Drugs and Their Effects | Cambridge IGCSE Biology

This IGCSE Biology presentation explores drugs and their effects on the human body, covering medicinal drugs, recreational drugs, and drug abuse. Learn about the impact of stimulants, depressants, painkillers, hallucinogens, and performance-enhancing drugs, as well as the dangers of alcohol, nicotine, and illegal substances. Ideal for Cambridge IGCSE students looking to understand this important topic for exams!

2. Drugs
Objectives
• Define a drug as any substance taken into the body that
modifies or affects chemical reactions in the body
• Describe the use of antibiotics for the treatment of bacterial
infection
• State that some bacteria are resistant to antibiotics which
reduces
the effectiveness of antibiotics
• State that antibiotics kill bacteria but do not affect viruses
• Explain how development of resistant bacteria such as MRSA can
be
minimised, limited to using antibiotics only when essential and
ensuring
treatment is completed
• Explain why antibiotics kill bacteria, but do not affect viruses
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3. Drugs
Any substance taken into the body that
modifies or affects chemical reactions in the
body .
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4. Medicinal drugs : antibiotic
A type of chemical made by microorganisms (or
made artificially) used to kill bacterial and fungal
pathogens or stop their growth
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5. Pathogens & Antibiotics
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Antibiotics
•These are drugs that kill bacteria inside the body.
•They don’t kill viruses.
The antibiotics that can :
• Only kill specific bacteria are called narrow spectrum antibiotics.
• Broad spectrum antibiotics can kill a larger variety of pathogen

6. Microorganisms and disease
•Some bacteria and viruses can cause disease.
•A microorganism that causes disease is called a pathogen.
•If bacteria can get into the body, it reproduces rapidly.
•They produce toxins that make you feel ill.
•They are carried in the blood.
•A virus can get into a cell and reproduce there.
•When too much is produced they can burst out of the cell and
destroy it.
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•Antibiotics work either by damaging the cell
wall or inhibiting the metabolism in a cell of the
pathogen.
•Since viruses do not have cells and they occupy
host cells antibiotics can not work on them .

8. Drugs against disease
Sources of antibiotics
•Penicillin is made from a fungus.
•The drug companies are always on the look out for new antibiotics.
•Nowadays, most antibiotics are made chemically.
•This is better then extracting them from fungi or other organisms
because you know what you're getting.
•If you take it from fungus, you don’t know the strength of it.
•Making it chemically means you know its pure
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9. Explain why antibiotics are not used
for the treatment of viral diseases.
❑antibiotics are effective against cells;
❑stop cell wall growth;
❑stop protein synthesis;
❑stop metabolism;
❑viruses have no cell wall;
❑do not have any metabolism of their own;
❑rely on host cell’s metabolism for their
reproduction
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10. Viruses
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11. How a Virus Invades a Cell
a) attachment of virus to host cell
b) injection of viral DNA
c) Integration of the viral DNA into host
genome, and
d) Multiplication of the host cell with the
viral DNA.
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16. Antibiotics
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17. Antibiotics resistance bacteria
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18. Antibiotic sensitivity test
•Culture of sample of patient’s
urine , stools , wound pus or any
body fluid to identify the name of
bacteria and the highly sensitive
antibiotics may be used to kill
bacteria.
This technique is used in medical
labs to help doctors reduce the
antibiotics resistant bacteria.
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