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Summary Topic 15: Drugs
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Topic 15: Drugs: IGCSE Biology course notes which will help you study for your papers. By studying these notes I achieved a 9 - A* on my Igcse
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IGCSE Biology Topic 1 (Characteristics & Classification of Living Organisms)
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Class notes biology: Characteristics of living organisms
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Class and mark scheme notes Biology Cambridge IGCSE with Biology Coursebook with CD-ROM
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TOPIC 15: DRUGS1.1 DRUGS
→Drugs: any substance taken into your body that modifies or affects chemical reactions in the body.
1.2 MEDICINAL DRUGS
-Some drugs are medicinal drugs that are used to treat the symptoms or causes of a disease – for example, antibiotics.
→Antibiotics: chemical substances made by certain fungi or bacteria that affect the working of bacterial cells, either by
disrupting their structure or function or by preventing them from reproducing.
-First antibiotic was called Penicillin (made with fungus penicillium)
-Antibiotics are effective against bacteria but not against viruses.
-Antibiotics target processes and structures (i.e. cell walls) that are specific to bacterial (prokaryotic) cells; as such they do not
generally harm animal cells.
Effectiveness of Antibiotics
-Some bacteria that lead to disease have become resistant to
antibiotics and this reduces the effectiveness of prescribed antibiotics
when someone has a bacterial infection, as it might be caused by a
type of bacteria that is resistant to that particular antibiotic.
Why don't Antibiotics Affect Viruses?
-Viruses cannot be treated with antibiotics
-This is because antibiotics work by disrupting cell processes such as
respiration, or breaking down the structure (cell wall) of the cell in
some way.
-However, viruses don’t carry out any cell processes and don’t have
cell walls, cell membranes or any cell organelles as viruses infect and use the machinery of animal cells to reproduce (depend on
the host cell), which are not affected by antibiotics.
-Therefore, the action of antibiotics doesn’t affect them.
Antibiotic Resistance
-Since the first antibiotic was discovered, antibiotics have been
widely overused.
-Commonly prescribed antibiotics are becoming less effective due
to a number of reasons:
→overuse and being prescribed when not really necessary
→patients failing to complete the fully prescribed course
by a doctor
→excessive use of antibiotics in farming to prevent
disease when livestock are kept in close, even when animals are
not actually sick.
-This has led to the effectiveness of antibiotics being reduced, and
the incidence of antibiotic resistance increasing
-These bacteria are commonly known as superbugs and the most
common is MRSA
-Ways individuals can help prevent the incidence of antibiotic
resistance increasing include:
→only taking antibiotics when absolutely essential
→when prescribed a course of antibiotics, ensure that the entire course is completed even if you feel better after a few
days.
15.2 MISUSED DRUGS
-Most alcoholic drinks contain an alcohol called ethanol.
-It is a depressant drug – it slows down signals in the nerves and brain
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