IB SL Chemistry Revision Paper 3: Medicine and Drugs
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Define a medicine
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A substance that improves health (has a therapeutic effect)
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Define a drug
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A chemical that affects the way the body works
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In a breathalyzer, state what is looked for in absorption. Why?
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It looks for the absorption of C-H bonds, rather than O-H because, although OH is the most prominent functional group of an alcohol, OH bonds are also present in water vapour which will be breathed out regardless of whether the person has been drinking or not
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Outline the placebo effect
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This is when a patient believes to be taking a certain drug, but in fact is just taking a sugar pill. The patient is unaware of this, and this has shown the therapeutic and healing effects even though the drug is pharmacologically intert (in double blind trials, neither the doctor nor the patient know whether the drug is a placebo or not)
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What does the placebo effect trigger?
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Opiate system - the body's own natural painkiller
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State the name of a drug and the dangerous effect it can have when taken with ethanol
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Aspirin - increased risk of stomach ulcers/bleeding Sleeping Pills - heavy sedation/coma
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Outline why it can be dangerous to drink ethanol when taking other drugs
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Has a synergistic effect with other drugs/can change the effectiveness of the drug
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Define the term 'therapeutic window'
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range of a drug's concentration in the blood between its therapeutic level and toxic level
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Define the term 'therapeutic effect'
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the intended physiological effect
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Define the term 'side effect'
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unintended physiological effect
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Define the term 'dosing regimen'
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amount of drug and frequency of administration for each dose
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Define the term 'tolerance'
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repeated doses of a drug result in a smaller physiological effect
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Define the term 'addiction'
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a dependence on a drug and feelings of withdrawal symptoms when the drug is taken away
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Explain why viral infections (e.g. AIDS) are more difficult to treat than bacterial infections
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-viruses mutate quickly so adapt to the drug -bacteria are more complex and thus can be targeted in more ways -different types of bacteria can often be targeted with common antibacterials, whereas each kind of virus tends to require a special drug -bacteria can be treated without attacking the host cell, whereas it is very difficult to attack a virus without attacking the host cell
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State the differences between the structures of morphine and diamorphine
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Diamorphine contains 2 esters Morphine contains 2 hydroxyl groups
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State all the functional groups in morphine
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Hydroxyl group Alkene Tertiary Amine Benzene Ring Ether
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Outline the differences between bacteria and viruses
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Bacteria: -larger than viruses -have a cytoplasm and cell wall -have more complex DNA -mutate slower than viruses -bacteria are self-reproducing (do not need host cell to reproduce) Viruses: -smaller than bacteria -only consist of genetic material -have much simpler DNA
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Describe ways in which antiviral drugs work
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-block the enzyme activity of the virus, which prevents viruses from multiplying -alter cells genetic material so that virus cannot use it to multiply -prevent viruses from entering cell
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How do mild analgesics work?
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by preventing the release of prostaglandins at the source of pain
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How do strong analgesics work?
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block the transmission of pain signals between brain cells without depressing the CNS and alter perception of pain (also temporarily bonds to receptor sites in the brain)
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Discuss advantages and disadvantages of using morphine and other opiates for pain relief
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Adv: -relieve stronger pain -intravenous (work faster than a drug) -wide therapeutic window Disadv: -could create an addition/dependence -lack of self control/dangerous behaviour -kidney/renal failure -tolerance increases --> increased risk of overdose
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State four common depressants
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-alcohol -nitrazepam -diazepam -fluoxetine hydrochloride
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Describe the effects of moderate doses of depressants on patients
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-relieving depression -calmness/relaxed muscles -reduces heart rate
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State some advantages and disadvantages of aspirin
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Adv: -antipyretic (reduces risk of fever) -reduces pain -cures inflammation -reduces ability of blood clotting -reduces risk of colon cancer Disadv: -irritates stomach (stomach ulcers/bleeding) -could be allergic (asthmatics) -Reye's syndrome in children (liver/brain disorder)
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State some advantages and disadvantages of paracetamol
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Adv: -one of the safest analgesics -does not usually irritate stomach -few side effects (as long as dosage is not exceeded) -allergic reactions are rare Disadv: -may cause blood disorders -does not reduce inflammation -is not antipyretic (does not reduce fever) -overdose can cause serious liver damage/brain damage/death
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State the ways in which drugs can be administered
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-parenterally (injections that can be intravenous/intramuscular/subcutaneous) -skin patches -orally -suppositories -eye or ear drops -inhaled
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State the name of the functional group present in diamorphine but not morphine
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ketone
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Describe the negative effects of caffeine
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-anxiety -irritability -sleeplessness -increased urine output (diuretic) -trembling -increased heart rate
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Describe the positive effects of caffeine (short term)
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-enhancement of mental ability -alertness -ability to concentrate
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Name two functional groups present in caffeine
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-tertiary amide -secondary amine
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Which functional group is common to both caffeine and nicotine?
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tertiary amine
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What is the importance of the therapeutic window on a drug?
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-if the concentration is too high, it may have harmful side effects -if the concentration is too low, it may be ineffective -a small therapeutic window increases the risk of an -overdose -for minor ailments a larger window is desirable
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Identify one effect of a drug which must be determined during clinical trials
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lethal dose/effective dose
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What is an advantage and disadvantage of taking drugs orally?
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Adv: easily taken/convenient Disadv: slow effect/stomach acid may react with drug
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Why is fluoxetine hydrochloride more soluble than nitrazepam and diazepam?
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salt has ionic bonds which can form polar bonds with water/hydrogen bonding with water
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Name 2 diseases causes by bacteria
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-salmonella -cholera
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Name 2 diseases caused by viruses
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-AIDS -influenza
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What was the main contribution of Florey and Chain to the development of Penicillin?
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-successfully isolated the penicillin -developed techniques to purify the penicillin -shows that penicillin is harmless/effective on mice -grew strains of penicillin in large amounts
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Describe some misuses of antibiotics which have led to bacteria becoming resistant
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-patients not finishing the course -the use of antibiotics in animal feed -overprescription
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Explain the meaning of the term 'sympathomimetic'
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-mimics the action of epinephrine/adrenaline -stimulate the sympathetic nervous system
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Describe the chance event that led to Fleming's discovery of penicillin
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left a petri dish containing bacteria and upon his return, noticed that mould had inhibited bacterial growth
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How does penicillin work?
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inhibits the development of cross-links in the bacterial cell walls, which weakens the walls and causes the bacteria to rupture/burst
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Why is it necessary to continue to develop new forms of penicillin with modified side chains?
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-bacteria become resistant to penicillin -produce the enzyme penicillinase
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Briefly outline the process for drug testing/design
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1) identify/extract the leading compounds that are shown to have biological activity 2) analogues of leading compounds are made and tested through combinatorial chemistry and high thorough-put screening 3)testing on animals to determine the lethal dose and effective dose 4)testing on humans -50-100 healthy volunteers -200-400 patients -3000+ patients (half given placebo)
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What was the Thalidomide disaster?
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-it was marked as a sedative/anti-inflammatory -given to pregnant mothers for morning sickness -found to have negative effects; babies born with birth defects (e.g. missing/malformed limbs)
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What is the role of antacids?
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neutralise excess stomach acids (they are usually weakly basic compounds)
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What are the common antacid ingredients?
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-aluminium hydroxide Al(OH)3 --> alkali -magnesium hydroxide Mg(OH)2 --> alkali -sodium hydrogencarbonate NaHCO3 --> base -calcium carbonate CaCO3 --> base
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What is the function of an antacid and an alginate?
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produce a neutralising later to prevent stomach acid from rising into the oesophagus (prevents heartburn)
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What is the function of an antacid and an anti-foaming agent?
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reduces amount of CO2 formed by the bases in antacids (reduces flatulence/bloating) e.g. dimethicone
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Name a mild analgesic
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paracetamol/aspirin
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Name a strong analgesic
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morphine/codeine/diamorphine (heroin)
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Describe how morphine is turned into heroin
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-through esterification reactions -both OH groups are converted into esters (ethanoate groups) by a reaction with ethanoic acid -the loss of polar OH groups means the heroin is less polar and therefore more lipid-soluble/fat-soluble -this enables it to cross the blood-brain barrier quickly, which is why it is faster acting than other opiod drugs
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State some advantages of codeine/morphine/diamorphine
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-suppress coughing -euphoria/feelings of happiness --> could be negative -can suppress stronger pain than paracetamol/aspirin -relieves anxiety
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State some disadvantages of codeine/morphine/diamorphine
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-causes constipation -loss of libido -weight variation -addiction possibility -lack of self control -kidney/renal failure -increased tolerance --> risk of overdose
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What is used to break an addiction to strong analgesics/opiods?
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methadone --> taken orally and reduces craving
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How do depressants work?
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act on the brain and CNS can change communication between brain cells by altering the concentration and activity of neurotransmitters
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What are depressants called?
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antidepressants (they relieve depression)
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What are the effects of low/moderate doses of depressants?
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-calmness -relief from anxiety -relaxed muscles
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What are the effects of high doses of depressants?
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-slurred speech -staggering gait -altered perception -sleep induced
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What are the effects of extremely highs doses of depressants?
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-respiratory depression -coma -death
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What are the short term effects of ethanol?
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-loss of self-restraint -loss of balance -violent behaviour (could be long term too) -risk-taking behaviour -dehydration due to increased urine output
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What are the long term effects of ethanol?
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-dependence/alcoholism -liver disease/cirrhosis/cancer -coronary heart disease -high blood pressure -fetal alcohol syndrome -brain damage
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Name some synergistic effects of ethanol
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-aspirin: increased bleeding of stomach lining -other depressants: heavy sedation -tobacco: increased risk of cancers -other drugs: can interfere with their effectiveness
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Describe the main features of breathalyser for ethanol
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-crystals of potassium dichromate (VI) are used to oxidise the ethanol to ethanal (aldehyde) and ethanoic acid (carboxylic acid) -the crystals change colour from orange to green -extent of colour is determined by a photocell which is not very accurate
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What is an intoximeter?
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a device which uses infrared spectroscopy to identify the CH bonds in ethanol (they don't use OH since they are present in water vapour)
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How does a fuel cell work?
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-converts the energy released when oxidation occurs into a detectable electric voltage -this can be used to measure ethanol concentration very accurately
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How is ethanol analysed in the blood/urine?
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-gas-liquid chromatography -the mobile phase: blood/urine is vaporized and injected into a stream of inert gas -the stationary phase: it is done over the surface of a non-volatile liquid -ethanol gas moves at a different rate to the other components of the vapour (each leaves the column after its retention time) -a peak at the retention time corresponding to ethanol confirms its presence
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Name some other depressants apart from ethanol
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benzodiazepines (diazepam/nitrazepam) - treats anxiety disorders/insomnia fluoxetine hydrochloride - treats eating/panic disorders
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What is the function of stimulants?
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increase brain activity/mental alertness alters levels of neurotransmitters
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State some effects of stimulants
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-facilitates breathing by relaxing air passages (used for infections e.g. bronchitis) -reduces appetite (treatment for obesity) -palpitations/tremors -restlessness/sleeplessness (if used in large amount) -hallucinations (if used in large amount) -fits (if used in large amount)
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State the different functional group between adrenaline and amphetamine
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adrenaline: secondary amine amphetamine: primary amine
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What do amphetamines and adrenaline (epinephrine) derive from?
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phenylethylamines (C8H11N)
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What is another name for a benzene ring?
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phenyl
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Name some stimulants
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epinephrine (adrenaline) amphetamines caffeine nicotine
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Name some sympathomimetic drugs
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epinephrine (adrenaline) amphetamines
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What is the function of adrenaline?
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to enable the body to cope with demands imposed by pain/fear/shock
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What is the function of amphetamines?
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increase mental alertness/physical energy
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State some short term effects of nicotine consumption
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-increases concentration -helps counter fatigue -increases heart rate/blood pressure -decreases urine output
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State some long term effects of nicotine consumption
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-high blood pressure -risk of heart disease (angina) -coronary thrombosis -increases levels of fatty acids
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State some negatives of nicotine consumption
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-increased risk of lung diseases -adverse effects on pregnancy -dependence/addiction
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What is the function of caffeine?
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reduce physical fatigue and restore alertness
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What kind of stimulant is caffeine?
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respiratory stimulant (increases rate of energy release within cells/intensifies effects of adrenaline)
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Compare the structures of nicotine and caffeine
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Similar: both have tertiary amine and alkene Different: caffeine has tertiary amide and secondary amine Solubility: Caffeine is water soluble and lipid soluble Nicotine is lipid soluble
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What is the main cause of AIDS?
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HIV - failure of immune system
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How does HIV work?
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-infects red blood cells in immune system by binding to receptor cells on their surface and penetrating the cell -the DNA of the HIV integrates into the cell's own DNA and replicates with it when the cell divides -viral particles are produced within the host cell and released in large numbers when the cell dies
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What kind of virus is HIV?
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a retrovirus - it has RNA instead of DNA
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Difficulties in treating HIV/AIDS
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1) destroys white blood cells - the very cells which should be DEFENDING the body 2) difficult to target it without damaging the host cells 3) mutates rapidly 4) virus often lies dormant - so immune system has nothing to respond to 5) medicines are expensive/need specialised medicines for each virus
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Name an effective antiviral drug
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amantadine
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What is the structure of penicillin?
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4 membered ring that consists of a nitrogen atom and 3 carbon atoms
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State a disadvantage of penicillin
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it is broken down by stomach acid and must be injected into blood
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What is the enzyme produced by bacteria that are resistant to penicillin?
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penicillinase ( an enzyme which can open penicillin's four membered ring and render it inactive)
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List some ways to stop antibiotic resistance
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1) develop different forms of penicillin with MODIFIED SIDE CHAINS that can withstand the penicillinase 2) control/restrict the use of antibiotics - reduce over-prescription 3) educate patients and ensure they finish the full course of treatment
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State 2 reasons why vaccines for HIV have failed
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1) variable nature of virus within cells 2) immune system responds too system
