Transcript Option D. Medicine and Drugs

Option D: Medicines and Drugs
Created by K. Slater
Resources include: ChemActive, IB Chemistry Option D Revision
Guide, R.M. Capanema Mansur, L. Scheffler
D1 Pharmaceutical products
D.1.1 List the effects of medicines and
drugs on the functioning of the body.
 D.1.2 Outline the stages involved in the
research, development and testing of new
pharmaceutical products.
 D.1.3 Describe the different methods of
administering drugs.
 D.1.4 Discuss the terms therapeutic
window, tolerance and side-effects.

D.1.1 List the effects of medicines and drugs
on the functioning of the body.
Generally, a medicine or drug is any
chemical that does one or more of the
following:
◦ Alters the physiological state, including
consciousness, activity level or coordination
◦ Alters incoming sensory sensations
◦ Alters mood or emotions

Sometimes it is difficult to determine whether a drug
has any medicinal value
D.1.1 List the effects of medicines and drugs
on the functioning of the body.
 Placebo effect:
◦ A pharmacologically inert substance (often a
sugar pill) produces a significant reaction
because the patient expects, desires, or was
told it would happen
◦ Used as a control in clinical trials
◦ Highlights the body’s natural healing powers
Questions:
D.1.2 Outline the stages involved in the research,
development and testing of new pharmaceutical
products.

Several stages in development of drugs include:
◦
◦
◦
◦
◦
Isolation or chemical synthesis of the product
Laboratory studies
Animal testing
Clinical testing
Approval by the FDA for market
D.1.2 Outline the stages involved in the research,
development and testing of new pharmaceutical
products.

Development of a new drug is a very costly,
lengthy process controlled by the
government:
◦ In 1970, 3620 drugs were tested. 16 came on the
market at an average cost of $20 million
◦ Only 1 in 2000 drugs eventually make it to the market
◦ Phase I: Initial clinical trials on volunteers after the
drug has proven safe when given to animals
◦ Phase II: Thorough clinical investigation to eliminate
investigator bias
◦ Phase III: Extended clinical evaluation
D.1.2 Outline the stages involved in the research,
development and testing of new pharmaceutical
products.

All drugs that are approved for market must be clinically
tested multiple times:

A) Most clinical tests are done on volunteers.
B) Neither the researcher know in advance who is
receiving the therapeutic medicine and who is receiving a
placebo
C) Half receives the medicine and the other the placebo



The initial trial will establish possible side effects and
drug’s safety.
D.1.3 Describe the different methods of
administering drugs.



Drugs must reach blood stream to be
transported to critical tissues.
The method of administration determines
rate at which the drug is absorbed in the
blood.
Five common points of entry:
1.
2.
3.
4.
5.
Oral
Inhalation
Topical
Injection
Anal
D.1.3 Describe the different methods of
administering drugs.
Injection methods:
◦ Subcutaneous
Under the skin
◦ Intramuscular
In the muscle
◦ Intravenous
Directly in the vein
Questions:
D.1.4 Discuss the terms therapeutic
window, tolerance and side-effects.
Therapeutic window: Relates the therapeutic
effects of a drug to its toxic effects
Tests are performed on all pharmaceuticals to
establish their toxicity
◦ LD50 is the dose (in mg of substance per kg of body
mass) that is lethal to to 50% of laboratory animals
◦ LD = Lethal Dose
◦ The lower the LD50, the more toxic the substance
 Lowest LD50 rating known as of yet: the
concentrated form of botulism toxin (BoTox) –
most toxic substance known LD50 of roughly
0.005-0.05 µg/kg
◦ http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LD50.html
D.1.4 Discuss the terms therapeutic
window, tolerance and side-effects.
LD50 (g/kg)
Aspirin
1.5
Nicotine
0.23
Caffeine
0.13
Botulin
3 x 10-11
Question
D.1.4 Discuss the terms therapeutic
window, tolerance and side-effects.

Tolerance: Over time the body adapts
the presence of a drug
1.The person receiving the drug needs ever
larger doses to achieve the original effect
2.Tolerance results in increased risks of
dependency/addiction
3.Increased risks of toxic levels
4.Possibility of immunity in anti-bacterials
D.1.4 Discuss the terms therapeutic
window, tolerance and side-effects.

Side-effects: Contraindications are additional
and often undesirable effects that result from
the use of a particular drug to treat a particular
condition
◦ Side effects are somewhat relative depending on the
reason the drug is prescribed
◦ The prescribing physician must weigh the benefits
from the use of a drug against the undesirable side
effects when determining a suitable level of risk
◦ The level of risk that is acceptable is related to the
severity and the degree to which the condition is life
threatening
◦ Examples: chemotherapy, pain killers, etc.
Thalidomide: An Example of Improper
Drug Approval
Developed in Germany in the 1953.
 Used as a tranquilizer (19571962).
 Prescribed to combat morning
sickness in the early months of
pregnancy.
 Marketed widely in Europe but
never approved by the FDA in the
USA.
 Caused major birth defects in
ABOUT 10,000 children whose
mothers had taken thalidomide.

17
Thalidomide
Thalidomide has two
optical isomers, one
of which is a
powerful teratogen.
Chiral
Carbon
18
Thalidomide
Thalidomide is both a tranquilizer and a teratogen
It is sometimes used to
treat some symptoms
of Hansen’s disease.
(Leprosy)
19
Review
1.
2.
3.
4.
When defining drugs what are three ways
in which drugs affect the body?
Explain the following: Therapeutic index,
tolerance, the placebo effect, effective
dose, lethal dose.
Outline the steps in bringing a drug to
market.
What happened with the drug,
thalidomide, that resulted in a major drug
catastrophe?
20
D2 Antacids

D.2.1 State and explain how excess acidity
in the stomach can be reduced by the use
of different bases.
D.2.1 State and explain how excess acidity in the
stomach can be reduced by the use of different bases.
Food is digested in the stomach that contains
gastric juices, HCl with a pH value of about 2.
 Antacids are compounds that are used to
neutralize excess stomach acid(HCl)
 Most antacids are weak inorganic bases:

◦
◦
◦
◦
◦
CaCO3
NaHCO3
Mg(OH)2
Al(OH)3
MgO and Mg(OH)2 (Milk of Magnesia)
D.2.1 State and explain how excess acidity in the
stomach can be reduced by the use of different bases.
Neutralization reactions between HCl & …
Aluminium hydroxide
 Magnesium hydroxide
 Sodium hydrogen carbonate

WRITE ‘EM OUT!!!
D.2.1 State and explain how excess acidity in the stomach
can be reduced by the use of different bases.
Question:
 State and explain which would be more
effective as an antacid, 1.0 mol of
magnesium hydroxide or 1.0 mol of
aluminium hydroxide. Support your answer
with balanced equations.
(3)
Answer:
 aluminium hydroxide neutralizes more acid
/ more HCl / moreH+ ions
/ contains more OH− ions;
 Al(OH)3 + 3H+ → Al3+ + 3H2O;
Mg(OH)2 + 2H+ → Mg2+ + 2H2O;
 Accept equations with HCl.
3
D.2.1 State and explain how excess acidity in the
stomach can be reduced by the use of different bases.
Antacids are often combined with
alginates and antifoaming agents
 Aliginates float on the stomach contents
to form a neutralizing layer preventing
heart burn
 Antifoaming agents such as dimethicone
prevent the formation of gases and
reduce flatulence

D3 Analgesics
D.3.1 Describe and explain the different ways
that analgesics prevent pain.
 D.3.2 Describe the use of derivatives of salicylic
acid as mild analgesics, and compare the
advantages and disadvantages of using aspirin
and paracetamol (acetaminophen).
 D.3.3 Compare the structures of morphine,
codeine and diamorphine (heroin, a semisynthetic opiate).
 D.3.4 Discuss the advantages and disadvantages
of using morphine and its derivatives as strong
analgesics.

D.3.1 Describe and explain the different ways that
analgesics prevent pain.
Analgesics: substances that reduce pain without
the aid of sleep
 Mild: Intercept the pain stimulus at the source
of injury or interfere with production of
substances (like prostaglandins) that cause pain,
swelling or fever.

◦ Aspirin and Paracetamol

Strong: Temporarily bond with receptor sites in
the brain, preventing the transmission of pain
impulses without depressing the CNS.
◦ Morphine
D.3.1 Describe and explain the different ways that
analgesics prevent pain. – Aspirin

Salicylic acid was in wide use as a
pain killer and antipyretic but it
irritates & damages the mouth,
esophagus and stomach
membranes
 2 hydroxybenzoic acid

In 1899, Bayer introduced the
ethanoate ester of salicylic acid:
 2 acetoxybenzoic acid or acetyl
salicylic acid
D.3.1 Describe and explain the different ways that
analgesics prevent pain. – Paracetamol (acetaminophen)





Less side effects than aspirin.
May cause kidney, liver damage
Functional group: amide
Preferred in the USA
Overdose can cause brain damage to liver
and kidneys
D.3.1 Describe and explain the different ways that
analgesics prevent pain. – Opiates
Strong analgesics are given to relieve
severe pain caused by injury, surgery, heart
attack or chronic diseases.
 Opiates go straight to the brain, find
chemical receptors that receive pain
messages and bind with (and blocking) the
receptors, which stops the transmission of
pain
 Problems: Tolerance can develop  OD 
death

D.3.2 Describe the use of derivatives of salicylic acid as mild
analgesics, and compare the advantages and disadvantages of using
aspirin and paracetamol (acetaminophen).
Aspirin
 Pros:
◦ Preventing recurrence of heart attacks &
strokes (prevents blood clotting)

Cons:
◦ Ulceration & stomach bleeding
◦ Allergic reactions
◦ Reye’s syndrome in children – a potentially
fatal liver and brain disorder
◦ Overdose can lead to acidosis (low blood pH)
D.3.2 Describe the use of derivatives of salicylic acid as mild
analgesics, and compare the advantages and disadvantages of using
aspirin and paracetamol (acetaminophen).
Paracetamol (acetaminophen)
 Pros:
◦ Very safe in the correct dose
◦ Safe for children – no side effects

Cons:
◦ In rare cases, can cause blood disorders and
kidney damage
◦ OD can lead to serious liver damage, brain
damage and even death
D.3.3 Compare the structures of morphine, codeine and
diamorphine (heroin, a semi-synthetic opiate).

Morphine, codeine (found in opium poppy) and
heroin all have same basic structure:
Structure of morphine
D.3.3 Compare the structures of morphine, codeine and
diamorphine (heroin, a semi-synthetic opiate).
D.3.3 Compare the structures of morphine, codeine and
diamorphine (heroin, a semi-synthetic opiate).
Morphine has an alcohol (hydroxyl group)
 In codeine, the hydroxyl group is replaced
by a methyl group.
 Heroin has 2 acetyl groups (ethanoate)

D.3.4 Discuss the advantages and disadvantages of using
morphine and its derivatives as strong analgesics.

Advantages:
◦ Extremely strong, relieve severe pain caused
by injury, surgery, heart attack or chronic
diseases
◦ Treatment of diarrhea (produces
constipation)
◦ Cough suppressant
D.3.4 Discuss the advantages and disadvantages of using
morphine and its derivatives as strong analgesics.

Disadvantages – short-term:
◦
◦
◦
◦

Euphoria
Depress nervous system (slow breathing)
Nausea & vomiting
May lead to coma / death
Disadvantages – long-term:
◦ Constipation, poor eating habits
◦ Increased tolerance  addiction
 Social problems, such as theft & prostitution
 Risk of AIDS, hepatitis, etc. from sharing needles
 Cross-tolerance: increases tolerance for other opiates
D4 Depressants





D.4.1 Describe the effects of depressants.
D.4.2 Discuss the social and physiological effects
of the use and abuse of ethanol.
D.4.3 Describe and explain the techniques used
for the detection of ethanol in the breath, the
blood and urine.
D.4.4 Describe the synergistic effects of ethanol
with other drugs.
D.4.5 Identify other commonly used
depressants and describe their structures.
D.4.1 Describe the effects of depressants.

Depressants: a group of drugs that, according to
dosage, reduce anxiety, produce calm and
induce sleep
◦ Often described as antidepressants b/c they relieve
depression
◦ Examples: alcohol, barbituates (phenobarbital) and
benodiazepines
Low doses: may exert little or no effect
 Moderate doses: may induce sedation (soothing,
reduction of anxiety)
 High doses: may induce sleep
 Extremely high doses: may cause death

D.4.2 Discuss the social and physiological effects of
the use and abuse of ethanol.
Physiological Effects
Social and Economic
Consequences
Reduction in inhibitions
Violent behaviour (like the
British spelling? ) to family
or strangers
Increase in car accidents
Short-term reduction in
reaction speed
Short-term hangover
Absenteeism from work
Long-term liver (and much
other) damage
Cost of intensive medical
care
D.4.2 Discuss the social and physiological effects of
the use and abuse of ethanol.
Short-term health effects
(Effect depends on body
mass and concentration of
alcohol in the blood)






Reduces anxiety and
inhibitions
Increases confidence &
sociability
Dilates small blood vessels 
warmth
Impairs attention, judgment,
and control
Violent or aggressive behavior
Loss of motor function
Long-term health effects

Alcoholism is caused by an
inability to reduce alcohol intake
◦ Withdrawal symptoms: nausea,
sweating, anxiety, hypertension or
delirium tremens (shaking)
◦ Tolerance








Cirrhosis (scarring) and cancer
of the liver (the major
detoxification organ)
Heart disease
Hypertension
Strokes
Gastritis
Ulcers
Depression
Miscarriage / birth defects
D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
Multiple methods are used to detect alcohol levels
1.
2.
3.
Breathalyser by potassium dichromate (VI)
Blood or urine analysis by chromatography
Absorption of infrared radiation or fuel cell in an
intoximeter
D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
1.
Breathalyser by potassium dichromate (VI)

Subject breathes into an analyzer containing an oxidizing agent
and a detector
Potassium dichromate (K2CrO4) is the oxidizing agent
Oxidizes ethanol to ethanoic acid
This is an oxidation-reduction reaction that involves an
electron transfer
Cr+6 (orange) is reduced into Cr+3 (green) --- KNOW THIS
This electron transfer generates an electric current which can
be detected by the machine





D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
2.





Blood or urine analysis by chromatography
More precise than breathalyzer
Uses a stationary phase (non-volatile liquid or solid support) and
a mobile phase (inert gas, like N2)
Breath components (CO2, H2O, and alcohol vapor) are injected
into the machine and partitioned (divided) between the
stationary and mobile phases
Components exit at different intervals (each substance has a
different affinity and bond strength for the two phases, and thus
move through at different rates)
Components are detected

Retention time for each component is measured (time taken
for each component to pass through the column)

Blood alcohol’s retention time is compared to the retention
time for a standard ethanol sample
D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
3.
Absorption of infrared radiation or fuel
cell in the intoximeter

IR light does not promote electrons to higher levels, but
does provide enough energy to make molecules “vibrate”
◦
Vibrational motion depends on the mass of the molecule and
the types of bonds present
IR spectrum therefore depends on types of molecules
present (“molecular fingerprint”)
Scale is based on wavenumber (1/wavelength)
Police use intoximeter (IR spectrometer) to confirm
breathalyzer test



◦
◦
◦
IR radiation is passed through breath sample
C-H group in alcohol absorbs a certain frequency of IR light
% transmittance of the C-H frequency is determined,
indicating amount of alcohol present
D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
Question:

A modern method for accurately determining the
amount of alcohol in breath uses an intoximeter.
Explain how an intoximeter works.
(3)
Answer:

sample of breath passed into infrared
spectrometer; ethanol in breath
absorbs because of OH group; machine
compares breath with air/reference
sample with no breath
D.4.4 Describe the synergistic effects of ethanol
with other drugs.


Synergistic effect: the combination of the two
drugs may be more harmful than either drug
alone
When alcohol interacts with other drugs:
◦ Can produce coma or death when combined with sleeping
pills or barbiturates
◦ Can cause stomach bleeding with aspirin
◦ Can extend and enhance the “high” when mixed with
cocaine
 Also causes severe vasoconstriction (narrowing of blood
vessels leading to a rise in blood pressure) and cardiac
arrhythmia (irregular heart beat)
◦ Can inhibit breakdown of other drugs
D.4.5 Identify other commonly used depressants
and describe their structures.
Diazepam (Valium): relieves anxiety and
tension, muscle relaxer
 Nitrazepam (Mogadon): hypnotic drug used
to induce sleep
 Fluoxetine hydrochloride (Prozac): used to
treat mental depression by increasing
serotonin activity (a neurotransmitter)

D.4.5 Identify other commonly used depressants
and describe their structures.
Fluoxetine
hydrochloride
(Prozac)
Questions:
Questions:
D5 Stimulants
D.5.1 List the physiological effects of
stimulants.
 D.5.2 Compare amphetamines and
epinephrine (adrenaline).
 D.5.3 Discuss the short- and long-term
effects of nicotine consumption.
 D.5.4 Describe the effects of caffeine and
compare its structure with that of
nicotine.

D.5.1 List the physiological effects of
stimulants.

Stimulants: Molecules that increase
alertness and give greater sensitivity to
external stimuli
◦ Mental processes may speed up
◦ May create feelings of elation or possibly
anxiety
D.5.2 Compare amphetamines and
epinephrine (adrenaline).
Adrenaline is a naturally occurring
hormone and stimulant – fight or flight
 Amphetamines mimic the effects of
epinephrine (adrenaline) and are known
as sympathomimetic drugs

D.5.2 Compare amphetamines and
epinephrine (adrenaline).

Amphetamines and epinephrine (adrenaline) are
chemically similar in that both derive from the
phenylethylamine structure (i.e. a benzene ring
with a 2-C chain and an amine group at the end)
D.5.2 Compare amphetamines and
epinephrine (adrenaline).
◦ Amphetamine is a
primary amine,
having a –NH2
group
D.5.3 Discuss the short- and long-term
effects of nicotine consumption.

Short-term:
◦
◦
◦
◦
◦

Increased heart rate
Increased blood pressure
Reduction in urine output
Decrease in reflex times
Stimulating effects
Long-term:
◦ Increased risk of heart disease
◦ Coronary thrombosis
◦ Peptic ulcers
D.5.3 Discuss the short- and long-term
effects of nicotine consumption.
Addictive properties of nicotine
 Further risks associated with smoking
tobacco, such as lung cancer

D.5.4 Describe the effects of caffeine and
compare its structure with that of nicotine.

Caffeine is a respiratory stimulant
◦ When consumed in large amounts it can
cause anxiety, irritability and sleeplessness
◦ It is a weak diuretic (promotes the formation
of urine)
D.5.4 Describe the effects of caffeine and
compare its structure with that of nicotine.

Both caffeine and nicotine contain a
tertiary amine group (a nitrogen atom
bonded to three carbons)
D.4.3 Describe and explain the techniques used for the
detection of ethanol in the breath, the blood and urine.
Question:
Describe two similarities in their structures, not
including the presence of double bonds, methyl
groups and nitrogen atoms.

Answer:

both contain
six-membered ring;
five-membered ring;
(tertiary) amine group;
N- has methyl group attached; 2 max
◦
Award [1] each for any two.

Methylamphetamine (also known as methamphetamine or
“speed”) and caffeine are stimulants with the following
structures.
(a)
(i) On the structure for methylamphetamine above, draw
a ring around the amine group. (1)
(ii)Determine whether both amine groups in caffeine are primary,
secondary or tertiary. (1)
(b)
Caffeine contains the group . State the general name for
this functional group. (1)
(Total 3 marks)

(a) (i)
◦ The ring must circle the N atom to gain
the mark.
◦ (ii)
tertiary

(b) amide / N-methylamide (accept
peptide)
D6 Antibacterials
D.6.1 Outline the historical development
of penicillins.
 D.6.2 Explain how penicillins work and
discuss the effects of modifying the sidechain.
 D.6.3 Discuss and explain the importance
of patient compliance and the effect of
penicillin overprescription.

D.6.1 Outline the historical
development of penicillins.
Antibacterial: a destructive to or
inhibiting the growth of bacteria
 Penicillin: any of several antibiotics of
low toxicity, produced naturally by molds
of Penicillium

D.6.1 Outline the historical
development of penicillins.
Alexander Fleming – a name to know
A bacteriologist, studied an antibacterial agent present
in tears and nasal mucus, as well as in egg whites (called
lysozyme) – in the 1920s
 Left a pile of used culture plates containing a growth of
a Staphylococcus bacterium
 A rare stain of fungus called Penicillium notate entered
through a window and landed on one of the plates
 A month later the fungus multiplied and inhibited the
growth of the surrounding Staphylococcus bacteria
 Ultimately, Fleming found that Penicillium
produces “penicillin” when its food resources are
limited & that it inhibits the growth of a wide
range of bacteria

D.6.1 Outline the historical
development of penicillins.
Howard Florey – another name to know
Ernst Chain – aaaand yet another name to know
 Florey continued research on lysozyme (the
antibacterial agent in egg whites) – in the 1920s & 1930s
 Chain (Florey’s student) showed that lysozyme attcks
the cell walls of bacteria  disintegration – 1937
 Chain (& 2 other scientists) improved the method of
isolating penicillin, improving its purity – 1938
 Chain was known for producing large quantities
of penicillin and conducting medical trials
 In 1945, Fleming, Florey & Chain were jointly awarded
the Nobel Prize in Physiology or Medicine
D.6.2 Explain how penicillins work and discuss the
effects of modifying the side-chain.
Penicillins work by interfering with the
chemicals that bacteria need to form
normal cell walls
 Modifying the side-chain results in
penicillins that are more resistent to the
penicillinase enzyme


Penicillins differ only in their type of side chain
◦ Penicillins function by interfering with the cross-links
that connect separate layers of the bacterial cell wall
 Cell wall is weakened and the bacterial cell bursts,
killing the bacteria
 Humans do not have cell walls and are thus unaffected
by penicillins
Mode of Action of Penicillin



They work by
interfering with the
enzymes that
bacteria need to
make normal cell
walls.
These enzymes can
become resistant.
As the cell swells,
the osmotic pressure
causes the wall to
disintegrate.
Benzylpenicillin
D.6.2 Explain how penicillins work and discuss the
effects of modifying the side-chain.
The origin penicillin notation mold was found to
produce a mixture of different penicillin's that
are called G, X, F and K.
 The most useful is Penicillin G because it has a
high effectiveness and a higher yield from the
fermentation process.
 Attempts have been made to modify the natural
penicillins chemically to vary the R group 3 new
Penicillin's were created: S, O, and V

D.6.3 Discuss and explain the importance of patient
compliance and the effect of penicillin overprescription.
Penicillin quickly became widely used as
antibiotic against a variety of bacteria
 Some history:

◦ During World War II, penicillins helped to rid of
infected wounds (the biggest wartime killer)
◦ Also used to treat infected transmitted
infections (STI’s) that were common in soldiers
D.6.3 Discuss and explain the importance of patient
compliance and the effect of penicillin overprescription.
Drug companies began mass producing
penicillin in 1943  Penicillin-resistant bacteria
 Bacteria can become resistant to penicillin (and
other antibiotics) because of overprescription
 Problem: If people take penicillin for a minor
bacterial infection than their immune system
would be able to deal with it, they are increasing
the chances of resistant strain emerging

D.6.3 Discuss and explain the importance of patient
compliance and the effect of penicillin overprescription.



When the non-resistant bacteria
are destroyed, the small numbers of
resistant forms will be able to
multiply due to an absence of
competition
A process of natural selection that
occurred in the bacterial
population
Similar reasoning can also be
applied to people who do need to
take antibiotics, but do not
complete their course of treatment
D.6.3 Discuss and explain the importance of patient
compliance and the effect of penicillin overprescription.

Example: Tuberculosis (TB) Treatment
◦ This takes 6-12 months of antibiotics to
rid of the bacteria
◦ TB resistance to penicillin and antibiotics is
growing since the process takes so long
◦ This could be considered an
overprescription
◦ It gives time for bacteria to build up
resistance
D.6.3 Discuss and explain the importance of patient
compliance and the effect of penicillin overprescription.


Antibiotics have been widely used in the livestock
industry to treat sick animals and to promote growth
Other drugs prescribed to livestock include hormones
to fatten and build up bulk weight and to reduce stress
D7 Antivirals
D.7.1 State how viruses differ from
bacteria.
 D.7.2 Describe the different ways in
which antiviral drugs work.
 D.7.3 Discuss the difficulties associated
with solving the AIDS problem.

D.7.1 State how viruses differ from bacteria.
Bacteria
Viruses
Individual cell (has the
machinery to do all it needs to
survive itself)
Acellular (don’t have
organelles & can’t survive
without a host)
Reproduces on its own
Requires a living host to
reproduce
Circular DNA
DNA or RNA in a capsid
Use & obtain energy /
metabolize on their own
Uses & obtains energy / from its
host
Bigger
Smaller
Grows & develops on its own
Cannot grow or develop
Viruses
How big is it? http://www.cellsalive.com/howbig.htm
 How viruses invade…
http://www.youtube.com/watch?v=Rpj0emEGShQ

Various Viruses
How Viruses Invade
D.7.2 Describe the different ways in which
antiviral drugs work.

Antiviral drugs may work by:
◦ altering the cell’s genetic material so the virus
cannot use it to multiply
◦ OR preventing the viruses from multiplying by
blocking enzyme activity within the host cell
D.7.2 Describe the different ways in which
antiviral drugs work.
Three possible approaches to killing a virus:
1. The Trojan Horse
2. Retrovirus Inhibitors
3. Blunting the scissors
D.7.2 Describe the different ways in which
antiviral drugs work.
1.



The Trojan Horse
Viruses uses host’s DNA-polymerase to
replicate viral DNA
Some antiviral drugs are structurally
similar to viral DNA and codes for the
replication process to stop
This is a challenge because the drug has
to be “activated” by a viral enzyme
D.7.2 Describe the different ways in which
antiviral drugs work.
2.




Retrovirus Inhibitors
A retrovirus (such as AIDS) contains RNA
rather than DNA
Normally, when retroviruses inject their RNA
into host cells, they use an enzyme, reversetranscriptase, to convert their RNA into viral
DNA in the cell
Retrovirus inhibitors work by inhibiting the
reverse-transcriptase enzyme and preventing
the formation of viral DNA
Example: AZT (Azidothymadine) is the best
known anti-AIDS drug
D.7.2 Describe the different ways in which
antiviral drugs work.
3.



Blunting the scissors
When new baby viruses are created in their
host cells, they need to escape so they can
infect other cells
They are able to do this by using an enzyme
(neuraminidase) which cuts open the host cell
wall, sort of like a pair of scissors
If we introduce an inhibitor molecule (making
it so they can’t make those cuts), then the
viruses permanently stay inside of the cell,
rendering itself harmless (since it can’t
replicate)
D.7.3 Discuss the difficulties associated with
solving the AIDS problem.


Specific proteins on the HIV virus bind to a receptor
protein on white blood cells called T cells
Effective treatment with antiviral drugs is difficult (as is
vaccine development) since:
◦
◦
◦
◦


Viruses are simple & replicate quickly
Viruses can mutate quickly & “learn” to cope with the drugs
Viral metabolism is linked closely with the host cell
Killing the virus could actually be easy if you didn’t care about
making sure the host lives :/
Therefore, pharmaceutical chemists focus on the
selective toxicity that allows the drug to work
AZT (Azidothymadine) is the best known antiHIV/AIDS drug
D.7.3 Discuss the difficulties associated with
solving the AIDS problem.
Other factors

◦
◦
Cost: it’s expensive
Societal & cultural:




95% of HIV positive people live in developing countries
Less than 8% who need retroviral therapy actually receive it
AIDS stigma… leads to a fear of discrimination and/or
violence, which can prevent many people from getting
tested or
Thus, prevention becomes a key aim in trying
to prevent the spread of / controlling AIDS