GCSE Biology revision

Resistant bacteria

The development of understanding of genetics and evolution

AQA 4.1.1.1

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Identify and describe Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues in the context of resistant bacteria.

MOST 🎯🎯

Explain the relationships between Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues and how they contribute to resistant bacteria.

SOME 🎯🎯🎯

Apply and analyse knowledge of Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues to interpret unfamiliar information about resistant bacteria.

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

Natural Sources of Drugs

Microorganisms and plants have evolved over millions of years to produce substances that can kill pathogens, providing a natural starting point for drug development
Aspirin, a common painkiller used to lower fevers, was originally derived from a chemical found in the bark of willow trees
Digitalis, used to treat heart problems such as heart failure, was originally developed from a chemical found in foxglove plants
Penicillin, the first and most widely used antibiotic, was discovered by Alexander
Fleming when he noticed a fungus (Penicillium) had killed surrounding bacterial colonies in a petri dish

1. Natural Sources of DrugsAQA

Notes

Microorganisms and plants have evolved over millions of years to produce substances that can kill pathogens, providing a natural starting point for drug development
Aspirin, a common painkiller used to lower fevers, was originally derived from a chemical found in the bark of willow trees
Digitalis, used to treat heart problems such as heart failure, was originally developed from a chemical found in foxglove plants
Penicillin, the first and most widely used antibiotic, was discovered by Alexander
Fleming when he noticed a fungus (Penicillium) had killed surrounding bacterial colonies in a petri dish

Key Criteria When Testing Drugs

Efficacy refers to how well a drug produces its desired effect, such as how effectively an antibiotic kills bacteria
Toxicity describes how harmful a drug is to the body, including whether it damages cells or causes side effects
Dosage refers to the amount or concentration of a drug that should be given to a patient
Generally, a higher dose increases efficacy but also increases the risk of side effects, so finding the right balance is essential

2. Key Criteria When Testing DrugsAQA

Notes

Efficacy refers to how well a drug produces its desired effect, such as how effectively an antibiotic kills bacteria
Toxicity describes how harmful a drug is to the body, including whether it damages cells or causes side effects
Dosage refers to the amount or concentration of a drug that should be given to a patient
Generally, a higher dose increases efficacy but also increases the risk of side effects, so finding the right balance is essential

Stage 1: Testing on Cells and Tissues

In the first stage of drug testing, substances are tested on human cells and tissues grown in a laboratory
This stage allows scientists to test many different substances quickly and cheaply
A key limitation is that testing on isolated cells and tissues does not reveal how the substance would affect a whole organism or a specific organ

3. Stage 1: Testing on Cells and TissuesAQA

Notes

In the first stage of drug testing, substances are tested on human cells and tissues grown in a laboratory
This stage allows scientists to test many different substances quickly and cheaply
A key limitation is that testing on isolated cells and tissues does not reveal how the substance would affect a whole organism or a specific organ

Stage 2: Pre-Clinical Testing on Animals

If a substance shows promise in cell and tissue tests, it progresses to testing on live animals, such as mice and rabbits
In the UK, all drugs must be tested on at least two different types of live mammals before moving to human trials
Because humans are also mammals, animal testing gives a good indication of a drug's efficacy and toxicity
Stages 1 and 2 are collectively referred to as pre-clinical testing, as they do not involve human participants

4. Stage 2: Pre-Clinical Testing on AnimalsAQA

Notes

If a substance shows promise in cell and tissue tests, it progresses to testing on live animals, such as mice and rabbits
In the UK, all drugs must be tested on at least two different types of live mammals before moving to human trials
Because humans are also mammals, animal testing gives a good indication of a drug's efficacy and toxicity
Stages 1 and 2 are collectively referred to as pre-clinical testing, as they do not involve human participants

Stage 3: Clinical Testing — Healthy Volunteers

Clinical testing is the final stage of drug development and involves giving the drug to human participants for the first time
The drug is initially given to healthy volunteers at a very low dose to check for any immediate harmful effects
The dose is gradually increased while doctors closely monitor the volunteers for any side effects
The aim at this step is to identify the maximum dosage that can be administered before side effects begin to appear

5. Stage 3: Clinical Testing — Healthy VolunteersAQA

Notes

Clinical testing is the final stage of drug development and involves giving the drug to human participants for the first time
The drug is initially given to healthy volunteers at a very low dose to check for any immediate harmful effects
The dose is gradually increased while doctors closely monitor the volunteers for any side effects
The aim at this step is to identify the maximum dosage that can be administered before side effects begin to appear

Stage 3: Clinical Testing — Patient Trials

Once safety in healthy volunteers is established, the drug is given to patients who have the specific illness the drug is designed to treat
The dose is again increased gradually, this time to find the optimum dosage where efficacy is maximised and toxicity is minimised

Placebos and Blind Trials

A placebo is a substance that looks identical to the real drug but contains no active medication, often made from sugar
In a blind trial, half of the volunteers receive the real drug and the other half receive the placebo, but participants are not told which they have been given
In a double-blind trial, neither the volunteers nor the doctors know who has received the real drug until all results have been analysed
Using blind and double-blind methods helps to eliminate unconscious bias, such as volunteers being more likely to report side effects if they know they are taking the real drug

7. Placebos and Blind TrialsAQA

Notes

A placebo is a substance that looks identical to the real drug but contains no active medication, often made from sugar
In a blind trial, half of the volunteers receive the real drug and the other half receive the placebo, but participants are not told which they have been given
In a double-blind trial, neither the volunteers nor the doctors know who has received the real drug until all results have been analysed
Using blind and double-blind methods helps to eliminate unconscious bias, such as volunteers being more likely to report side effects if they know they are taking the real drug

Peer Review

Once drug testing is complete, the results are written up and submitted for peer review, where other scientists analyse the study to check that the tests were fair and valid
Peer review is a fundamental part of the scientific process and helps to prevent false claims or inaccurate results from being published

Summary of the Drug Testing Process

The drug testing process moves through three main stages: laboratory testing on cells and tissues, pre-clinical testing on live animals, and clinical testing on humans
This staged approach ensures that only safe and effective drugs reach patients, protecting public health
The entire process, from discovery to approval, is designed to rigorously evaluate a drug's efficacy, toxicity, and optimum dosage

9. Summary of the Drug Testing ProcessAQA

Notes

The drug testing process moves through three main stages: laboratory testing on cells and tissues, pre-clinical testing on live animals, and clinical testing on humans
This staged approach ensures that only safe and effective drugs reach patients, protecting public health
The entire process, from discovery to approval, is designed to rigorously evaluate a drug's efficacy, toxicity, and optimum dosage