Using Technology to Study Cellular and Molecular Biology
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National Center for Research Resources

Using Technology to Study Cellular and Molecular Biology

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Teacher's Guide

Lesson 1—Engage, Explore, Explain

What Is Technology?

At a Glance

Overview

This lesson consists of two activities linked by classroom discussion. Its purpose is to engage students in the general topic of technology. The first activity involves classroom discussion and a short scenario to allow students to develop a sense of what technology is and to dispel the notion that technology relates mostly to computers. The second activity introduces students to the concept of scale by using the classroom to repre-sent a cell and other smaller objects to represent subcellular components.

Major Concepts

Technology is a body of knowledge used to create tools, develop skills, and extract or collect materials. It is also the application of science (the combination of the scientific method and material) to meet an objective or solve a problem. Scale is a way to represent the relationship between the actual size of an object and how that size is characterized, either numerically or visually.

Objectives

After completing this lesson, students will

Teacher Background

See the following sections in Information about Using Technology to Study Cellular and Molecular Biology:
1 Introduction
2 Major Preconceptions
3.1 Scale

In Advance

Web-Based Activities
Activity Web Version?
1 No
2 No
Photocopies
Activity 1 none
Activity 2 Master 1.1, Searching for Scale, 1 copy per student
Materials
Activity 1 none needed
Activity 2
  • meter stick
  • rulers
  • objects of various sizes (see Teacher note)

Preparation

Activity 1
No preparations needed.

Activity 2
No preparations needed.

Procedure

Activity 1: Technology—What’s It All About?

assessment icon
Assessment:
This activity is designed to engage students in learning about technology and to help the teacher assess the students’ prior knowledge of the subject.

Tip from the field test: Activities 1 and 2 can be conducted in several ways. You can engage the class as a whole in discussion as directed. Alternatively, you can divide the class into groups of three to five students each, ask each group to consider the questions you ask, and then have each group provide its responses. It is also possible to have student groups consider only a limited number of the questions and then handle the remainder with the whole class. If you choose either of the last two approaches, you should limit the time allotted for groups to consider each question to several minutes. Field-testing indicated that no approach was superior to another.

  1. Begin by asking the class, “How do you define technology?”

Accept all answers and write student responses on the board. Do not attempt to have students refine their definitions of technology at this point. They will revisit their definitions and refine them in Step 5. Students, like older individuals, may harbor the preconception that technology relates mostly to computers. Through advertisements and media articles, they are familiar with the terms information technology and computer technology.

Teacher note: Asking this question requires students to call on their prior knowledge, and it engages their thinking. At this point, do not critique student responses. Appropriate teacher comments are short and positive, such as “good” and “what else?” Other appropriate teacher responses include, “Why do you believe that?” or “How do you know that?” Questions such as these allow the teacher to assess students’ current knowledge about the subject and to adjust lessons accordingly. They also provide a springboard to “Let’s find out” or “Let’s investigate.” In general, it is time to move forward when the teacher sees that thinking has been engaged.

  1. Ask students, “In general, what does technology do for us?”

This question may help students understand that technology helps us solve problems, makes our lives easier, and extends our abilities to do things. Technology is used to develop skills or tools, both in our daily lives and in our occupations.

  1. Focus discussion on technologies that are relevant to each student’s life. Ask students to look around the room. What technologies do they see? How do these technologies solve problems and make their lives easier?

Accept all responses and write them on the board. Students may mention any number of items. Some may be school-related, such as binders, backpacks, pens, pencils, paper, and paper clips. Other items may be more personal, such as water bottles, personal stereos, and hair clips. Students may neglect items such as shoelaces, zippers, buttons, fabric, eyeglasses or contact lenses, makeup, and bandages. Discussion should reinforce the notion that humans develop technology with a specific objective in mind. A related concept is that a given task requires the right tool or tools.

  1. Pick a technology that students have mentioned. Ask them what types of knowledge were required to develop that technology.

Students may not realize that technologies are generally developed by applying knowledge from multiple disciplines. For example, producing today’s audio devices, such as a portable CD player, requires knowledge obtained from engineering, physics, mathematics, chemistry, and computer science.

  1. On the basis of previous discussions, ask students to rethink and refine their definition of technology (from Step 1).

Students should mention that technology is a way of solving problems through the application of knowledge from multiple disciplines.

  1. Tell students to imagine that they live in the Stone Age. Their only garment has been ripped and requires mending. How would they do it?

Students first should recognize that the ripped garment is a problem requiring a solution. They should consider what technologies they have available. The Stone Age was a period early in the development of human cultures when tools were made of stone and bone. Clothing consisted of animal skins or fabrics woven from threads derived from plant fibers. Bones and sharp reeds were used to make needles.

National Science Education Standards icon
Content Standard E:
Technological design is driven by the need to meet human needs and solve human problems.
  1. Ask students how their approach to mending the garment would change as time advanced from the Stone Age to the present. What new knowledge would allow the development of new technology?

Student responses will vary, and some students may want to jump directly from the Stone Age to the modern sewing machine. Slow them down and have them consider incremental changes in knowledge and technologies. They may cite the use of metals to fashion repair tools, like knives and finer needles. New knowledge of metals and chemistry would help here. Later advances in engineering and mechanics would lead to the development of human-run machines for assisting with repairs. Eventually, advances in physics (electricity) and engineering led to the invention of modern sewing machines. Similarly, advances in agriculture, chemistry, and engineering produced better fabrics and threads. Students should derive an understanding that technology advances through interactions among multiple disciplines. While a problem may remain basically the same over time (for instance, the need to make or repair clothing), advances in technology change how the problem is solved.

assessment icon
Assessment:
Listening to students’ responses will help you assess their understanding of the relationship between problems and technology.
  1. Write the words problem and technology on the board. Ask students to use arrows to draw a graphic that represents the relationship they believe exists between a problem and the technology to solve it.

They can use arrows of any kind, and they should be prepared to defend their suggestions. The graphic should illustrate that a problem does not drive technology unidirectionally, nor does technology exist solely in search of a problem to solve. Rather, these two areas exist to support and drive one another. Solving problems does require the development of new technologies, which can then be applied to other problems. A graphic to depict this indicates the cyclic relationship between the two:

Graphic of problem and technology, depicting the cyclical relationship between problem solving and the development of new technologies.

Activity 2: Searching for Scale

  1. Biological molecules are small, but how small is “small”? Ask students these two questions:
    1. How do biological structures, such as cells, organelles, bacteria, and viruses, compare in size with one another?
    2. How do molecules compare in size with biological structures such as cells, organelles, bacteria, and viruses?

Accept all responses and write them on the board. Students will explore these size relationships in the next steps.

  1. Tell students that they will now investigate the relative sizes of different biological structures and see how close their estimates of relative size were.
  2. Give each student a copy of Master 1.1, Searching for Scale. Work with the class to complete column 3, Size relative to cell.

The table with column 3 completed is as follows:

Biological
Structure
Actual Diameter
(in Meters)
Size
Relative to Cell
Object Used to Model
Biological Structure
Measured Size of
Model Object
Size Relative to
Model Cell (the Room)
Cell one times ten to the negative fifth power one times ten to the negative fifth power divided by one times ten to the negative fifth power equals one Room 10 m ten-tenths equals one
Bacterium one times ten to the negative sixth power one times ten to the negative sixth power divided by one times ten to the negative fifth power equals one tenth Desk 1 m one-tenth equals one-tenth
Mitochondrion five times ten to the negative seventh power five times ten to the negative seventh power divided by one times ten to the negative fifth power equals one-twentieth   0.5 m  
Virus one times ten to the negative seventh power one times ten to the negative seventh power divided by one times ten to the negative fifth power equals one-one-hundredth   0.1 m
(10 cm)
 
Ribosome one times ten to the negative eigth power one times ten to the negative eigth power divided by one times ten to the negative fifth power equals one-one-thousandth   0.01 m
(1 cm)
 
Protein five times ten to the negative ninth power five times ten to the negative ninth power divided by one times ten to the negative fifth power equals one-two-thousandth   0.5 cm  
Glucose molecule one times ten to the negative ninth power one times ten to the negative ninth power divided by one times ten to the negative fifth power equals one-ten-thousandth   0.1 cm
(1 mm)
 
H2O molecule one times ten to the negative tenth power one times ten to the negative tenth power divided by one times ten to the negative fifth power equals one-one-hundred-thousandth   0.1 mm  
National Science Education Standards icon
Content Standard A:
Mathematics is essential in all aspects of scientific inquiry.

  1. Tell students that the information in columns 2 and 3 each can be used to construct scales to describe the sizes of the different biological structures in the table. Ask students to define scale.

Accept all answers and write them on the board. Guide discussion so that students realize that scale is a way to represent the relationship between the actual size of an object (for example, its length or mass) and how that size is characterized either numerically or visually. A scale is a series of ascending and descending steps to assess either some relative (column 3) or absolute (column 2) property of an object. In this case, the property being investigated is size.

  1. Ask students to try to visualize the 100,000-fold difference in size between a cell and a water molecule. Can they do it? How could they demonstrate this large size difference more easily?

Master 1.1, Searching for Scale, provides the necessary clues for students, since the heading of column 4 is Object used to model biological structure. Students can use larger structures, such as a room, to model smaller ones, such as a cell, to make size differences more apparent and bring them into the realm of common experience.

  1. Ask two students to use a meter stick to mark approximately 10 m along both the length and width of the classroom.

It is okay if the classroom does not allow 10 m to be measured in either or both directions. A distance of 7 to 9 m will still make the point visually. However, for ease of calculations to follow, use room dimensions of 10 m even if the actual dimensions are smaller than that.

National Science Education Standards icon
Content Standard A:
Recognize and analyze alternative explanations and models.

  1. Tell students that the space defined by 10 m wide, 10 m in length, and the height of the room now represents a cell. In other words, this space is now a model for a typical cell.
  2. Organize students into pairs and give each pair a ruler.
  3. Tell students that they will be searching the classroom for objects that model the biological structures on Master 1.1, Searching for Scale.

Explain that they will be looking for objects that have the same size relative to the model cell (the room) that the actual biological structure has to a real cell.

assessment icon
Assessment:
Circulate around the room, noting whether students understand the mathematics involved in scaling objects for this activity.
  1. Ask students to look at the last three columns on Master 1.1, Searching for Scale. As an example, a desk measuring 1 meter high is provided as a model for a bacterium. Important points are as follows:
    1. A bacterium is one tenth the size of an actual cell (column 3).
    2. Similarly, the desk is one tenth the size of the model cell, the room (1 m compared with 10 m; columns 4 and 5).
    3. Because it is of the correct scale, the desk can be used to model a bacterium if a cell is modeled by a room 10 m across.
  1. Instruct student pairs to locate items in the classroom that can be used to model the biological structures listed on Master 1.1, Searching for Scale. They should enter their results in columns 4, 5, and 6 of the master. Allow 15 minutes for this activity.
assessment icon
Assessment:
Listening to student responses will help you assess their understanding of scale and modeling. Collecting their completed tables (Master 1.1, Searching for Scale) allows a more formal opportunity to evaluate students’ understanding.

Students may approach this activity in different ways. Some may find it useful to determine the size of the object they are looking for first by multiplying the ratio in column 3 by 10 m. Some students may begin by locating objects, measuring them, and then determining whether they meet the size requirements.

Teacher note: It is helpful to have objects available in the classroom that will meet the size requirements for modeling the biological structures in Master 1.1. Objects, such as erasers, marbles, fine- and ultrafine-tip pencils or pens, pieces of candy, an inflated balloon, balls of different sizes, and other easily obtained materials, ensure that students will be able to find something to serve as a model for each structure.

  1. Ask student pairs to share some of their results with the class.

Students should realize that the size ratios in columns 3 and 6 are the same. In other words, modeling allows relative sizes to be studied, although the actual sizes of the real biological structure and its model differ quite a bit.

Discussion Questions

  1. If a cell of 1 × 10–5 m (10 × 10–6 m, or 10 µm) diameter is represented by a room 10 m across, what distance would represent a human 2 m tall?

First, as in column 3 of Master 1.1, Searching for Scale, derive the relationship between the size of the human and the size of the cell:

2 meters ÷ (1 × 10–5 meter) = 2 × 105.

Thus, a 2-m-tall individual is 2 × 105 times larger than a cell 1 × 10–5 m in diameter.

If the cell is represented by a distance of 10 m, the 2-m-tall individual would be represented by a distance of

10 m × (2 × 105) = 2 × 106 m (2,000 km, or 1,250 miles)

As a reference, this distance is the same as that from Boston to Miami, Kansas City to Boston, or Los Angeles to Dallas. This calculation is intended to provide a “wow” for the students, and they derive an understanding of the difference in size between a human and a molecule (in this example, the difference between 2,000,000 m for the human and 2 to 5 mm for a protein). This should help students understand the need for specialized technologies for studying living systems at the cellular and molecular levels.

  1. As a lead-in to Lesson 2, write the following terms on the board in random order: Eye; Light Microscopy; Electron Microscopy; X-ray Techniques. Ask students to speculate on which technology (or technologies) could provide useful information about the objects on Master 1.1, Searching for Scale. What would make one technology more useful than another in any given situation?

Students should realize that naked-eye observation is useful only for relatively large objects and is not useful at all for discerning cellular and subcellular objects. They also will realize that light microscopy is useful for looking at cells and resolving some organelles, like the nucleus and vacuoles. Students should know from material in their texts that electron microscopy is used to provide details about cells and subcellular structures. Some may have seen electron micrographs of DNA. Most students know little about X-ray technologies, although they may have heard of X-ray crystallography as a technique that was used to help resolve the structure of DNA. If students have ideas about why certain technologies are better for some tasks than others, write those responses on the board. Indicate that the reason for having the right tool for the right task is addressed in Lesson 2.

Lesson 1 Organizer
Activity 1: Technology—What’s It All About?
What the Teacher Does Procedure Reference

Ask students,

  • “What is technology?”
  • “In general, what does technology do for us?”

Steps 1–2

Focus discussion of technologies relevant to each student’s life.

  • Ask students to look around the room; what technologies do they see?
  • How do these technologies solve problems and make their lives easier?
  • Pick a technology mentioned. Ask students what types of knowledge were required to develop that technology.
  • After discussion, ask students to rethink and refine their definition of technology.
Steps 3–5

Tell students to imagine that they live in the Stone Age. Their only garment is ripped and requires mending. Ask,

  • “How would you mend the garment?”
  • “How would your approach to mending the garment change as time advanced from the Stone Age to the present?”
  • “What new knowledge would allow the development of new technology?”
Steps 6–7

Write the words problem and technology on the board. Ask students to use arrows to draw a graphic that represents the relationship they believe exists between a problem and the technology needed to solve it.

Step 8
Activity 2: Searching for Scale
What the Teacher Does Procedure Reference

Ask students,

  • “How do biological structures, such as cells, organelles, bacteria, and viruses, compare in size with one another?”
  • “How do molecules compare in size with biological structures such as cells, organelles, bacteria, and viruses?”
Step 1

Tell students that they will investigate the relative sizes of different biological structures.

  • Give each student a copy of Master 1.1, Searching for Scale.
  • Work with the class to complete column 3, Size relative to cell.
  • Ask students to define scale based on the information in columns 2 and 3.
  • Ask students if they can visualize the 100,000-fold difference in size between a cell and a water molecule. How could they demonstrate this large size difference?
master icon

Steps 2–5

  • Ask two students to measure and mark approximately 10 m along both the length and width of the classroom.
  • Tell students that the space defined by 10 m wide, 10 m in length, and the height of the room is a model for a typical cell.
Steps 6–7

Organize students into pairs.

  • Give each pair a ruler.
  • Tell students that they will be searching the classroom for objects that model the biological structures on Master 1.1, Searching for Scale.
  • Tell students to use the information provided in the last three columns of Master 1.1 to help in their search.
  • Instruct students to complete the last three columns of Master 1.1 as they locate appropriate objects.
Steps 8–11

Ask students to share some of their results with the class.

Step 12
master icon= Involves copying a master.

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