Drugs In Medicine

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Notes

What is a drug?

A **drug** is any substance taken into the body that modifies or affects chemical reactions in the body.
**Medicinal drugs** are used to treat the symptoms or causes of a disease (e.g., antibiotics).
The **liver** is the primary site of drug metabolism.

Antibiotics

**Antibiotics** are chemical substances made by certain fungi or bacteria.
They affect bacterial cells by disrupting their structure/function or preventing reproduction.
Antibiotics are effective against **bacteria** but **not against viruses**.
They target processes/structures specific to prokaryotic cells, so they generally do not harm animal cells.

Antibiotic resistance

Overuse and unnecessary prescribing of antibiotics reduce their effectiveness.
Patients failing to complete the full prescribed course contributes to resistance.
Large-scale use in farming (even when animals are not sick) increases resistance.
Resistant bacteria are called **superbugs** (e.g., MRSA).

Preventing antibiotic resistance

Only take antibiotics when absolutely essential.
Always complete the entire prescribed course, even if you feel better.
Doctors should not prescribe antibiotics for viral infections.

Antibiotics target bacteria, disrupting their structure or reproduction.

Antibiotic resistance: some bacteria survive and multiply, becoming superbugs.

Practice questions

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1.Which of the following gives the most accurate definition of a drug?
Easy
- AAn addictive or harmful substance.
- BA substance taken into the body that modifies or affects chemical reactions.
- CA plant extract that kills bacteria.
- DA substance that produces side effects as well as therapeutic effects.
2.Which organ is the primary site of drug metabolism?
Easy
- AKidney
- BLiver
- CHeart
- DLungs
3.Which group of drugs is used to treat the symptoms or causes of a disease?
Easy
- AAntibiotics
- BMedicinal drugs
- CPainkillers
- DVaccines
4.Which class of drugs is used to treat bacterial infections?
Easy
- AAntibiotics
- BAntivirals
- CPainkillers
- DVaccines
5.Antibiotics are effective against bacteria but not against viruses because
Medium
- Aviruses have cell walls that are different from bacterial cell walls
- Bviruses do not have the cellular structures that antibiotics target
- Cviruses are too small for antibiotics to affect
- Dviruses produce enzymes that break down antibiotics
6.A patient feels better after taking only part of a prescribed course of antibiotics. Why is it important to complete the full course?
Medium
- ATo ensure all bacteria are killed and reduce the chance of resistance developing
- BTo prevent side effects from stopping early
- CTo make the antibiotics work faster
- DTo avoid the infection becoming viral
7.Which of the following is NOT a reason why antibiotics are becoming less effective?
Medium
- AOveruse of antibiotics in farming
- BPatients failing to complete the full course
- CAntibiotics 'wearing out' through overuse
- DBacteria evolving defence mechanisms
8.What is the name of the small circular loop of DNA that can be passed between bacterial cells and can carry antibiotic resistance genes?
Medium
- AChromosome
- BPlasmid
- CRibosome
- DNucleoid

More questions

9.Which of the following statements about antibiotics is not correct?
Medium
- ASome antibiotics are produced by fungi.
- BSome bacteria are resistant to antibiotics.
- CAntibiotics are used to treat diseases caused by viruses.
- DWhen taking antibiotics for an infection, the course of treatment should be completed.
10.In a laboratory experiment, paper discs soaked in different antibiotics are placed on a bacterial lawn. A clear zone around a disc indicates that the bacteria are
Hard
- Aresistant to the antibiotic
- Bsusceptible to the antibiotic
- Ckilled by the antibiotic only at the disc edge
- Dunaffected by the antibiotic
11.Which of the following is a reason why antibiotics generally do not harm human cells?
Hard
- AHuman cells have cell walls that protect them
- BHuman cells do not have the specific targets that antibiotics act on in bacteria
- CHuman cells are too large for antibiotics to enter
- DHuman cells produce enzymes that break down antibiotics
12.A scientist discovers a new molecule that stops bacteria from reproducing but does not kill them. Why might this still be useful as an antibiotic?
Hard
- AIt will kill the bacteria eventually
- BIt prevents the infection from spreading, allowing the immune system to clear the bacteria
- CIt will cause the bacteria to become resistant more quickly
- DIt can be used to treat viral infections as well
13.In a study, the levels of three antibiotics (A, B, C) were measured in stream water upstream and downstream of a dumpsite. The upstream levels were: A=10, B=8, C=3 (arbitrary units). Downstream levels were: A=12, B=34, C=2. What is the percentage increase of antibiotic B from upstream to downstream?
Medium
- A325%
- B425%
- C26%
- D34%
14.A scientist tests two bacterial strains (X and Y) with antibiotics using the disk diffusion method. On the agar plate with strain X, there is a clear zone around the penicillin disk but no zone around the methicillin disk. On the plate with strain Y, there is no clear zone around either disk. What can be concluded?
Medium
- AStrain X is resistant to penicillin, strain Y is resistant to both.
- BStrain X is sensitive to penicillin but resistant to methicillin; strain Y is resistant to both.
- CStrain X is sensitive to both antibiotics; strain Y is resistant to both.
- DStrain X is resistant to methicillin but sensitive to penicillin; strain Y is sensitive to both.
15.The diagram shows the results of an antibiotic sensitivity test using paper discs on a bacterial lawn. Disc 1 (control) shows no clear zone. Disc 2 (antibiotic P) shows a clear zone of 15 mm. Disc 3 (antibiotic Q) shows a clear zone of 8 mm. Disc 4 (antibiotic R) shows no clear zone. Which antibiotic is most effective against this bacterium?
Hard
- AAntibiotic P
- BAntibiotic Q
- CAntibiotic R
- DCannot be determined
16.Which of the following is a method by which bacteria can become resistant to antibiotics?
Easy
- AMutation of bacterial DNA
- BThe antibiotic wearing out
- CThe patient taking the full course of antibiotics
- DThe antibiotic being produced by fungi
17.A new antibiotic is discovered that prevents bacterial ribosomes from functioning. Why is this antibiotic unlikely to harm human cells?
Medium
- AHuman cells do not have ribosomes.
- BHuman ribosomes are structurally different from bacterial ribosomes.
- CThe antibiotic is broken down in the human stomach.
- DHuman cells are protected by a cell wall.
18.In a hospital, 100 patients with a bacterial infection are treated with antibiotic X. After treatment, 95 recover, but 5 do not and their bacteria are found to be resistant to X. Which statement best explains this?
Hard
- AThe antibiotic caused the bacteria to mutate.
- BSome bacteria were already resistant before treatment.
- CThe patients did not take the full course.
- DThe antibiotic was not strong enough.
19.Which of the following is a way to reduce the development of antibiotic resistance?
Easy
- AUsing antibiotics to treat viral infections
- BStopping antibiotics as soon as symptoms disappear
- CCompleting the full course of antibiotics as prescribed
- DUsing antibiotics in animal feed to prevent disease
20.The table shows the minimum inhibitory concentration (MIC) of an antibiotic for two bacterial strains. Strain A: MIC = 2 μg/mL. Strain B: MIC = 32 μg/mL. Which strain is more resistant to the antibiotic?
Medium
- AStrain A
- BStrain B
- CBoth are equally resistant
- DCannot be determined
21.In an experiment, bacteria are exposed to a sub-lethal concentration of an antibiotic for many generations. After 100 generations, the MIC increases 10-fold. What is the most likely explanation?
Hard
- AThe antibiotic has degraded over time.
- BThe bacteria have evolved resistance through natural selection.
- CThe bacteria have learned to avoid the antibiotic.
- DThe antibiotic concentration was too low.
22.What is the primary site of drug metabolism in the human body?
Easy
- AKidney
- BLiver
- CLungs
- DHeart
23.A student places paper discs soaked in different concentrations of an antibiotic on a bacterial lawn. The diameters of the clear zones are: 0 μg/mL: 0 mm; 1 μg/mL: 5 mm; 10 μg/mL: 15 mm; 100 μg/mL: 20 mm. What conclusion can be drawn?
Medium
- AThe antibiotic is ineffective at all concentrations.
- BIncreasing concentration increases the zone of inhibition, but with diminishing returns.
- CThe bacteria are completely resistant to the antibiotic.
- DThe antibiotic works best at 1 μg/mL.
24.A new drug is discovered that inhibits an enzyme unique to bacteria. In clinical trials, it kills 99.9% of bacteria in a culture. However, after several days, the bacteria grow back. Which is the most likely explanation?
Hard
- AThe drug caused mutations that made the bacteria resistant.
- BA few resistant bacteria survived and multiplied.
- CThe drug lost its effectiveness over time.
- DThe bacteria formed a biofilm that protected them.
25.In a disk diffusion test, a paper disc soaked in antibiotic is placed on a bacterial lawn. After incubation, a clear zone of 15 mm is observed around the disc. What does this clear zone indicate?
Medium
- AThe bacteria are resistant to the antibiotic.
- BThe antibiotic has diffused into the agar and inhibited bacterial growth.
- CThe bacteria have produced an enzyme that breaks down the antibiotic.
- DThe disc was not properly soaked in the antibiotic.
26.A student sets up an experiment to test the effectiveness of three antibiotics (X, Y, Z) against a bacterial strain. Paper discs soaked in each antibiotic are placed on an agar plate spread with bacteria. After incubation, the diameters of the clear zones are: X = 12 mm, Y = 8 mm, Z = 18 mm. Which antibiotic is most effective against this strain?
Medium
- AAntibiotic X because it produced a zone of 12 mm.
- BAntibiotic Y because it produced the smallest zone.
- CAntibiotic Z because it produced the largest zone.
- DCannot be determined because the disc sizes may differ.
27.In an experiment, a bacterial culture is treated with a sub-lethal concentration of an antibiotic. After many generations, the minimum inhibitory concentration (MIC) increases from 2 μg/mL to 32 μg/mL. What is the most likely explanation for this change?
Hard
- AThe antibiotic has degraded over time, becoming less potent.
- BThe bacteria have mutated and acquired resistance to the antibiotic.
- CThe culture was contaminated with a different bacterial species.
- DThe antibiotic concentration was measured incorrectly.
28.The table shows the minimum inhibitory concentration (MIC) of an antibiotic for two bacterial strains. Strain A: MIC = 2 μg/mL. Strain B: MIC = 32 μg/mL. Which statement is correct?
Medium
- AStrain A is more resistant than Strain B.
- BStrain B is more resistant than Strain A.
- CBoth strains are equally sensitive to the antibiotic.
- DStrain A requires a higher dose to be killed.
29.A new antibiotic is discovered that inhibits bacterial ribosomes. Why is this antibiotic unlikely to harm human cells?
Hard
- AHuman cells do not have ribosomes.
- BHuman ribosomes are structurally different from bacterial ribosomes.
- CHuman cells are protected by a cell wall.
- DThe antibiotic is broken down by human enzymes before reaching ribosomes.
30.In a hospital, 100 patients with a bacterial infection are treated with antibiotic X. After treatment, 95 recover, but 5 do not and their bacteria are found to be resistant to X. Which of the following is the most likely explanation for the resistance in these 5 patients?
Medium
- AThe bacteria in these patients mutated after exposure to antibiotic X.
- BThese patients were infected with a resistant strain before treatment.
- CThe antibiotic X was not stored properly and lost potency.
- DThe patients did not complete the full course of antibiotics.
31.A student places paper discs soaked in different concentrations of an antibiotic on a bacterial lawn. The diameters of the clear zones are: 0 μg/mL: 0 mm; 1 μg/mL: 5 mm; 10 μg/mL: 12 mm; 100 μg/mL: 18 mm. What conclusion can be drawn?
Hard
- AThe antibiotic is more effective at higher concentrations.
- BThe bacteria are completely resistant to the antibiotic.
- CThe antibiotic is not diffusing into the agar.
- DThe zone size is independent of concentration.
32.A new drug is discovered that inhibits an enzyme unique to bacteria. In clinical trials, it kills 99.9% of bacteria in a culture. However, after several days, the bacterial population recovers. What is the most likely reason?
Medium
- AThe drug lost its effectiveness over time.
- BA small number of resistant bacteria survived and multiplied.
- CThe drug was not administered at a high enough dose.
- DThe bacteria formed a biofilm that protected them.
33.In a study, the levels of three antibiotics (A, B, C) were measured in stream water upstream and downstream of a dumpsite. The upstream levels were: A=10, B=8, C=3 arbitrary units. Downstream levels were: A=12, B=34, C=2. Which antibiotic shows the greatest percentage increase?
Hard
- AAntibiotic A with a 20% increase.
- BAntibiotic B with a 325% increase.
- CAntibiotic C with a 33% decrease.
- DAntibiotic B with a 425% increase.
34.Which of the following is the most accurate definition of a drug?
Easy
- AA substance taken into the body that modifies or affects chemical reactions in the body.
- BAn addictive or harmful substance.
- CA plant extract that kills bacteria.
- DA substance that produces side effects as well as therapeutic effects.
35.A student investigates the effect of an antibiotic on bacterial growth using the disk diffusion method. The student places paper discs soaked in different concentrations of the antibiotic on an agar plate spread with bacteria. After incubation, the diameters of the clear zones are measured. Which of the following graphs best represents the expected relationship between antibiotic concentration and zone diameter?
Medium
- AA: Zone diameter increases linearly with concentration.
- BB: Zone diameter increases with concentration but reaches a plateau at high concentrations.
- CC: Zone diameter decreases with concentration.
- DD: Zone diameter is constant regardless of concentration.
36.In an experiment, a bacterial culture is exposed to a sub-lethal concentration of an antibiotic for many generations. After 100 generations, the minimum inhibitory concentration (MIC) of the antibiotic for the culture increases from 2 μg/mL to 32 μg/mL. Which of the following best explains this observation?
Hard
- AA: The antibiotic induced mutations in the bacteria that conferred resistance.
- BB: The bacteria gradually adapted to the antibiotic by changing their metabolism.
- CC: Natural selection favored resistant mutants that were already present in the population.
- DD: The antibiotic concentration was too low to kill any bacteria, so no selection occurred.
37.A study measured the levels of three antibiotics (A, B, and C) in stream water upstream and downstream of a dumpsite. The results are shown in the table. | Antibiotic | Upstream level (arbitrary units) | Downstream level (arbitrary units) | |------------|---------------------------------|-----------------------------------| | A | 10 | 12 | | B | 8 | 34 | | C | 3 | 2 | Calculate the percentage increase in antibiotic B from upstream to downstream.
Medium
- AA: 26%
- BB: 325%
- CC: 425%
- DD: 26%
38.A new antibiotic is discovered that inhibits an enzyme unique to bacteria. In clinical trials, it kills 99.9% of bacteria in a culture. However, after several days, the culture regrows. Which of the following is the most likely explanation?
Medium
- AA: The antibiotic lost its effectiveness over time due to chemical breakdown.
- BB: The surviving bacteria were resistant and multiplied.
- CC: The antibiotic killed only Gram-positive bacteria, and Gram-negative bacteria survived.
- DD: The bacteria mutated to produce a different enzyme that the antibiotic could not inhibit.
39.In a disk diffusion test, a paper disc soaked in antibiotic is placed on a bacterial lawn. After incubation, a clear zone of 15 mm is observed around the disc. The same antibiotic is tested on a different bacterial strain, and the clear zone is 5 mm. Which of the following conclusions is most valid?
Hard
- AA: The second strain is more resistant to the antibiotic than the first strain.
- BB: The antibiotic diffused less in the second plate.
- CC: The second strain grows more slowly.
- DD: The first strain is resistant to the antibiotic.
40.A student places paper discs soaked in different concentrations of an antibiotic on a bacterial lawn. The diameters of the clear zones are: 0 μg/mL: 0 mm; 1 μg/mL: 5 mm; 10 μg/mL: 12 mm; 100 μg/mL: 15 mm. Which of the following is the most likely explanation for the small increase in zone diameter between 10 μg/mL and 100 μg/mL?
Medium
- AA: The bacteria have become resistant to high concentrations.
- BB: The antibiotic has reached its limit of diffusion in the agar.
- CC: The antibiotic is toxic to the bacteria only at low concentrations.
- DD: The experiment was not carried out correctly.

Slides

What is a drug?

A drug is any substance taken into the body that modifies or affects chemical reactions in the body.
Some drugs are medicinal drugs used to treat the symptoms or causes of a disease.
The liver is the primary site for drug metabolism.

Which of the following gives the most accurate definition of a drug?

An addictive or harmful substance.
A substance taken into the body that modifies or affects chemical reactions.
A plant extract that kills bacteria.
A substance that produces side effects as well as therapeutic effects.

Antibiotics

Antibiotics are chemical substances made by certain fungi or bacteria that affect the working of bacterial cells.
They work by disrupting bacterial structure or function, or by preventing them from reproducing.
Antibiotics are effective against bacteria but not against viruses.
They target processes specific to bacterial cells, so they generally do not harm animal cells.

Which of these are true about antibiotics?

Antibiotics are effective against viruses.
Antibiotics can be produced by fungi.
Antibiotics target bacterial cell processes.
Antibiotics are effective against all microorganisms.

How do antibiotics work?

Antibiotics interfere with cellular processes in bacteria, either killing them or preventing their reproduction.
For example, penicillin prevents bacteria from forming cell walls.
Because viruses do not have cell walls and have different structures, antibiotics do not affect them.

Why does penicillin not affect viruses?

Viruses do not have cell walls.
Viruses do not contain cytoplasm.
Viruses become resistant to penicillin.
Viruses reproduce rapidly.

Antibiotic resistance

Overuse and misuse of antibiotics have led to antibiotic resistance.
Bacteria can evolve defence mechanisms, becoming resistant to antibiotics.
Resistant bacteria are known as 'superbugs', e.g. MRSA.
Factors include: prescribing for viral infections, not completing the course, and large-scale use in farming.

Patients should always complete the full ____ of antibiotics, even if they feel better, to reduce the risk of antibiotic ____.

How to prevent antibiotic resistance

Only take antibiotics when absolutely essential (prescribed by a doctor).
Always complete the full prescribed course, even if you feel better.
Do not use antibiotics for viral infections like the flu or common cold.

Which of the following is NOT a reason for antibiotics becoming less effective?

Doctors prescribing antibiotics for viral infections.
Patients always finishing their course of antibiotics.
Large scale use of antibiotics in farming.
Bacteria evolving defence mechanisms.

Plasmids and resistance genes

Bacteria can carry small circular loops of DNA called plasmids.
Plasmids can be passed between bacterial cells and may carry antibiotic resistance genes.
This allows resistance to spread rapidly among bacteria.

The small circular loop of DNA that can be passed between bacterial cells and carry antibiotic resistance genes is called a ____.

Antibiotic resistance mechanism

When antibiotics are used, susceptible bacteria are killed, but resistant bacteria survive and reproduce.
Resistant bacteria pass on their resistance genes to offspring.
Over time, the population becomes mostly resistant.

Which of these are ways to reduce antibiotic resistance?

Only take antibiotics when prescribed by a doctor.
Stop taking antibiotics as soon as you feel better.
Use antibiotics to treat viral infections.
Complete the full course of antibiotics.

Summary

Drugs modify chemical reactions in the body; the liver metabolises them.
Antibiotics kill or stop bacterial growth; they do not work on viruses.
Antibiotic resistance is a growing problem due to overuse and misuse.
Prevent resistance by using antibiotics responsibly and completing courses.

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