   4. Over time, there is a slight attractive force between the electrons.  5. Because it is a weak force, the boiling points are pretty low on  these molecules  ii. Dipole-dipole  1. Next strongest intermolecular interaction  2. This requires that you have polar molecules     a. These atoms are polar, so when you have a bucket full of  these atoms, they will be attracted to each other  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 16 of 26  Purchaser: jeng490@gwmail.gwu.edu 3. Because there is more energy holding Dipole-dipole attractive  forces together, the boiling point is much higher.   iii. Hydrogen Bonding  1. Strongest intermolecular interactions  2. Needs 2 parts  a. A hydrogen covalently bound to a strongly electronegative  atom (ex: O, N)  b. A lone pair on another electronegative atom.     3. So we have these two water molecules, there is an attractive  interaction between the hydrogen donor part, and then another  attractive interaction between the donor receiver part.   4. One water molecule interacts with four other water molecules.  There is a really strong attraction between the molecules.   a. This is why it has such a high boiling point, and why little  tiny bugs can walk on water ( a strong surface tension)  1) Biopolymers  More Biopolymers-Proteins   a. Amino Acids  i. There are 20 different Amino Acids  ii. This is the basic structure of an amino acid    1. An amine  2. A carboxylic acid  3. And an R  a. An r is a shorthand way of saying some other carbonic  group  b. There are three basic “R”s or side chains  i. The first major class are hydrophobic side chains  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 17 of 26  Purchaser: jeng490@gwmail.gwu.edu 1. These don’t work well with water.  a. This is because this does not have  hydrogen bonding, or polar bonding  ii. Some are hydrogen bonding  iii. Some side chains are charged  1. Some are positively charged  some are  negatively charged  b. Polypeptides (proteins)  i. This picture shows how we can make a long chain of amino acids into a  chain to form a protein.     ii. Where we get variation on the proteins are on the side chains. (The red Rs)  1. Most proteins are around 100 amino acids long. So there are many  different formulas for proteins   c. Primary Structure  i. Basically there is a long chain of amino acids, but it has no function until  there is a shape  ii. Primary Structure is a sequence of a chain of amino acids   iii. But what starts giving form to the protein is when intermolecular reactions  cause the chains to take on shape.   d. Secondary Structure  i. This is when hydrogen bonding between amid group causes the primary  chain to take on some well defined local structure.  1. The picture below shows how chains happen to have hydrogen  donors, and acceptors next to each other, and therefore hydrogen  bond in a sheet formation    CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 18 of 26  Purchaser: jeng490@gwmail.gwu.edu 2. The next picture shows how the chains will hydrogen bond to itself  because the hydrogen bond donor is close to the hydrogen bond  receiver is close together.    e. Tertiary Structure  i. In this, the secondary structure comes together in a 3D shape that is held  together by intermolecular forces from the sides of the Polypeptide chain.     1. This happens when the side chains interact among themselves  using intermolecular forces like hydrogen bonding, or polar  bonding  2. Every type of protein shapes itself in its way  f. Quaternary Structure  i. This is when a protein is made up of more than one strand, and  intermolecular forces act, and another level of structure is formed.   ii. Like in the picture below, you can see that four chains have bonded  together to give this protein Quaternary Structure.     2) Protein Function  a. There are three main functions proteins provide  i. Structural-Proteins make up the shape and strength of the body.   ii. Transport-Proteins carry certain things to different parts of the body  1. Ex: Some proteins get oxygen to different parts of the body.   2. Ex: Some proteins acts as “doors” to cells   iii. Catalysis-These are enzymes    Unit Four: Drugs  Pharmaceuticals are anything that alters biological function  Drugs are chemicals: collections of atoms bound together to form molecules. A medicine- a pill,  capsule, cream, or linctus, for example, contains drug molecules mixed together with inactive  substances such as sugars and starches to make the tablet east to handle.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 19 of 26  Purchaser: jeng490@gwmail.gwu.edu Most drug molecules contain between 10 and 100 atoms and the manner in which these can be  combined is astronomical. The science of pharmacology is the science not only of trying to  understand the basis of disease, but also of trying to design different configurations of these  atoms in order to alleviate specific symptoms of a disease or, ideally, to cure the illness all  together  The body is made up of millions of small units called cells which can be seen only under a  microscope. Cells are collected together to form larger units with a particular function. These  large units are the tissues and organs such as the hearts, kidneys, liver, pancreas and brain. Each  organ produces several hormones which enter the bloodstream and travel around the body to  affect other organs. Speaking of which, hormones have very specific functions.   The activities of many organs, including their production of hormones are controlled by nerves.  Nerves affect the organs by secreting chemicals called neurotransmitters (because they transmit  information between nerves or from nerves to the organs. One feature of hormones and  neurotransmitters is that their effects must be specific, producing effects only on those organs or  cells where their action is needed and not everywhere in the body.   Each cell has a membranes. These are special groups of molecules known as receptors, because  they detect or receive the molecules of hormones in the blood stream. Usually a hormone  interacts with its own specific receptor or receptor family. This specificity of hormone-receptor  interaction is sometimes likened to a lock and key, since each hormone usually fits only one type  of receptor in just the same way that a key first only one lock. This concept is the underlying  thought behind making drugs. If we can create a drug that will only act on one type of receptor to  create the desired effect, we have a successful drug.   Almost every organ is connected to nerves which have two basic functions. Some of the nerves  are sensory, which means that they detect, or sense, changes in an organ’s blood supply,  chemical environment, position, and temperature and signal that information to the brain. Some  of the nerves are motors and carry information from the brain to the organs, causing muscles to  contract or glands to secret hormones. Nerves communicate with heave other and with organs by  releasing hormone-like chemicals called neurotransmitters.   There are several types of receptors  Norepinephrine Receptors- The nerves that we have no conscious control over release  norephinephrine which can react on two families of receptors known as alpha and beta receptors.  When norepinephrine acts on alpha receptors it makes the walls of blood vessels contract,  leading to an increase of blood pressure. Beta receptors relax blood vessels, but they also make  the heart beat more strongly and more rapidly, increasing the amount of sugar in the blood, and  reduce activity of the intestine. Drugs that block these receptors are known as Alpha or Beta  blockers.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 20 of 26  Purchaser: jeng490@gwmail.gwu.edu Acetylcholine receptors- Another group of nerves, known as parasympathetic nerves, releases  acetylcholine onto glands and involuntary muscles. Activation of the receptors this works on  stimulates the secretion of saliva when we eat, allows the eye to adjust when we read of view  nearby objects, and maintains activity of the intestine and stomach. Drugs that block this receptor  are used to treat Irritable Bowel Syndrome.  The above receptors are also the receptors that activate our voluntary or skeletal muscles. In this  case, the receptors can also be stimulated by nicotine.   It should be pointed out that some drugs, like steroids, bind into a molecule in the cell wall,  which then transports them into the interior of the cell. There, they combine with their receptor  molecule and the combination of steroid plus receptor then moves into the nucleaus of the cell  where it can modify the genetic machinery of the cell.   A drug which has the same effect as a natural hormone or transmitter by activating the same  receptor, is called an agonist at that receptor.   Some drugs act on enzymes. There are lots of chemical reactions in the body, many of them are  carried out by special molecules in the body called enzymes. Enzymes are large proteins which  assist and encourage chemical reactions without becoming changed themselves. They are the  biological equals of catalysts in chemistry. Some drugs act by inhibiting enzymes, preventing  them from carrying out their normal function. Just as drugs targeted at receptors need to be  specific for the receptors of only one hormone or transmitter, this drugs acting on enzymes  should ideally affect only one of the many thousands of different types in order to minimize side-  effects.   There are several other drug targets. They can act on pores in the walls of cells called channels.   An emerging science is called genomics. Genomics involves identifying and studying the genetic  differences and changes which are responsible for diseases. If a gene defect is found, the next  stage of research is to identify the function of that gene, which might code for a receptor or  enzyme. This knowledge in turn should allow chemist to design new drugs to act on the receptor  or enzyme and correct the disease-causing defect.   Function Follows Form:  Most of the body’s messes are conveyed not by electrical impulses, but through chemical  processes. The chemical messengers produced by the body’s endocrine glands are called  hormones. The wide range or aspirin’s therapeutic properties, as well as its side effects, is clear  evidence that the drug is involved in several chemical communication systems. Enzymes are  proteins that act as biochemical catalysts, influencing the rates of chemical reactions.  Cyclooxygenases catalyze the synthesis of a series of hormone-like compounds called  prostaglandins from arachidonic acid.  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 21 of 26  Purchaser: jeng490@gwmail.gwu.edu Prostagladins cause a variety of effects. They produce fever and swelling, increasing sensitivity  of pain receptors, inhibit blood vessel dilation, regulate the production of acid and mucus in the  stomach, and assist kidney functions. By preventing prostaglandin production, aspirin reduces  fever and swelling. It also suppresses pain receptors and so functions as a painkiller. Because the  benzene ring conveys high fat solubility, aspirin is also taken up into cell membranes. In certain  specialized cells, the drug blocks the transmission of chemical signals that trigger inflammation.  This process also appears to be related to aspirin’s effectiveness as a pain reliever.  Because it is a specific chemical compound, aspirin is aspirin, regardless of its brand. Although  all aspirin molecules are identical, not all aspirin tablets are the same. The products are mixtures  of various components. The differences in formulation can influence the rate of uptake of the  drug and hence, how fast it acts, and the extent of stomach irritation it produces. Aspirin also  decomposes with time, and the smell; of vinegar can signify that such as process has begun.  Fortunately, none of this poses a significant threat to health, and the benefits of aspirin far  outweigh the risks for the great majority of people.    Drug Testing and Approval:  The Feed, Drug, and Cosmetic Act of 1938 and its amended version in 1951, and 1962 defined  prescription drugs as ones that could be habit-forming, toxic, or unsafe for use except under  medical supervision. Virtually everything else is available for sale over the counter (without a  prescription). From discovery to approval, the development of new drugs takes, on average  nearly 8-10 years and about $500 million-over three times the cost of decade ago. The odds of  getting a candidate drug from identification to approval are 10 in 10,000. For every 10,000 trail  compounds that begin the process, 20 make it to the level of animal studies, half that many get  clearance for use in clinical testing with humans, and finally 1 gets FDA approval. Perhaps the  most controversial toxicity testing involves the determination of the lethal dose-50 (LD50), the  minimum dose that kills 50% of the test animals.   Large-scale clinical trials are desirable because a large pool will more likely include a wide  range of subjects. Variety is important because the drug in question may have markedly different  effects on the young and the old, on men and women, on pregnant or lactating women, on  infants, nursing infants, and unborn fetuses, and on persons suffering from diabetes, poor  circulation, kidney problems, high blood pressure, heart conditions or a host of other maladies.   Once a drug receives the FDA’s permission, a drug can be sold in the United States.  Nevertheless, it still remains under scrutiny, monitored through reports from physicians. The  lengthy process for drug testing and approval is not without controversy. Bringing a new drug to  marked is incredibly expensive and the numbers of new drug approvals are not keeping pace  with rising research and development costs. For example, in hospital a single dose of tirofiban, a  medication that dramatically increases the likelihood of surviving a heart attack, has a price tag  of $1100. Such prices have driven the costs of medical care and medical insurance. In some  cases, the costs of the protracted drug approval process may be human lives.  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 22 of 26  Purchaser: jeng490@gwmail.gwu.edu  When there is nothing to lose, people are willing to take great risks, possibility taking  imperfectly tested drugs. To respond, the FDA has tried to respond.. Ten years ago, and FDA  review for a new drug required nearly three years, whereas today it is less than a year. A new  “fast-track” system has been instituted for priority drugs-those that address life-threatening  ailments or new drug therapies for conditions that had no such therapies. The fast-track policy  promises to have priotiry drugs, if found to be acceptable, approved within six months of  application.   There is a significant financial disincentive for a pharmaceutical company to invest heavily in  developing a drug that will be used by only a small fraction of the population: such medications  are called “orphan drugs.”   Drugs of Abuse  According to the 2004 Substance Abuse and Mental Health Services Administration survey an  estimated 19.1 million Americans or 7. 9% of the population age 12 or older was current illicit  drug users. Current means use of an illicit drug during the month prior to the survey interview.  Some of the following are interesting facts:  • Marijuana is the most commonly used illicit drug. Of the 14.6 million users of marijuana  in 2004, about one third, or 4.8 million persons, used it on 20 or more days in the past  month.  • 2 million persons were current cocaine users 467,000 of whom used crack. Hallucinogens  were used by 929,000 persons, including 450,000 users of ecstasy. There were an  estimated 166,000 current heroin users.   • An estimated 121 million persons or 2.5% of the population age 12 or older, were current  users of psychotherapeutic drugs taken nonmedically. An estimated 4.4 million used pain  relievers, 1.6 million used tranquilizers. 1.2 million used stimulants, and .3 million used  sedatives.   • An estimated 121 million Americans age 12 or older reported being current drinkers of  alcohol . About 55 million participated in binge drinking, and 16.7 million were heavy  drinkers (binge drinking 5 or more days in the past month.   • 29.2% of the population 12 years or older reported current use of a tobacco product in  2002.   The first known record of marijuana use dates back to the time of the Chinese Emperor Shen  Nung who prescribed use of the plant for the treatment of malaria, gas pains, and  absentmindedness. George Washington kept a field of hemp at Mt. Vernon, and it is believed  that he used the plant for both rope and medicine. Extracts of marijuana were employed by  physicians in the early 1800s for a tonic and euphoriant. But in 1937, the Marijuana Tax Act  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 23 of 26  Purchaser: jeng490@gwmail.gwu.edu prohibited its use as an intoxicant and its medical use was regulated as national concern of its use  emerged. The Marijuana Tax Act required anyone producing, distributing, or using marijuana for  medical practice to register and pay a tax that effectively prohibited nonmedical use of the drug.  The current legal status of marijuana was established in 1970 with the passage of the Controlled  Substance Act.   When Marijuana smoke is inhabled, THC rapidly passes from the lugs into the bloodstream,  which carries the chemical to organs throughout the body, including the brain. In the brain, THC  connects to specific sites called cannabinoid receptors on nerve cells and influences the activity  of those cells. Some brain areas have many cannabinoid receptors; other have few or none. Many  cannabinoid receptors are found in the parts of the brain that influence pleasure, memory,  thought, concentration, sensory and time perception, and coordinated movement. THC leaves the  blood rapidly through metabolism and uptake into the tissues. The chemical may remain stored  in body fat for long periods; research has indicated that a single dose can take up to 30 days for  complete elimination The short-term effects of marijuana use can include problems with memory  and learning, distorted perception, difficulty in the thinking and problem solving, loss of  coordination, decreased blood pressure, and increased heart rate. The current debate over the  medical use of marijuana is basically a debate over the value of its medicinal properties relative  to the risk posed by its use. The debate is colored by complex moral and social judgments that  underlie current drug control policy in the United States.  The institute of Medicine, a part of the National Academy of Sciences, published a review in  1999 that found marijuana to be “moderately well suited for particular conditions, such as  chemotherapy-induced nausea and vomiting, and AIDS wasting.” By 2005, ten states had laws  that permit physicians to prescribe marijuana for medical purposes. In 2006, Rhode Island  became the 11th state to pass a medical marijuana law for the seriously ill. The significance of  this was that Rhode Island was the first state to move on the issue since the U.S Supreme Court  ruled in June 2006 that patients who use the drug can still be prosecuted under federal law.   Morphine, oxycodone, hydrocodone (found in Vicodin, Lortab, and Lorcet), and codeine belong  to a class of drugs known as opiates. These drugs bind to a chemical receptor called mu, that  interrupts the transmission of pain in the spinal cord. Opiates also stimulate areas of the brain  involved in pleasure, called the reward, or endorphin, pathways. Opiates stimulate the release of  higher levels of dopamine, strengthening rewards signals, and producing intense euphoria.     Unit 5: Allergies and Asthma  An allergic reactions is a set of bodily changes occurring when some people are exposed to  agents in the environment to which they have become sensitive. The term comes from the Greek  words allo-means other and ergon-meaning work.   CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 24 of 26  Purchaser: jeng490@gwmail.gwu.edu On exposure to an antigen some of the white cells in the blood begin to produce antibodies to the  antigen. Antibodies are large  molecules which combine with the antigen and trigger the allergic  reaction. If it reappears, the antibody combines with the antigen and triggers the formation of  millions of other antibodies to the same antigen. The antigen-antibody complex also triggers the  release of chemicals called mediators within a few minutes, so that an allergic response appears  very quickly after exposure to antigen.   Mediators and the Allergic Reaction  The white blood cells are part of the immune system. The main result of a person’s being  exposed to an antigen, or an antigen-antibody complex is that the white blood cells, and similar  cells called mast cells called mast cells preset in the tissues, release mediators which include  histamine and leukotriens. Mediators are responsible for the signs of allergy:  1) They irritate the membranes lining the nose. They also dilate blood vessels in the nose and  increase the leakiness of the walls of blood vessels. The result is some fluid being pushed out of  the blood into the tissue lining the nose, causing congestion or a runny nose.   2) Mediators also relax blood vessels and activate sensory nerves in the skin.   3) They increase the secretion of mucus by gland cells in the airways and contract the muscle  cells in the airways. These two effects produce the wheezing, coughing, and shortness of breath  seen in asthma.   4) The fever and feeling of tiredness associated with allergies, colds, and influenza are due to the  effects of these mediators on the brain.    Why do allergies develop?  More than 1 child in 10 will show signs of asthma before the age of 10 years, although the  condition will disappear again in about half of these children. One possible reason for the  increasing incidence of allergies is that chemical pollutants in the atmosphere and diet are acting  as antigens to increase the sensitivity of the immune system as a whole so that more people show  allergic reactions such as asthma in response to previously harmless stimuli. Another popular  idea is that allergies result from the accidental juxtaposition of harmless and dangerous stimuli.  For example, a person’s immune system may be very active in order to deal with an infection  such as a cold or influenza. If at the same time, that person is exposed to other molecules, such as  those found on cat hairs, the activated immune system may overreact to those normally innocent  molecules and produce antibodies to these too. The stage is then set for an allergic reaction when  the person is exposed only to the cat hairs.   Drug Treatment  Decongestants- The runny nose and secretion of tears in colds and hay fever can be treated by  drugs which prevent or oppose the effects of the mediators on blood vessels. One group of drugs  contracts blood vessels by activating the alpha-receptors which normally respond to epinephrine  and norepinephrine. Some of these drugs act directly on the receptors to mimic the effect of  CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 25 of 26  Purchaser: jeng490@gwmail.gwu.edu epinephrine. Others act on the sympathetic nerves, causing them to release their stores of  norepinephrine which then act on the receptors. The contraction of blood vessels produced by  these drugs opposes the immune system’s attempts to dilate the vessels  Antihistamines-The second group of decongestants are the antihistamines. Histamine is one of  the chemicals released into the bloodstream by white blood cells and mast cells when antibodies  meet foreign antigens. In the nose, histamine relaxes the muscle cells in the small blood vessels.  With the easier movement of fluid across the vessel wall means that water is forced out of the  blood into the nose, leading to a runny nose, irritation of the nasal lining, and sneezing. The  antihistamine drugs prevent all these changes.       CHEM 004 (Hietbrink) Midterm Review  Packet for exam on 3/4/09  Page 26 of 26  Purchaser: jeng490@gwmail.gwu.edu