1. © 2015 Pearson Education, Inc.

2. Introduction Cells have a cytoskeleton that
provides support and
allows some cells to crawl and others to swim.
Our understanding of nature often goes hand in hand with the invention and refinement of instruments that extend our senses.
© 2015 Pearson Education, Inc. 2

3. Introduction
In 1665, Hooke examined a piece of cork under a crude microscope and identified “little rooms” as cells.
Leeuwenhoek, working at about the same time, used more refined lenses to describe living cells from blood, sperm, and pond water.
Since the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.
© 2015 Pearson Education, Inc. 3

4. Chapter 4: Big Ideas Introduction to the Cell
Figure 4.0-2
Chapter 4: Big Ideas
Introduction to the Cell
The Nucleus and Ribosomes
Figure Chapter 4: Big Ideas
The Endomembrane
System
Energy-Converting Organelles
The Cytoskeleton and Cell Surfaces

5. Introduction to the Cell
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6. 4.1 Microscopes reveal the world of the cell
There is a variety of.
The first microscopes were light microscopes. In a light microscope (LM), visible light passes through a specimen, then through glass lenses, and finally is projected into the viewer’s eye.
Specimens can be magnified by up to 1,000 times.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. The Active Lecture Tip that follows suggests another related exercise.
Teaching Tips
 Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
 Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have a strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
Active Lecture Tips
 Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
© 2015 Pearson Education, Inc. 6

7. 4.1 Microscopes reveal the world of the cell
Magnification is the increase in an object’s image size compared with its actual size.
Resolution is a measure of the clarity of an image. In other words, it is the ability of an instrument to show two nearby objects as separate.
Microscopes have limitations.
Therefore, the light microscope cannot provide the details of a small cell’s structure
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. The Active Lecture Tip that follows suggests another related exercise.
Teaching Tips
 Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
 Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have a strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
Active Lecture Tips
 Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
© 2015 Pearson Education, Inc. 7

8. 4.1 Microscopes reveal the world of the cell
Using light microscopes, scientists studied
microorganisms,
animal and plant cells, and
some structures within cells.
In the 1800s, these studies led to cell theory, which states that
all living things are composed of cells and
all cells come from other cells.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. The Active Lecture Tip that follows suggests another related exercise.
Teaching Tips
 Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
 Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have a strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
Active Lecture Tips
 Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
© 2015 Pearson Education, Inc. 8

9. Figure 4.1a
Figure 4.1a Light micrograph of a protist, Paramecium

10. Figure 4.1b
Figure 4.1b Scanning electron micrograph of Paramecium

11. Figure 4.1c
Figure 4.1c Transmission electron micrograph of Toxoplasma

12. Figure 4.1d
Figure 4.1d Differential interference contrast micrograph of Paramecium

13. Figure 4.1e-0
10 m
Human height
1 m
Length of some nerve and muscle cells
100 mm (10 cm)
Chicken egg
Unaided eye
10 mm (1 cm)
Frog egg
1 mm
Paramecium
Human egg
100 μm
Most plant and animal cells
Light microscope
10 μm
Nucleus
Most bacteria
Mitochondrion
1 μm
Figure 4.1e-0 The size range of cells and related objects
Electron microscope
Smallest bacteria
100 nm
Viruses
Ribosome
10 nm
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms

14. 4.1 Microscopes reveal the world of the cell
Beginning in the 1950s, scientists started using a very powerful microscope called the electron microscope (EM) to view the ultrastructure of cells.
Instead of light, EM uses a beam of electrons.
Electron microscopes can
resolve biological structures as small as 2 nanometers and
magnify up to 100,000 times.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. The Active Lecture Tip that follows suggests another related exercise.
Teaching Tips
 Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
 Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have a strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
Active Lecture Tips
 Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
© 2015 Pearson Education, Inc. 14

15. 4.1 Microscopes reveal the world of the cell
Scanning electron microscopes (SEMs) study the detailed architecture of cell surfaces.
Transmission electron microscopes (TEMs) study the details of internal cell structure.
Differential interference light microscopes amplify differences in density so that structures in living cells appear almost three-dimensional.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. The Active Lecture Tip that follows suggests another related exercise.
Teaching Tips
 Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
 Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have a strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
Active Lecture Tips
 Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
Make a chart showing the four types of microscopes discussed so far showing the differences between them.
© 2015 Pearson Education, Inc. 15

16. 4.12 The small size of cells relates to the need to exchange materials across the plasma membrane
Cell size must
be large enough to house DNA, proteins, and structures needed to survive and reproduce, but
remain small enough to allow for a surface-to- volume ratio that will allow adequate exchange with the environment.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often think of the function of cell membranes as mainly containment, like that of a plastic bag. Consider relating the functions of membranes to our human skin. (For example, both membranes and our skin detect stimuli, engage in gas exchange, and serve as sites of excretion and absorption.)
Teaching Tips
 Even in college, students still struggle with the metric system. When discussing the scale of life, consider bringing a meter stick to class. The ratio of a meter to a millimeter is the same as the ratio of a millimeter to a micron: 1,000 to 1.
 Here is another way to explain surface-to-volume ratios. Have your class consider this situation. You purchase a set of eight coffee mugs, each in its own cubic box, for a wedding present. You can wrap the eight boxes together as one large cube or wrap each of the eight boxes separately. Either way, you will be wrapping the same volume. However, wrapping the mugs separately requires much more paper. This is because the surface-to-volume ratio is greater for smaller objects.
 The hydrophobic and hydrophilic ends of a phospholipid molecule create a lipid bilayer. The hydrophobic edges of the layer will naturally seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water (a simple cell). Furthermore, because of these hydrophobic properties, lipid bilayers are also self-healing. That the properties of phospholipids emerge from their organization is worth emphasizing to students.
 You might wish to share a very simple analogy that works very well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jellybeans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jellybeans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jellybeans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.)
© 2015 Pearson Education, Inc. 16

17. Surface-to- volume ratio 2 6
Figure 4.12a 1 3 1 3
Total volume
27 units3
27 units3
Total surface area
54 units2
162 units2
Figure 4.2a Effect of cell size on surface area
Surface-to- volume ratio 2 6

18. 4.12 The small size of cells relates to the need to exchange materials across the plasma membrane
The plasma membrane forms a flexible boundary between the living cell and its surroundings.
Phospholipids form a two-layer sheet called a phospholipid bilayer in which
hydrophilic heads face outward, exposed to water, and
hydrophobic tails point inward, shielded from water.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often think of the function of cell membranes as mainly containment, like that of a plastic bag. Consider relating the functions of membranes to our human skin. (For example, both membranes and our skin detect stimuli, engage in gas exchange, and serve as sites of excretion and absorption.)
Teaching Tips
 Even in college, students still struggle with the metric system. When discussing the scale of life, consider bringing a meter stick to class. The ratio of a meter to a millimeter is the same as the ratio of a millimeter to a micron: 1,000 to 1.
 Here is another way to explain surface-to-volume ratios. Have your class consider this situation. You purchase a set of eight coffee mugs, each in its own cubic box, for a wedding present. You can wrap the eight boxes together as one large cube or wrap each of the eight boxes separately. Either way, you will be wrapping the same volume. However, wrapping the mugs separately requires much more paper. This is because the surface-to-volume ratio is greater for smaller objects.
 The hydrophobic and hydrophilic ends of a phospholipid molecule create a lipid bilayer. The hydrophobic edges of the layer will naturally seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water (a simple cell). Furthermore, because of these hydrophobic properties, lipid bilayers are also self-healing. That the properties of phospholipids emerge from their organization is worth emphasizing to students.
 You might wish to share a very simple analogy that works very well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jellybeans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jellybeans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jellybeans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.)
© 2015 Pearson Education, Inc. 18

19. 4.12 The small size of cells relates to the need to exchange materials across the plasma membrane
Membrane proteins are embedded in the lipid bilayer.
Some proteins form channels (tunnels) that shield ions and other hydrophilic molecules as they pass through the hydrophobic center of the membrane.
Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.
Student Misconceptions and Concerns
 Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
 Students often think of the function of cell membranes as mainly containment, like that of a plastic bag. Consider relating the functions of membranes to our human skin. (For example, both membranes and our skin detect stimuli, engage in gas exchange, and serve as sites of excretion and absorption.)
Teaching Tips
 Even in college, students still struggle with the metric system. When discussing the scale of life, consider bringing a meter stick to class. The ratio of a meter to a millimeter is the same as the ratio of a millimeter to a micron: 1,000 to 1.
 Here is another way to explain surface-to-volume ratios. Have your class consider this situation. You purchase a set of eight coffee mugs, each in its own cubic box, for a wedding present. You can wrap the eight boxes together as one large cube or wrap each of the eight boxes separately. Either way, you will be wrapping the same volume. However, wrapping the mugs separately requires much more paper. This is because the surface-to-volume ratio is greater for smaller objects.
 The hydrophobic and hydrophilic ends of a phospholipid molecule create a lipid bilayer. The hydrophobic edges of the layer will naturally seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water (a simple cell). Furthermore, because of these hydrophobic properties, lipid bilayers are also self-healing. That the properties of phospholipids emerge from their organization is worth emphasizing to students.
 You might wish to share a very simple analogy that works very well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jellybeans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jellybeans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jellybeans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.)
© 2015 Pearson Education, Inc. 19

20. Hydrophilic regions of a protein Hydrophobic regions of a protein
Figure 4.12b
Outside cell
Hydrophilic heads
Hydrophobic tails
Phospholipid
Inside cell
Figure 4.2b A plasma membrane: a phospholipid bilayer with associated proteins
Channel protein
Hydrophilic regions of a protein
Hydrophobic regions of a protein