Mrs. Sherien Ibrahim
IGCSE - Biology
A drug
Is a substance
that taken into
the body that
modifies or
affects chemical
reactions in the
body.
• Drug used in medical care, or to relieve mild pain, are
very helpful to us. However, some people misuse drugs,
so that they cause harm to themselves and to others
around them.
• Classification of drugs:
• Medicinal drugs
• Illegal drugs
1. ANTIBIOTICS KILL BACTERIA IN
THE BODY
• Antibiotics are substances that kill bacteria or prevent their
growth, but do not harm other living cells.
• Most of them are made by fungi.
• It is thought that the fungi make antibiotics to kill bacteria
living near them – bacteria and fungi are both decomposers,
so they might compete for food.
What are antibiotics?
Antibiotics are substances that kill bacteria or prevent their growth,
but do not harm other living cells..
Antibiotics are designed to kill bacteria (living organisms). They break down cell walls and membranes.
Interfere with their metabolism and damage DNA.
.
However, some types of bacteria
are no longer affected by certain
antibiotics – this is called
antibiotic resistance.
Can not destroy
viruses, since they do
not have a
metabolism
MEDICINAL IMPORTANCE OF ANTIBIOTICS
1. Inhibit synthesis of cell walls of bacteria so reduce their
reproduction.
2. Inhibits formation of protein in bacteria.
3. Disturb cell membrane function.
4. Affect enzyme action in bacteria.
BACTERIAL CELL
Viruses
• Characteristics like living organisms:
• Have a core of DNA or RNA
• Have protein
• Can reproduce
• Characteristics like non-living:
• Have no cytoplasm or cell organelles.
• Do not carry out any function of life
except reproduction inside living cells.
The first antibiotic to be discovered
was penicillin. It is made by the fungus
Penicillium. Penicillin kills bacteria by :
• preventing the production
of peptidoglycan that
form the cell wall:
• ---> the cell continue to
grow without dividing or
developing new cell wall
• --->the wall gets weaker
---> ruptures (lysis).
Antibiotics have either:
• Bacteriostatic action: by preventing bacterial growth
Ex: prevent the formation of cell wall.
• Bactericidal effect: they cause the bacteria to lysis or burst by
damaging its cell wall.
SOME BACTERIA DEVELOPED
RESISTANCE AGAINST ANTIBIOTICS
• Since the discovery of penicillin in 1928, many
more antibiotics have been developed and used to
treat bacterial infections.
• Some bacteria have mutated and become
resistant to antibiotics, but new drugs are
constantly being developed and tested
• The more we use antibiotics, the more selection
pressure we put on bacteria to evolve resistance.
What is MRSA?
MRSA is ‘Methicillin-resistant Staphylococcus aureus’ – a bacterium that is
resistant to several antibiotics.
About 30% of the population carry
MRSA without any symptoms.
In vulnerable hospital patients,
however, it can cause
pneumonia, blood poisoning and
even death.
The antibiotic vancomycin is
used to treat MRSA infection, but
resistance to this has evolved,
creating VRSA.
Antibiotic resistance: MRSA
The bacteria Staphylococcus
aureus has become resistant
to most antibiotics, including
methicillin. This methicillinresistant S. aureus (MRSA),
which is becoming common
in hospitals, can cause a
life-threatening infection.
Due to the emergence of antibiotic resistance, several
methods of prevention and control have been adopted:
 antibiotics should only be prescribed when needed

patients should finish the complete course of antibiotics

introduction of infection control in hospitals.
MRSA BACTERIA
• MRSA, (Methicillin-Resistant Staphylococcus aureus), is a
form of contagious bacterial infection that is resistant to
numerous antibiotics including methicillin, amoxicillin,
penicillin, and oxacillin. This resistance makes it challenging
to treat.
How population of antibiotic resistant bacteria as
MRSA can develop?
1- In normal bacterial population , on resistant cell may evolve by mutation.
2- Upon antibiotic treatment , all population is killed except for the resistant cell.
3- They by natural selection ( survival of fittest) , only the strain will reproduce.
4- Whole new population will be resistant to antibiotic treatment.
Development of resistant
bacteria such as MRSA can be
minimized by
ANTIBIOTICS DO NOT WORK AGAINST
VIRUSES.
• Many antibiotics kill bacteria by damaging their cell walls.
• Viruses do not have cell walls, so they are unharmed
by antibiotics.
Antibiotics
Advantages
Disadvantages
• Cures a lot of diseases
• Usually relieves symptoms in a
few days
• Reduces deaths from diseases
• Resistant bacteria can develop
• Diseases become more difficult
to treat
• Not taking the full course causes
more resistant bacteria to
survive
• Increases likelihood of them
working when you need
Antibiotics
sensitivity
test
Paper.6
ILLEGAL DRUGS
Types of drug
Type of drug
Effect on body
Example
Depressant
Slows down nerve and brain
activity
Alcohol, solvents, temazepam
Hallucinogen
Alters what we see and hear
LSD
Painkiller
Blocks nerve impulses
Aspirin, paracetamol
Performance enhancer Improves muscle development
Anabolic steroids
Stimulant
Nicotine, caffeine, ecstasy
Increases nerve and brain activity
Types of drug
• Stimulants and depressants affect the synapses between neurones in
the nervous system:
• stimulants cause more neurotransmitter molecules to diffuse across
the synapse
• depressants stop the next neurone sending nerve impulses. They
bind to the receptor molecules the next neurone that needs to
respond to the neurotransmitter molecules.
MISUSE OF DRUGS
alcohol
Effects of drugs
Drugs can have different effects on the body. These can be
grouped into five main categories:
 depressants – e.g. alcohol, solvents,
temazepan
 stimulants – e.g. caffeine,
nicotine, ecstasy
 painkillers– e.g. aspirin,
heroin, paracetemol
 hallucinogens – e.g. LSD
 performance enhancers
– e.g. anabolic steroids.
Why are drugs so dangerous?
Drugs can affect the way your brain works and cause damage
to your body. They make you more likely to have accidents
and make bad decisions.
People can become addicted to drugs. This
means that they develop a physical or mental
need for the drug.
An overdose is when someone takes too much of a drug.
This can cause death or serious illness.
You never know what other substances have been added to an
illegal drug, so these could cause unknown effects.
What is addiction?
A person is said to be addicted to, or dependent on, a drug when
they feel unable to stop taking it. There are two types of addiction:
 physiological addiction –
the person is compelled to take the
drug to avoid or reduce unpleasant
or dangerous withdrawal
symptoms.
 psychological addiction –
the person is compelled to take
the drug to experience the effect
it produces, rather than to treat
withdrawal symptoms.
How is addiction treated?
Addiction is treated by rehabilitation, which helps the user
to stop taking the drug.
Physiological addiction may initially be
treated using detoxification. In some
cases, substitute drugs may be prescribed
to reduce drug cravings or unpleasant
withdrawal symptoms.
For example, methadone is offered to
heroin addicts. Methadone is less
dangerous than heroin, but the aim is for
the addict to stop needing drugs altogether.
Psychological addiction is often treated using counselling.
REASONS FOR TAKING DRUGS SUCH AS HEROIN
AND ALCOHOL
• Social pressure
• Escape as some drugs help to forget problems
temporarily
• Creativity :some poets and writers did their best work
under the influence of drugs but there are thousands of
failures who are drug takers.
MISUSE OF DRUGS
2. EFFECTS OF HEROIN ABUSE(PERSONAL AND
SOCIAL PROBLEMS)
 Heroin is a powerful depressant.
 Depression of the central nervous system, decreasing the feel of pain.
 Respiratory depression, as the respiratory center can not send impulses to
the intercostal muscles to contract which slows down the rate of breathing.
This lead to death
 Death due too accidental overdose
 Loss of weight as the addict does not eat well.
 It is very addictive, leading to dependency (addiction).
 The person becomes unable to live without it.
• As withdrawal symptoms can be very unpleasant – involving cramp,
sleeplessness, violent vomiting, sweating and hallucinations.
It is a narcotic, producing a dream-like feeling of relaxation and
reducing severe pain
 May harm the body especially liver and brain cells
The body develops a tolerance to the drug, so an addict needs to
take increasing amount to achieve the same feeling. This leads to
the risk of overdosing on the drug.
When injected using unsterilized and shared needles, there is a risk
of infections such as hepatitis and HIV.
Addiction creates financial problems leading to family
breakdown, criminal activity and sexual promiscuity
HOW HEROIN AFFECTS NATURAL
NEUROTRANSMITTERS
• Endorphins are natural neurotransmitters that reduce sensation of
pain, affect mood and reduce sensation of hunger and pain and are
produced during exercise, injury and stress.
• When heroin enters the brain it is metabolized to morphine
which fit into endorphins receptors and make people feel good.
• Taking heroin reduces the production of natural endorphins and
also affect people brain production of other neurotransmitters
• Effect of Heroin on synapse:
1. In brain, heroin is metabolized to morphine.
2. Morphine binds to endorphin receptors in synapse
3. Endorphins is a group of neurotransmitters which affect mood and
reduce sensation of pain, this makes people feel good.
4. Heroin reduces the ability to produce natural endorphins and
other neurotransmitters.
3. HARMFUL EFFECTS DUE TO THE MISUSE OF ALCOHOL
A - Short term effects
1. Delays response (it increases the time of response as it has a
depressant effect) this may lead to accidents if driving or working on a
machine.
2. Disturbance in talking.
3. Double vision
4. Large doses may lead to loss of consciousness, coma and even death.
(Death is caused when a person is vomiting when unconscious due to the
effect of alcohol and then his airways become blocked by the vomit)
5. It can increase aggression in some people, so they are more likely to
be violent or commit crimes.
HARMFUL EFFECTS DUE TO THE MISUSE OF
ALCOHOL
B –Long term effects
1. Liver damage (cirrhosis) as the liver is the organ responsible for break
down of alcohol and other toxins. (Alcohol kills the liver cells which are
then replaced by fibers)
CONTINUED.. B –Long term effects
2. Weakens the heart muscles and may lead to heart attack.
3. Damages brain and nerves leading to loss of sensation. (this is because
alcohol in the tissue fluid surrounding the brain cells makes the tissue fluid
able to absorb water by osmosis from brain cells causing the cells to shrink)
4. May cause miscarriage of pregnant
5. Tolerance which means the body becomes in need for a greater amounts
of alcohol gain the same effect.
6. Dependence which means the person cannot feel well without the drug.
7. Excessive loss of water through urine.
CONTINUED..
C –Social Problems
Leads to violence and antisocial behavior.
Loss of friends and family relationships.
 Poor work performance and may result in loss of job.
Spending money on alcohol causes a shortage in spending on
family requirements and may lead to crimes to get money.
It is very addictive, leading to dependency (addiction).The
person becomes unable to live without it.
As withdrawal symptoms can be very unpleasant – involving
cramp, sleeplessness, violent vomiting, sweating..
ALCOHOLISM
 Long-term excessive drinking can lead to
addiction (alcoholism).
 This can lead to financial difficulties and family
problems.
 As the liver removes alcohol from the blood,
heavy drinking can lead to liver damage such
as cirrhosis.
 Excessive drinking can cause brain damage by
causing loss of memory and confusion.
 In addition it cause ulcers in the stomach and
obesity.
 Drinking during pregnancy can damage the
fetus, increase the risk of miscarriage or
premature birth, and reduce the average birth
weight
MCQS
3
4.
ANABOLIC
STEROIDS
• Steroid hormones include the reproductive hormones testosterone, oestrogen and
progesterone.
• Anabolic steroids build up large molecules from smaller ones such as building of
proteins from amino acids.
• Testosterone
 Causes more proteins to be made in muscle causing muscles to be larger and stronger.
 Also increases aggression which give someone an edge in competition.
• The used of steroid hormones in sports is banned because
 It gives someone unfair advantage
 In addition these decrease the ability of the immune system to destroy pathogens and
they can damage the liver.
Smoking and Health
1- Chronic Bronchitis
• inflammation of air passages like bronchioles and open to infection
from microorganism
2- Emphysema
• Excessive coughing causes the wall of alveoli in lungs to burst so the
surface area in contact with air is reduced.
5. TOBACCO SMOKING
• Tobacco smoke contains irritants and carcinogens.
• Its 4 main toxic chemicals: carbon monoxide, nicotine, smoke particles and tar.
Smoking cigarette
•
The effect of cigarette smoke
Carbon monoxide
• It combines with haemoglobin
forming carboxy-haemoglobin
[ permanently] which reduces
the oxygen carried by the
blood.
• Babies born to mothers who
smoke tend to be smaller as
result of lack of oxygen.
SOME OF THE SUBSTANCES IN TOBACCO SMOKE.
• Carbon monoxide:
• Effect on respiratory system
A poisonous gas which combines with haemoglobin
forming carboxy-haemoglobin in RBC ---> prevents
them transporting O2.
Babies born to mothers who smoke tend to be
smaller as a result of lack of oxygen
SOME OF THE SUBSTANCES IN TOBACCO SMOKE.
• Nicotine:
• Effect on respiratory system
 It is a stimulant which means a person feel more alert and active
 Addictive resulting in the continuation of smoking, exposing lung to harmful
chemicals.
• Effect on other systems
It increases the tendency for fatty deposits to form inside blood vessels
• causing blood vessels to lose their elasticity and to become narrow.
It affects the nervous and circulatory system by increasing the release of
adrenaline hormone which increases heart rate and rises blood pressure by
causing the construction of many blood vessels.
Can pass to the blood of fetus from its mother resulting in reduced birth weight.
The effect of cigarette smoke
Nicotine
• It is a stimulant [ makes you more alert and active ].
• It is addictive , means that once your body has got used to it, it is very hard to do without it.
• Affects the nervous and circulatory systems. In general it acts as stimulant by increasing the release
of adrenaline hormone that:
increases the rate of heart beat and
increase the blood pressure by causing constriction of many blood vessels.
• It increases the tendency for fatty deposits to form inside the blood vessels causing blood vessels to
lose their elasticity and become narrow [ that is called atherosclerosis]
SOME OF THE SUBSTANCES IN TOBACCO SMOKE.
• Tar:
• Effect on respiratory system
- A carcinogen: increase risk of lung cancer ( cell division out of
control)
- Irritates the linings of the trachea :
-which increase mucus production
 - paralysing + damaging cilia
---> causing bronchitis and emphysema
The effect of cigarette smoke
Tar
• It is a carcinogenic substance [ lead to lung cancer].
• Irritates the lining of trachea causing the production of more mucus and
the cilia stop beating therefore:
Coughing takes place to expel mucus.
Coughing damages the lining of bronchioles and allow it to be attacked by
viruses and bacteria causing chronic bronchitis.
Excessive coughing can breakdown the thin walls of alveoli decreasing the
surface area of gaseous exchange. And this is called emphysema.
The effect of cigarette smoke
Smoke particles
• When inspired , inflammation takes place causing the inner lining of the
gaseous exchange surface to swell so the lumen of the respiratory pathway
decreases leading to difficulty in breathing, abnormal cough and may lead to
emphysema
• Caused asthma
• Tigger white blood cells and the lymphocytes engulf the smoke particles by
phagocytosis.
• Smoke particles
1) Emphysema
Emphysema is a disease in which the thin walls of the alveoli break down. Smoke droplets
condense onto the alveolar wall, making them rigid and inflexible. Smokers are coughing a great
deal to remove the mucus from their lungs and this coughing can cause the sticky, rigid tar coated
alveolar wall to degenerate.
COPD
Chronic Obstructive Pulmonary Disease.
• 2) Chronic obstructive pulmonary disease (COPD)
• Smoke particles are little particles of carbon and other materials that get
trapped inside the lungs.
• When white blood cells try to remove the smoke particles, the
substances secreted by white blood cells can damage the lungs
themselves
SMOKING AND HEART DISEASE
• Patients who smoke have a higher blood
pressure than normal due to the stimulant
effects of nicotine.
• A high blood pressure makes the early damage to the
arterial lining more likely as well as making the blood
more likely to clot.
• Blood clots form in the final stages of the disease
around the plaque and can complete block the
blood vessel.
• CHD is a major cause of death across the world
and
it is well known that stopping smoking can do a great
deal to lower a patient’s risk of this potentially deadly
disease.
SMOKING AND LUNG CANCER
• Carcinogens in cigarette smoke can make it much
more likely that cells in the lungs and airways develop
mutations that lead to cancer.
• Cancer is a disease in which cells start to divide out
of control to form a tumor
• Lung cancers can be hard to treat and are a
common cause of early death in cigarette smokers.
QUESTION
• The table shows the percentage of haemoglobin which is inactivated by CO present in
the blood of taxi drivers in a city.
Common misconceptions
Remember that only
nicotine and carbon
monoxide enter the blood.
Tar and smoke particles
do not – they stay in the
lungs.
Evidences for the link between smoking and lung cancer
1- Smokers are more likely to develop lung cancer than non smokers.
2- One third of all the cancer deaths are due to smoking.
3- 25 % of the smokers die of lung cancer.
4- The risk of developing lung cancer starts to decrease as soon as smoking is
stopped.
5- Risk of developing lung cancer increases:
in those start smoking in early age, also
increasing number of cigarettes and
Increasing tar content of cigarettes.
Other effects of smoking
Physical dependence
• Because tobacco stimulates the nervous system , stop smoking leads to
symptoms such as sleeplessness , muscle pain , headache and nausea.
Psychological dependence
• Many people can’t stop smoking because they think that smoking increases
self confidence or increases nervous concentration.
• Many people can’t stop smoking because it is linked with some activities such
as drinking coffee , watching T.V
Tolerance
• Means that the smoker must smoke more and more to get the same effect.
Passive
smoking
Inhaling smoke of cigarettes
from the surrounding air by
Non-smokers