WS / HW / / RS /136 : 2022 - 2023: TERM: I/II
NAME________________________ CLASS: 9 DIV: A B C D E ROLL NO.: ____ DATE: ____________
SUBJECT: Biology TOPIC: Drugs(notes) TEACHER’S NAME: Ms.Bhavana Asrani
Note: This sheet can be assessed. MARKS / GRADE: ___
____________________________________________________________________________
Drugs
A drug is a chemical substance used in treatment, cure, prevention, or diagnosis of diseases, or
otherwise used to enhance physical or mental wellbeing.
Key Definition: Any substance taken into the body that modifies or affects chemical reactions in
the body is called as a drug
Antibiotics
Antibiotics like penicillin are chemicals that kill bacteria by destroying their cell walls. They do not
harm our body cells when doing so as animal cells don’t have cell walls.
They are very useful for killing bacteria. However, they are useless against viruses as viruses
don’t have cell walls.
unless they are used intensively (as intensive use exerts a selection pressure upon them, causing
the bacteria to get resistant to them)
Antibiotic resistance
Since Penicillin was discovered in 1928, the use of antibiotics for the treatment of diseases has
increased exponentially. Antibiotics are being overused in many ways in our world today. Over
time, bacteria can become resistant to certain antibiotics.
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Problems with antibiotics
Commonly prescribed antibiotics are becoming less effective due to a number of reasons:
Overuse of antibiotics- People feel unwell and when going to the doctors, they expect antibiotics
to be prescribed. If patients have viral infections, such as the common cold and not a bacterial
one, the antibiotics are ineffective and unnecessary.
Failing to complete the fully prescribed course by a doctor- Patients should always fully
complete the prescribed course of antibiotics, every time they are taken. This ensures all bacteria
are killed, and so none survive.This is potentially very harmful, as random mutations can occur
which can lead to antibiotic resistance. The resistant bacteria reproduce quickly, and the resistance
spreads.
MRSA
MRSA is methicillin-resistant staphylococcus aureus (not to be learnt). It is very dangerous because
it is resistant to most antibiotics.
To slow down or stop the development of other strains of resistant bacteria, we should:
avoid the unnecessary use of antibiotics
always complete the full course
Development of resistance
The main steps in the development of resistance are:
1. random mutations occur in the genes of individual bacterial cells
2. some mutations protect the bacterial cell from the effects of the antibiotic
3. bacteria without the mutation die or cannot reproduce when the antibiotic is present
4. resistant bacteria can reproduce with less competition from normal bacterial strains
Ways to reduce antibiotic resistance
Only take antibiotics when necessary.
Treat specific bacteria with specific antibiotics.
High hospital hygiene levels, including regular hand washing by staff and visitors.
Patients who are infected with antibiotic resistant strains of bacteria should be isolated from
other patients.
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