Lesson How Antibiotics Work

Quick Look

Grade Level: 9 (9-12)

Time Required: 1 hour

Lesson Dependency:

Subject Areas: Biology, Life Science

Photo shows young man looking into a medicine cabinet and holding a brown bottle of liquid medicine.
For antibiotics to work quickly, which delivery method works fastest: pills, liquids or shots?
Copyright © 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved.


Students are introduced to a challenge question. Towards answering the question, they generate ideas for what they need to know about medicines and how they move through our bodies, watch a few short videos to gain multiple perspectives, and then learn lecture material to obtain a basic understanding of how antibiotics kill bacteria in the human body. They learn why different forms of medicine (pill, liquid or shot) get into the blood stream at different speeds.

Engineering Connection

Biomedical engineers assist biologists and doctors in developing devices that allow us to observe cell interactions and reactions. They design artificial environments that simulate the body, and aid in the growth of cells. Other engineers, including mechanical, computer, materials and electrical engineers, collaborate to create the amazing array of devices and tools used in medical experiments.

Learning Objectives

After this lesson, students should be able to:

  • Describe how antibiotics kill bacteria cells.
  • Describe how medicine moves through the human body.

Educational Standards

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In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

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  • Determine the best approach by evaluating the purpose of the design. (Grades 9 - 12) More Details

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  • Compare different models to explain the movement of materials into and out of cells. (Grades 9 - 12) More Details

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(In advance, be prepared to show students three short video clips from the Internet.)

What happens in your body when you take an antibiotic? (Listen to student ideas.) Well, antibiotics are chemical substances that are given to people when they are sick with bacterial infections—with the intent that they'll make you feel a whole lot better.

(challenge question) Say one morning you don't feel very well, so your parents take you to see a doctor. The doctor suggests a generic antibiotic, and asks whether you would like to have the prescription filled in one of three ways: as a pill, in liquid form, or as a shot. Which delivery method should you choose? And, is there anything else you can do to feel better more quickly?

Today, we will generate ideas about what we may need to know about medicines and how they move through our bodies. By the end of the period, our goal is to reach the Research and Revise phase of the legacy cycle, learning exactly what antibiotics do when you are sick and which form of medicine you should choose to receive from your doctor or pharmacist—a pill, a liquid, or an injection/shot. Which one will get you feeling better the fastest?

(Continue by giving students five minutes to independently write on paper their answers to the following Generate Ideas questions.)

  • What background knowledge do you think we need to know to answer this question?
  • What do you already know from your own experience in taking medicines?
  • What steps should we take to answer this question?

(After five minutes, call on students to each share one entry with the class; list them on the classroom board.)

(Next, to gain Multiple Perspectives, show students three quick online videos that take less than five minutes total. The videos show an animation of bacterium cells being killed and/or medicine being introduced into the blood stream.

  • "Immune System – Natural Killer Cell," a 3:02-minute video about white cells, at http://www.youtube.com/watch?v=HNP1EAYLhOs
  • "Animation Details – Blood Absorb," a quick looping animation that shows red blood cells flowing through a vein and the diffusion of medication in through the wall of the vein, at http://animations.3d4medical.com/Blood-Absorb-animation_AN1262.html
  • "Animation Details – IV Injection 2," 6-second looping animation that depicts an intravenous injection into a blood vessel flowing with red corpuscles, at http://animations.3d4medical.com/IV-Injection-2-animation_AN1101.html

Then, verify that students have a general knowledge of how medicine works in the body.)

How does medicine work on cells? How does medicine move through the body?

(Guide students to generate more ideas from what they have seen.) From what you've seen, do you have any additional questions? Can you think of any additional information that is necessary or would be helpful to know in order to answer the challenge question? What else should we add to our list of what might be important to find out? (Guide students time to think about how medicine "flows" through the body.) What would we need to learn about the flow?

(As a class, categorize suggestions and develop an action plan. A possible research approach follows.)

  • Topic 1: How do antibiotics work? Gain a general knowledge of how antibiotics kill bacteria in the body, making you feel better.
  • Topic 2: How does medicine get into your system? Learn the effects of receiving medicine in a pill or liquid form, vs. a shot. Learn which method gets chemicals into a system more quickly.
  • Topic 3: How can we test what works best? What are microfluidics and how do we use them? Lean how engineers work with doctors to design and create miniature microfluidic devices used to do experiments to learn more about the delivery of medicine.
  • Topic 4: How can we get the medicine to move more quickly through the body? Study flow rate and distribution of particles. Learn flow rate equations and practice examples. See a microfluidics device particle flow video. Learn how to increase/decrease flow rate in the body.

(Moving to the Research and Revise phase, provide a short lecture to present more information on some of the topics listed, including how antibiotics work. Use the information provided in the Lesson Background section.) Tell me, how do antibiotics destroy bacteria?

(Proceed to conduct the associated activity Pill Dissolving Demo, a teacher-led class demo.)

Lesson Background and Concepts for Teachers

Legacy Cycle Information: This lesson covers the Challenge Question, Generate Ideas, and Multiple Perspectives stages of the legacy cycle, and begins the Research and Revise phase, during which students begin to compile their current knowledge, ideas and perceptions that they think are necessary to solve the challenge. Begin by briefly introducing students to the legacy cycle and how it applies to the unit. The purpose of this introduction is to help students understand why they are going through each phase of the cycle, and help them see how it relates to the engineering design process.

After students are given the challenge question (in the Introduction/Motivation section), have them generate ideas (write them on the board) and then show them three short videos (see online links in the Introduction/Motivation section) in order to acquire the multiple perspectives aspect. Then, give an explanation of how antibiotics work to inhibit and destroy bacteria, as provided in the lecture information.

Lecture Information: Antibiotics are chemical substances designed especially to inhibit or destroy bacteria, which are single-cell organisms that are all around us, including in our bodies. Most bacteria are harmless and offer beneficial functions to living things and humanity. But some can be harmful, and if they reproduce when the body's immune system is not working well enough to counteract them, they can cause diseases that make us feel bad.

Many types of antibiotics are available; each is a kind of selective poison that attacks a specific type of bacterium. Medicines can kill these bacteria in several ways. A drug might inhibit a bacterium's ability to turn glucose into energy or construct a cell wall. This causes the bacterium to die, without reproducing. Antibiotics can also stop a cell's ability to make more proteins.

When a person takes medicine orally, it must be dissolved in the stomach and transferred to the rest of the body via the blood stream. A pill can take about 30 minutes to begin working in a person's system. Doctors often prescribe pills because they are cost effective and have a long shelf life. Liquid medicines do not offer a quicker way to reach the blood stream (compared to pills), because the liquid must also be digested in the stomach before entering the blood stream. Shots given to patients provide much quicker relief, since the medicine is immediately injected into a person's blood stream, bypassing the digestive tract. An injection typically takes 10-15 minutes to take effect.

In the past, many drugs failed to work properly because they were poorly absorbed or were destroyed in the body, never arrived at the right place in the body, or were excreted from the body too quickly to have any effect. Today, most of those reasons are no longer problems because scientists better understand what happens to the chemical substances and what end products (by-products, side effects) result. They also have uncovered possible adverse cross-reactions when medicines interact with the compounds found in other medicines or vitamins, herbs, foods, and nutritional substances.

The formulation, packaging and delivery of medicines are tailored for optimal effectiveness, safety and convenience. This might include time-release capsules that provide a constant level of a drug over several hours or the packaging of acid-sensitive antibiotics so they can pass unaltered through the stomach into the small intestine where they are absorbed.

Associated Activities

  • Pill Dissolving Demo - During a class demonstration, students observe and measure the dissolution of three pills ("chalk" pill, gel pill, and gel tablet) in three beakers of vinegar, representing the acid in a human stomach.

    Watch this activity on YouTube


antibiotic: A chemical substance used to treat infections by destroying or inhibiting the growth of bacteria and other microorganisms.

bacteria: Single-celled microorganisms that can exist either as independent organisms or as parasites. singular = bacterium


Pre-Lesson Assessment

Discussion Questions: Ask students the following questions and discuss as a class.

  • How do you feel when you take medicine?
  • Have you ever noticed which form of medicine makes you feel the best?

Post-Introduction Assessment

Discussion Questions: As a transition to the associated activity, ask students the following questions and discuss as a class.

  • Were you surprised by how long it takes pill and liquid medicines to get into the human system (about 30 minutes, via digestive tract)?
  • What about different types of pills? Do you think gel and dry pills dissolve at different rates? Why? (This will be investigated in the associated activity—a teacher-led demo.)

Lesson Extension Activities

New and innovative delivery methods for medicines are being invented and tested all the time, such as pumps, inhalers, implants, patches and the covering of stents. Have student teams research these methods to find out their speeds, most suitable applications and why. (Examples: Pumps used for insulin, inhalers for asthma medications, implants for anticancer and pain medications, patches for estrogen replacement and smoking cessation treatments, and the covering of stents with the blood thinner heparin.) Another angle to explore: Does it matter at what time of day or whether oral medications are best taken with food or on empty stomachs?


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How Medicines Work Fact Sheet (30 Years Ago-Today-Tomorrow): Advances in Understanding a Drug's Journey through the Body. Last reviewed January 30, 2012; last revised August 2011. National Institute of General Medical Sciences, National Institutes of Health. Accessed February 28, 2012. http://www.nigms.nih.gov/Education/Factsheet_Drugs.htm


© 2013 by Regents of the University of Colorado; original © 2011 Vanderbilt University


Michelle Woods

Supporting Program

VU Bioengineering RET Program, School of Engineering, Vanderbilt University


The contents of this digital library curriculum were developed under National Science Foundation RET grant nos. 0338092 and 0742871. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.

Last modified: June 13, 2019

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