Chemistry 1027A/B Chapter Notes - Chapter 17: Monoamine Oxidase, Messenger Rna, Tricyclic Antidepressant

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Published on 20 Apr 2013
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Chemistry 1027A/B
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Chemistry 1027B
Chapter 17: Chemistry and Medicine
Medicines, Prescription Drugs, and Diseases: The Top Tens
Over-the-counter drugs: those that can be bought in any supermarket or drugstore
Prescription drugs: cannot be purchased without instructions from a physician
o A substance is available only by prescription if:
It has potentially dangerous side effects
It should bused only by people with specific medical problems
It treats a condition so serious that a person with that condition should be under a doctor’s care
o The most prescribed drug in 2008 was Lipitor, which lowers blood cholesterol and stabilizes plaque while
acting as an anti-inflammatory
A drug is classified as one or the other by the Food and Drug Administration (FDA)
All drugs have a trade name and a generic name
o Trade name: the brand name, or the name used by the drug manufacturer
o Generic name: a drug’s generally accepted common chemical name
Once the patent protection on a drug has expired, it can be manufactured and marketed competitively by
many companies and prescribed by its generic name
Often, prescriptions written by the generic name are cheaper to fill
The dramatic decrease in infectious diseases since 1900 can be attributed in large measure to the development of
antibiotics
Also AIDS continues to be a very serious health issue, AIDS deaths in the U.S. have dropped dramatically due to
intensive educational programs regarding AIDS prevention and the development of drugs that, although unable to
cure AIDS, can prolong life expectancy dramatically
o The cost of these drugs has, at least in part, prevented their use on a worldwide basis
Drugs for Infectious Diseases
Infectious disease: a disease caused by microorganisms
Antibiotic: a substance produced by a microorganism that inhibits the growth of other microorganisms
o A person falls victim to an infectious disease when invading microorganisms multiply faster than the body’s
immune system can destroy them
o Help the immune system by either destroying invaders or preventing their multiplication
Penicillins
Pathogenic: capable of causing disease
Amoxicillin, the most-prescribed antibiotic, is a penicillin
All penicillins kill growing bacteria by preventing normal development of their cell walls
Unlike our cells and those of other animals, bacteria rely in a rigid cell wall
The rigidity is maintained by cross-linking bonds between peptide chains
Penicillins inhibit the enzyme that forms these cross links and prevent the reaction from occurring, causing the cell
to burst
Other Classes of Antibiotics
The cephalospirins are similar in structure to the penicillins and also act by disrupting cell wall synthesis
o They are widely used in hospitals because of their low toxicity and broad range of antibacterial activity
o All cephalosporins have the same general structure in which R1 is often a hydrogen, and R2 and R3 are
substituents with several functional groups
Other kinds of antibiotics attack bacteria in different ways from the penicillins and cephalosporins
o Many interfere with the synthesis or functioning of bacteria DNA
Tetracyclines and erythromycin inhibit bacterial protein synthesis
Rifampin inhibits RNA synthesis from DNA
After more than a half-century of use, many antibiotics are not nearly as effective as they once were
AIDS: A Viral Disease
Other than vaccination, there are very few knows ways to combat viral diseases
o This is because they are essentially chemical parasites they take over the DNA of human cells and put it to
work for their own reproduction
o It is difficult to attack the cells reproducing the virus without also attacking the host’s own cells
HIV is a retrovirus: the virus enzyme carries out RNA-directed synthesis of DNA rather than the usual DNA-
directed synthesis of RNA
o It consists of an outer double lipid layer surrounding a matrix containing proteins, an enzyme called reverse
transcriptase, and RNA
Attack of HIV on a T cell of the immune system:
o The virus enters the lymphocyte and produced its own DNA
o The DNA enters the lymphocyte nucleus, where it combines with the lymphocyte’s DNA
o Through the cell’s normal processing, DNA is transcribed to messenger RNA and, back outside the nucleus,
the viral RNA provides the template for the production of proteins that assemble into new virus particles
Protease inhibitors taking in combination with older AIDS drugs dramatically lowers the concentration of the
virus in the patients’ blood, often to below detectable levels
o A combination of drugs overcomes the major problem with single-drug therapy if a few virus particles are
left alive by a drug treatment, the virus can very quickly adapt by converting to a drug-resistant from
Protease inhibitors act by inhibiting a protease enzyme
o By fitting into the active site of the enzyme, the inhibitors prevent the enzyme from functioning
o Because this enzyme cuts a long protein chain into smaller proteins essential to survival of the HIV virus,
halting its action kills the virus
The new drug combination is not yet a cure it is extremely expensive, it is unavailable in many developing
countries, and it can have unpleasant side effects
Steroid Hormones
Hormones are produced by glands and secreted directly into the blood
They serve as chemical messengers, regulating biological processes by interacting with receptors that are
sometimes distant from where they are secreted
Hormones are chemically diverge but are mostly proteins or steroids
Neurotransmitters
Hormones and neurotransmitter have in common their roles as chemical messengers within the body
Neurotransmitters carry nerve impulses from one nerve to the next or to the location where a response to the
message will occur
The body has a number of neurotransmitters, each it with its own distinctive molecular receptors and functions
Norepinepherine, Serotonin, and Antidepressive Drugs
Norepinepherine and serotonin are neurotransmitters with receptors throughout the brain
o Norepinepherine helps to control the fine coordination of body movement and balance, alertness, and
emotion; it also affects mood, dreaming, and the sense of satisfaction
o Serotonin is involved in temperature and blood pressure regulation, pain perception, and mood
o Serotonin and norepinepherine appear to work together to control the sleeping and waking cycle
The normal cycle of neurotransmitter action at nerve synapses, the gaps between nerve endings, is as follows:
o The neurotransmitter is released from the neuron
o The neurotransmitter crosses the synapse to interact with the receptor
o The neurotransmitter is inactivated, either by re-uptake by the neuron it came from or by conversion to an
inactive form by an enzyme
The biochemistry of mental depression is not fully understood, but a deficiency of norepinepherine and serotonin
(and possibly dopamine as well) almost certainly plays a role
o Evidence is provided by the manner in which three classes of influence the action of these neurotransmitters
The tricyclic antidepressants prevent inactivation of neurotransmitters by preventing their e-uptake by
neurons, which increases the concentration of the neurotransmitter in the synapse
The monoamine oxidase inhibitors diminish the action of monoamine oxidase, which is the enzyme that
inactivated norepinepherine and serotonin
Selective serotonin inhibitors prevents the recapture of serotonin by neurons that release it (and has
become the choice for treating serious clinical depression)
o For each of these three classes of drugs the major mechanism of action is to increase the concentration of
neurotransmitters at synapse
Dopamine
Produced in several areas of the brain, where it helps to integrate finer muscular movement as well as o control
memory and emotion
Dopamine does not cross the blood-brain barrier and thus cannot be administered as a drug
o L-Dopa is able to cross the barrier and can then be converted to dopamine in the brain
Used to alleviate Parkinson’s symptoms
Dopamine has also been identified as the neurotransmitter that produces the feelings of well-being and reward
associated with drug addiction
Drugs that block dopamine receptors have been used to treat schizophrenia (a complex condition not solely
attributed to dopamine activity)
Epinephrine and the Fight-or-Flight Response
Epinephrine, also known as adrenaline, is both a neurotransmitter in the brain and a hormone released from the
adrenal gland
Its sudden discharge when we are frightened produces the fight-or-flight response, which includes increased blood
pressure, dilation of blood vessels, widening of the pupils, and erection of the hair
Because of its widespread and rapid effects, epinephrine has a number of medical uses, notably in crisis situations
such as cardiac arrest, dangerously low blood pressure, acute asthma, and anaphylactic shock
The Dose Makes the Poison
The amount of chemical substance that enters the body is known as a dose
Whether a dose of a given substance is poisonous or not depends on the size of the dose
For a given individual, age, gender, eight, and general state of health also play a role in the effect of a given dose
Doses of medications and poisons are customarily expressed as milligrams per kilogram of body weight (mg/kg)
A quantitative measure of toxicity is obtained by administering various doses of substances to be tested to
laboratory animals
o The dose found to be lethal in 50% of a large number of test animals under controlled conditions is called the
LD50 (lethal dose 50%) and is usually reported in milligrams of the substance per kilogram of body weight
o Since species differences can produce different LD50 values for a given poison, defining risk to human beings
based on animal data is difficult, but it is generally safe to assume that a chemical with a low LD50 value for
several species will also be quite toxic to humans
Painkillers of all Kinds
Analgesics: drugs that relieve pain; some are illegal drugs, some are prescription drugs, and some are OTC drugs
Opium and its Relatives
Chemically, opium is an alkaloid an organic compound that contains nitrogen, is a base, and is produced by
plants
About 10% of crude opium is morphine, which is medically valuable as a strong painkiller able to produce
sedation and loss of consciousness, is primarily responsible for the effects of opium
The term opioid is now applied to all compounds with morphine-like activity
Heroin, the diacetate ester of morphine, does not occur in nature but can be synthesized from morphine

Document Summary

Medicines, prescription drugs, and diseases: the top tens. Over-the-counter drugs: those that can be bought in any supermarket or drugstore. Prescription drugs: cannot be purchased without instructions from a physician: a substance is available only by prescription if: It should bused only by people with specific medical problems. It treats a condition so serious that a person with that condition should be under a doctor"s care: the most prescribed drug in 2008 was lipitor, which lowers blood cholesterol and stabilizes plaque while acting as an anti-inflammatory. A drug is classified as one or the other by the food and drug administration (fda) All drugs have a trade name and a generic name: trade name: the brand name, or the name used by the drug manufacturer, generic name: a drug"s generally accepted common chemical name. Once the patent protection on a drug has expired, it can be manufactured and marketed competitively by many companies and prescribed by its generic name.